Chapter OCV and OCR 3 - Keysight...The OCV is used to program the SJ-10 to recognise logos, signs or...

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Chapter

3

3.0 OCR and OCV

Chapter Contents

3.1 Optical Character Recognition (OCR) ..........................54 3.2 Optical Character Verification (OCV) ..........................55

Summary This chapter describes OCV and OCR, and how these features are set up.

OCV and OCR

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3.1 Optical Character Recognition (OCR) OCR is used to program a board to read printed text and is used as part of the inspection criteria. This is done using neural nets that are trained to recognise all number and capital characters. It should be used in the following cases:

• If it is difficult to detect a component, for example, if the component and the PCB background have the same brightness intensity, it can be used as a presence/absence test.

• To check for polarity • To detect specific text on a component body, which provides

information about the component., especially SOIC type components.

Switching on OCR Functionality OCR is enabled using the following steps:

1. Insert the following line into the config.txt file in C:\cpi\data: OCR 1 2

Note: Text in the config.txt file is case sensitive

2. Copy the files nn_ocr_default.txt and nn_ocr_default2.txt into the directory C:\cpi\data\ocr.

Note: These files are not found in the main directory structure. You must request them from MVT when required.

For information on setting and modifying OCR regions, refer to Chapter 3.

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3.2 Optical Character Verification (OCV) The OCV is used to program the SJ-10 to recognise logos, signs or any non-standard text on the body of a component, and is used as part of the inspection criteria. Its’ main aims are to determine if the correct logo or sign has been printed and/or to check the logo/sign for good quality printing. This is done by setting up a classifier directly related to a model or reference set. OCV should be used in the following situations:

• If it is difficult to detect a component, for example, if the component and PCB have the same brightness intensity, it can be used as a presence/absence test

• To check for polarity • To check for specific logo or sign on a component body, which

reveals information about the component, especially SOIC type components.

Switching on OCV Functionality OCV is enabled if OCR is switched on, as shown in previously. For information on using OCV and establishing an OCV region, refer to Chapter 3.

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Chapter

4 4.0 How to Train a Board

Chapter Contents

4.1 Overview.................................................................................... 58

4.2 Convert and Load PCB CAD Type......................................... 59

4.3 Run the SJ-10 GUI.................................................................... 61

4.4 Load PCB Onto the Conveyor Rail......................................... 66

4.5 Select PCB Type........................................................................ 67

4.6 Determine Board Orientation / Fiducial Location................. 68

4.7 Locate and Set the Fiducials / Begin PCB Inspection............ 69

4.8 Fiducial Parameters.................................................................. 72

4.9 Assign Device Types ................................................................. 82

4.10 Using Action on Failure Screen ........................................... 87

4.11 Editing Device Types ............................................................ 90

4.12 Training Untrained Components ........................................ 93

4.13 Add New Device Types ......................................................... 95

4.14 Setting the OCV and OCR Regions .................................... 98

How to Train a

New board

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Summary This chapter describes how to train and inspect a PCB. It is presented in a series

of steps, which makes it a little different to the rest of the manual, as the other

chapters are presented under a series of headings.


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4.1 Overview The SJ-10 must be trained (programmed) to fully inspect a new PCB type. Training involves carrying out a series of steps so that the SJ-10 can recognise and accurately locate all components on the PCB. There are two types of board:

• Good boards - have components correctly placed on them. • Bad Boards – do not have components placed on them but do

have paste deposits (in terms of pre-reflow) and have reflowed solder paste (in terms of post reflow).

Us the following step by step procedure to train a board: 1. Convert and Load PCB CAD Type. 2. Run SJ-10 GUI. 3. Load PCB onto the Conveyer Rail. 4. Select PCB Type. 5. Determine Board Orientation and Fiducial Location. 6. Locate and Set the Fiducials and begin an PCB inspection. 7. Assign Device Types. 8. Use Action On Failure (AOF) Screen. 9. Training Untrained Components 10. Add New Devices (Optional). 11. Set OCV and OCR Regions (Optional).

Access Levels This system is set up with two different user modes; Operator and Engineering mode. Each user mode allows different levels of access to the various functions and capabilities of the system. For moving between Operator and Engineer mode, see Step 2.

Note: Training of a PCB is done using the Engineering mode


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4.2 Convert and Load PCB CAD Type

CAD conversion To begin programming a new board on the SJ-10, its CAD must be converted into a format that the SJ-10 can use. This involves initially converting the CAD to a *.plx file format. The process is displayed in Figure 4.1.

Figure 4.1 CAD Conversion Chart

Note: The mentor neutral CAD data with geometry file is not used very often.

Three options exist for converting CAD to *.plx format: 1. Manually generate a file (use *.plx file specification – MVT

document 5000-0040). This should only be performed as a last resort.

The *.plx file should then be copied into the c:/cpi/cad/ directory using Windows NT Explorer or File Manager. Also if files are being copied from and existing or offline

machine, copy the *.plx and *.pls files also.


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2. Convert a Mentor Graphics Neutral file. MVT can provide a converter for this.

3. Convert a Gerber file for the solder stencil layer. GraphiCode’s GC Place software is used, and needs the Gerber file for the stencil. If the Gerber file is not an “extended Gerber” then an “aperture” file is also needed. If the GraphiCode option is selected, Reference Designators should be brought in. GraphiCode software can import file with the Reference Designators and XY locations, or can read the Reference Designators from a Gerber “ink legend” or “silk screen” layer.

Note: This is applicable only for mixed and gerber applications. All other PLX files are generated from CAD files (non-gerber). When generating a mixed application, the component *.plx file can be imported into GC Place and merged with the gerber. The Reference Designator can be merged or assigned with the gerber in this way


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4.3 Run the SJ-10 GUI Perform the following steps to select the board type and load a new board into the system: After the CAD file has been copied into the cpi directory, double-click on the SJ-10 icon on your desktop to run the SJ-10 software

Figure 4.2 Initialising Screen

There are two differnet modes to to select and they have different levels of access to the system associated with them. They are:

• Inspect Boards? – This is called the operator mode. • Train, Troubleshoot or Tune? – This is the Engineer mode.

This is displayed in Figure 4.3:


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Figure 4.3 Task Chooser Screen

To select mode, click icon

Note: To quickly change from Operator to Engineering mode and vice versa, Press Alt + tab to toggle or press on either the Operator or Engineer buttons in the taskbar.

1. The Engineer Mode should only be available to Engineers and is password protected. The username and password to enter the Engineering mode is as follows:

User Name: cpi Password: cpi602


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Figure 4.4 User Manager Dialog

Change Password Press the Change Password button in the User Manager dialog (see Figure 4.5) to change the user password. This is illustrated in Figure 4.5:


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Figure 4.5 Change Password Dialog

To change Password: 1. Insert your User Name (cpi). 2. Insert your Old Password (current password - cpi602). 3. Insert your New Password. 4. Confirm your New Password by inserting New Password

again. Press Okay button.

Create New User Press the Create New User button in the User Manager dialog (see Figure 4.4) to create a new user. The following screen is displayed;


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Figure 4.6 Create New User Dialog

To Create New User: 1. Insert Administrator Password, which is amt. 2. Insert New Users Privilege Level (Operator Level,

Engineering Level or both). 3. Insert New User Name. 4. Insert New User Password. 5. Confirm New User Password by inserting New User

Password again. Press Okay button.


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The following is the procedure used to set and configure fiducials on the PCB:

4.4 Load PCB Onto the Conveyor Rail 1. Press the E-Stop button (see Figure 4.8) and open the main

hood door. 2. Loosen the 2 thumbscrews at each end of the rail, push the

moving rail to the desired width, and tighten the thumbscrews. You can also do this by hand cranking the wheel.

3. Close the hood door and release the Emergency Stop button.

4. Load the PCB onto the outside conveyor in the correct orientation and it will enter the SJ-10 and be clamped for inspection.

Figure 4.7 Control Panel


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4.5 Select PCB Type Select the Boards option from the View menu in the Leftside Display Panel to bring up the list of boards on the system. To select the relevant board type simply double-click on the board icon or "drag and drop" the board onto the Main Display Screen

Figure 4.8 Main Display Screen


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4.6 Determine Board Orientation / Fiducial Location The correct orientation of the board in the SJ-10 conveyor must be determined. To do this click View in the Main Display Screen and then the View Board Graphic option. This displays the board orientation, location and number of the fiducials on the board.

What do Fiducials Look Like? Fiducial shapes can differ depending on the board manufacturer. The four most common fiducial shapes are circular, rectangular, diamond-shaped, and cross-shaped. Click on the relevant command button to match the shape of the fiducial on the board. The following values should be entered to match the shape of the fiducials on the board:

Note: For a cross-shaped fiducial the Ring and Centre Intensities are the same.

Figure 4.9 Dimension Parameters for Cross-Shaped Fiducials


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4.7 Locate and Set the Fiducials / Begin PCB Inspection The positions of the fiducials are setin order for the SJ-10 to accurately locate all component locations on a PCB. Once the first fiducial is located all other positions on the PCB are located relative to this point. Move around the board until you find the first fiducial. The fiducials on the board are differentiated by number (for example F1 = fiducial 1, F2= fiducial 2), and you must select the correct number for the fiducial in view. This is done using selection box, illustrated in Figure 4.10.

Note: Setting the fiducial position only needs to be done when a new board type is placed in the system for the first time.

Right Click on the Fiducial

Figure 4.10 Fiducial right click

menus

When you find a fiducial on the PCB and have established which fiducial it is, right click the centre of the fiducial (the red cross hairs should be positioned at the centre of the fiducia (or in the region thereof), and the menu illustrated left, is displayed.


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The Fiducial right click menu provides you with the following options: • Setting the fiducials as fiducial 1, fiducial 2 or fiducial 3 (There

are generally only two fiducials on a PCB). • Inspecting the fiducial 2 position (or fiducial 3 position). • Editing the fiducial parameters • Magnifying the field of view.

Set this point as: This menu option is used to set a fiducial as fiducial 1, fiducial 2 or fiducial 3. It will also allow you to run an AutoCheck to see if you have set the fiducials correctly (see Figure 4.11).

Figure 4.11 Set this point as Options

A u t o C h e c k

The AutoCheck option is used to validate whether you have set the position of fiducials correctly as illustrated in Figure 4.12 (a). If you use


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this option prior to setting the fiducials, the dialogue box illustrated in 4.12 (b) is illustrated.

(a) (b)

Figure 4.12 Fiducial AutoCheck Dialogues

Inspect (Go To) This enables you to automatically go to either fiducial 1, 2 or fiducial 3 once you have set correctly at least one other fiducial. This option is illustrated in Figure 4.13:

Figure 4.13 Inspect (Go to)


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4.8 Fiducial Parameters Fiducial parameters are configured using the Fiducial Editor which is explained below. Fiducial Parameters are divided into 4 classes:

1. Four region Sizes 2. Three brightness settings 3. Shape Mode 4. LEDs

Figure 4.14 Fiducial Parameters

Region Sizes(in microns) Table 3.1 describes the different region sizes and their relative functions: Region sizes

Function

Template X & Y

This green box defines the area in which the presence value is calculated. This is usually set at twice the size of the outer ring of the fiducial.

Inner X & Y Radius

This radius is used for presence calculation and should be set to be just smaller than the fiducial perimeter. It is blue in colour to identify it.

Outer X & Y Radius

This radius is used for presence calculation and should be set to be just larger than the fiducial perimeter. It is red in colour to identify it.

Search Area This yellow box defines the area in which the fiducial is


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X & Y expected to be found. This is usually set about four times the size of the fiducial to enable fiducial location even if the fiducial is offset. Unlike the other region sizes, which are radii, the Search Length is a diameter.

Table 4.1 Fiducial Region size parameters

Greyscale/Brightness Settings The user must input the intensity value corresponding to the brightness of the Background Intensity, Ring Intensity, and Centre Intensity. The valid range of brightness intensities is 0 to 255 as shown in Figure 4.15. Input the appropriate brightness to match the visible on-screen brightness of the Background Intensity, Middle Intensity, and Foreground and set the Presence Threshold.

Figure 4.15 SJ-10 Brightness Intensity Scale

Region sizes Function

Background Intensity

This represents the intensity of the PCB background and for a bright centred fiducial is generally 50.

Middle Intensity This represents the intensity of the fiducial centre and for a bright centred fiducial is generally 150.

Foreground Intensity

This represents the intensity outside the fiducial perimeter and for a bright centred fiducial is generally 250.

Presence Threshold

This represents the cut-off point for an acceptable presence score

Table 4.2 Fiducial Brightness Intensity Parameters


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Editing Fiducials Edit the fiducial by clicking Edit and then the Edit Fiducial option. This brings up the Fiducial Editor that displays the parameters used by the SJ-10 to locate the fiducials. This is illustrated in Figure 4.16.

Figure 4.16 Edit Fiducial

Fiducial Editor The Fiducial Editor is used to view and alter the parameters used by the SJ-10 for fiducial location and measurement. The goal in editing the fiducials is to obtain as high a Current Inspection Value as possible. The Current Inspection Value is a measure of how well the fiducial is being located. This value ranges from 0 (missing) to 1000 (perfect). Users should not settle for an inspection value less than 900 unless the fiducials are very dirty.


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Figure 4.17 Fiducial Editor Menu

Inspect Click on the Inspect option to inspect the fiducial after changes have been made to any of the parameters.

Autotrain Select Autotrain so that the fiducial parameters will be automatically trained. This may take a number of seconds.

LEDs On Click on this option to turn the LEDs on, off or auto during fiducial inspection. The LEDs may have to be on if the fiducials are dirty or oxidized.


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Editing Fiducial Parameters To edit the fiducial parameters, right-click on the centre of the fiducial and select Edit from the menu options displayed. The Fiducials menu, used to alter the fiducial parameters is displayed.

Automatic Fiducial Training Click on the Autotrain button to automatically train the fiducial parameters. If the Autotrain option is selected in the Fiducial Editor menu then this will already have been performed when the fiducial inspection failed. This usually takes about 10 seconds and provides a high fiducial score (approx.920). It is usually possible to obtain a higher score by manually editing these parameters.

Manual Fiducial Training Carry out the following procedure to manually edit the fiducial parameters.

1. Input the correct Shape Mode for the fiducial by clicking on the appropriate check box associated with a shape. i.e., ellipse, cross, square, or diamond

2. Turn the LEDs on or off. Turn LEDs on if fiducials are very dirty by clicking on the LEDs button. Turn LEDs off if fiducials are not dirty.

3. Set the correct fiducial dimensions to increase the Fiducial Inspection Value score

4. Set the Search box size so that it fits tightly around the fiducial.

5. For optimum results set the template area roughly equal to twice the outer ring area.

6. Set the Inner and Outer X & Y radii to differ by about 40 to 50 microns

7. Set the brightness intensities correctly. In general set the Background Intensity, Middle Intensity, and Foreground intensities to 50, 150, and 250 respectively, for a bright-centred fiducial.


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8. Exit the Fiducial Editor if the Current Inspection Value is high. A score of greater than 900 should be attainable. Do not settle for a score of less than 800 unless the fiducials are very dirty.

Fiducial Errors After performing an inspection, if the fiducial locations have not been found, the following message appears, as illustrated in Figure 3.20:

Figure 4.18 Fiducial Fail Dialog

The following buttons are provided with this dialog panel:


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This enables the SJ-10 to retry locating the fiducials

This option brings up cross hairs on the main display panel and the user should navigate around the board until the fiducials are located. If the location of the fiducial is unknown, then select the View Board Graphic option from the View menu

The Scale option allows the user perform an automatic scaling of the system. This is required if the camera height is changed, the camera is focused, or the aperture is adjusted or if a new product is introduced into the system.When you select this option you are brought to the Tools menu. You then need to select the Camera menu and click Automatic. For more information refer to Chapter 4. Note: An incorrectly scaled board manifests itself by the CAD being slightly offset from the centre of the components.

Clicking the Dismiss button exits the Fiducial Fail Panel.

What if the Fiducials do not line up? If the fiducials do not line up it may be due to one of these reasons.

• An incorrect board type has been selected. • The board is not properly positioned against the end stops. • The board may have been placed at the wrong orientation (180

degrees offset). • The fiducial parameters used to set the location of the fiducial,

needs to be edited.


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Poss ib le So lu t ions :

• Make sure the board is positioned against the end stops, the board is not warped, and that the correct CAD template is being used.

• Make sure the board has been placed the right way around. • If steps 1 and 2 do not solve the problem then the fiducial

parameters need to be edited.

Fiducial System Error This System Error is rarely displayed on screen, this message may appear on your Offline. The XY table has limits to it's X and Y movements, if the fiducial is outside it's limits of this movement then this error message will appear on screen. To fix this problem, ensure that the fiducials have been trained properly. and that the camera is not at the edge of the machine.This error is sillustrated in Figure 4.19.

Figure 4.19 Fiducial System Error Dialog


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Magnify from here by This enables the user to magnify the field of view. This may be useful to view board/component details closer.

Figure 4.20 Magnify Field of View

Perform an inspection When the board has been trained, click on the Inspect button on the main toolbar to perform an inspection. The results of the inspection are listed in the lefthand display panel. It lists the components that passed and the components that failed. This is illustrated in figure 4.21:


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Figure 4.21 Inspection Results


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4.9 Assign Device Types If a suitable device type is automatically selected, then select Assign Device by right-clicking the Device Type in the Training Assistant, this gives the option of assigning the Device Type to either the components Shape, Part Number or Reference Designator. Ideally the part should be ideally assigned by Shape or Part Number. Assignment by Reference Designator should only be used in special circumstances. For example, a situation where a component is placed very close to bright print on the board is best handled by creating a new Device Type with a smaller search area and assigning it to an individual component.

Note: Polarity checks can be added after this stage if the component requires it.

Assigning Device Types involves carrying out the following procedure step-by-step. Each step is described in greater detail later in this section.

1. Load the board, set the fiducial positions and click the Inspect button.

2. Jog through untrained components and stop at the component you want to assign a Device Type to.

3. Test a particular Device Type for suitability. 4. Assign a Device or a new Device Type to the component's

Shape, Part Number or Reference Designator. 5. If a Device Type exists in the Component Database, which is

a good match for the component, then assign this Device Type directly to the component.

6. If there is no Device Type in the Component Database, which is a good match for the component, then Assign a New Device Type, which is a Device Type that is the closest good match. This creates a duplicate Device Type of the first that must then be edited so that the New Device Type becomes a good match.


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7. Edit the Device Type if a New Device Type was assigned. (See next section – Assigning New Device Type)

8. Add Polarity Checks if you wish to determine if the component is placed at the wrong orientation. For more information, refer to the SJ Series Pre Reflow and Post Reflow Algorithms Manuals.

Note: Assignment by Reference Designator overrules that by Part Number and Shape. Assignment by Part Number overrules that by Shape. For more information, refer to Chapter 1.

Note:

Assigning New Device Type If a suitable match cannot be obtained, select a similar Device Type and using the Device Editor, edit it’s parameters. Right click a Device Type in the Training Assistant and select New Device, this option displays a dialog, where a new Device Type can be created. Enter a name for this new Device Type; (remember that the first letter of the name determines which algorithm type is used).


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Figure 4.22 New Device Type

• Select Edit Device by right-clicking the Device Type in the Training Assistant, this option displays the Device Editor, a device type’s parameters can then be edited to make it a suitable match

• Assign the new Device Type to the Shape, Part Number or Reference Designator of the component.

Testing the Suitability of a Device Type The suitability of a particular algorithm is based on various parameters. However as a General Rule the Device Template selected should be of similar size as the component and the Search Area (green box) should be just larger than the component. The factors that determine the specific suitability of a Device Type will become apparent later.


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Good Match

Bad Match

Figure 4.23 Chip Algorithm with Good Match and Bad Match Device Templates.

Note: Refer to the Post-Reflow Algorithm Manual (doc 5000-0090) and the Pre-Reflow Algorithm Manual (doc 5000-0089). These Manuals provide information on Post and Pre Reflow Algorithm’s.

Flag Device

Type Function

n Unknown Part

Designated as n0000. Used to identify components that have no Device Types assigned to them

r Resistor Used for chip resistors. c Capacitor Used for chip capacitors. t Transistor Used for 3-leaded transistors. q 4 Leaded

Transistors Used for large transistors that have three leads on one side and one lead on the other side

s SOIC Used for devices with symmetrical leads on 2 or 4 sides. This covers 4 and 5 lead SOTs, all SOICs, QFPs, TSOPs and PLCCs.

b Bright Box Used for Tantalum capacitors, shields, most connectors and switches. Can detect Bright or Dark components. This also denotes the Odd Part algorithm.


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e Local Fiducials

Used to locate local fiducials that are shaped like circles or ellipses or squares.

a Air Wound Coil

Used to locate four leaded components with a lead on each side in a cross configuration

x Cross Component

Used to locate four leaded components with a lead on each side in a cross configuration

d Statistics A simple presence / absence detection algorithm which can be used on very difficult components.

z Single Side SOIC

The Single Side SOIC Algorithm is a special vision algorithm used to locate and inspect components with leads on one side of its body only.

k Through hole

The through hole algorithm is a post-reflow algorithm used for through hole components, such as capacitors.

pa Paste The SJ-10 uses a blob tracking algorithm to locate and measure the paste on a board for 2D paste and also Mixed Mode application. To do this the SJ-10 takes two camera images of the paste deposit: one with (30 degree) low level LEDs and the other with the (80 degrees) top level LEDs.

Table 4.3 Algorithm types used by the SJ-10

Note: If a device type fails inspection, it’s parameters can be modified in the Device Editor menu which is described in Step.10.


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4.10 Using Action on Failure Screen If board errors were detected by the SJ-10 then the following features are initially displayed on screen:

1. Error images of defect components 2. Main Toolbar 3. List of Placement Errors.

Images of defect components After an inspection, images of the failed components are displayed on the Main Display Screen. By default, the maximum number of images that can be saved on screen is set to 12; however, there may be more defects present on the board then there are initially displayed on screen.

Figure 4.24 AOF Screen


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AOF Toolbar The AOF toolbar provides the user with the following options:

Figure 4.25 AOF toolbar

The “End Inspect” command button enables the user to exit from the Action On Failure Menu without releasing the board from the SJ-10.

Clicking on the “Repair” button releases the board downstream to the Repair station.

Clicking on "Previous" returns the user to the previous component viewed.

Clicking on "Next" brings the user to the next failed component detected during inspection.

This option allows the user to reinspect the current failed component. The Component Information tab will be automatically updated once this is selected.

Click on the Edit button to allow the user to edit a device type’s parameters. More information on editing device types is provided after this section.


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This option allows the user to mark a false fail if the SJ-10 incorrectly marks a component as having a defect when the component is good. This may occur if the parameters or thresholds are incorrectly set.

This provides the user with the option of rotating the CAD for individual Reference Designators, through 90 or 180 degrees. However, MVT recommend that all CAD changes be performed manually by editing the *.plx file.

Clicking the Toggle button switches the image of the component from dark to light.

Clicking the Skip button enables the user to delete the component permanently from the inspection. It writes the name of the skipped component to the Skip file and specifies that it is a skipped component by inserting an s at the beginning of the line. Components in that view which haven’t been skipped are also listed, and they are specified by a c at the beginning of the line.

Note: It is not recommeneded that this option is used often. Use the Alternative Type instead.

This option enables the user to omit a component temporarily from inspection. To reinsert, remake CAD.


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Click on this option to save an image of the failed component to the C:\cpi\img directory. By default these images will be saved in the following format in the "img" directory. The format will beeither *pgm or *ppm, where * represents the image name, which can be the Reference Designator, for example.

4.11 Editing Device Types Device Types can be edited using the following options: Select the Edit button from the Action On Failure toolbar or using the Trackball right click a component. By selecting a component using the Find command, right click the device Type in both the Standard and Advanced Search interfaces. From the View Board Graphic from the View menu, selct the component and right click. The goal in editing Device Types is to increase the Presence Score returned by the Device and have a large difference in presence scores when the component is absent and present The Device Editor Menu is used to edit Device Types and also to add Polarity checks to aalternate types and thresholdsThis is illustrated in Figure 4.26 and explained in more detail in the Pre and Post-Reflow manuals (Document Numbers 5000-0089 and 5000-0090 respectively). Also refer to chapter 3, which describes how to train a PCB.


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Figure 4.26 Device Editor Menu (Sample Settings)

For descriptions of the parameters in this menu , their associated range of values, and when to alter them, refer to the SJ Series Pre and Post Reflow Manuals (Document Numbers 5000-0089 and 5000-0090 respectively).


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After editing press Remake. Save the changes by closing the Device Editor menu and select Yes when prompted to save changes. Discard the changes made by selecting Reset.

Alternates The Alternates tab is used to assign multiple Device Types to components. It is particularly useful in the training of difficult components. The Alternates tab is illustrated in Figure 4.27:

Figure 4.27 Alternates Tab


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Note: For information regarding the Alternates Tab, refer to the Pre and Post-Reflow Algorithm Manuals (Document numbers 5000-0089 and 5000-0090 respectively).

4.12 Training Untrained Components

Figure 4.28 Board Tree showing untrained components.

From the Leftside Display Panel on the Main Display Screen, select Board and Untrained Components (refer to Section 2.3 – ‘Leftside Display Panel). The Engineer can then train the component by Shape, Part Number or by Reference Designator by right-clicking on one of the components listed.

• For example, select Train Part Number and a Training Assistant dialogue appears on screen.


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Training Assistant

Figure 4.29 Training Assistant Dialog

.

• Select the Algorithm Folder that contains the desired Device Type for the Component. The Component could be a chip or resistor etc.


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• Right-click on a Device Type and select Auto Choose. This will automatically select a suitable or similar Device Type. This will show the Device Template overlaid on the component image. Assign Device Type if an acceptable match is found or assign a similar Device Type if only a poor match is found. The procedure for doing so is detailed next.

4.13 Add New Device Types New Devices are added to the board by inserting a RefDes

Insert Reference Designator Inserting a RefDes is used by adding new device types to the board. In the past the .plx file had to be updated manually, but now this function updates the .plx file automatically. The Insert Reference Designator contains the following parameters: Shape: Enter the Shape of the component. SH_UNKNOWN is the default. Part Number: Enter a Part Number for the component. P_UNKNOWN is the default. Reference Designator: Enter a unique Reference Designator for the Device Type. Placement Machine: Enter the Placement Machine, the name of which can be found in the .plx file. Feeder Name: Enter the Feeder Name, the name of which can be found in the .plx file


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Orientation: Enter the Orientation of the component. There are four values to choose from the drop down menu. They are:

• 0 –North (default) • 90 –East • 180 – South • 270 –West

Device Type: Enter a unique Device Type name. The default is n0000. Location: The Location of the component is displayed in X, Y co-ordinates. To save and update the .plx and .pls files, click Insert. To discard the new Device Type, click Cancel. The Insert Reference Designator menu is illustrated in Figure 4.30:


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Figure 4.30 Insert Reference Designator


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4.14 Setting the OCV and OCR Regions Setting OCV and OCR Regions is optional. It is done by selecting the Insert option when you rightclick on a component that has alphanumeric or logos and unusual characters printed on it.

Insert Clicking on Insert brings up the dialog box illustrated in Figure 4.31. The following three options are available for selection:

• OCR Region • OCV Region • InsertRefdes.

Figure 4.31 Insert OCR Region


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The OCR Region allows you to train the the system to check text at component locations for the correct characters.. A general explanation of what OCR is and what it is used for is provided in Chapter 3.The OCR menu is illustrated in Figure 4.32

Figure 4.32 OCR Menu

The parameters and commands referred to above are described below.


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OCR Parameters Parameter Function Look for Text: * Specify the text on the component body that the

net is supposed to be looking for. Type the correct text against this parameter in capital letters

Pass for text (1) Specify the characters that the OCR expects to find on the component body for the component to pass inspection. This reduces the chances of the net returning a false fail. You must type the correct text in capital letters.

Pass for text (2) Specify a second string that the net will also use to pass inspection. This is an optional menu entry and must be entered in capital letters.

Require both filter texts

Set to true if both filter texts are required to pass inspection. It is set to False by default.

Orientation Specifiy the correct orientation of the characters. Set this to 0 for north, 1 for east, 2 for south and 3 for west. A green line is drawn on the side of the character that the OCR expects to be the bottom of the character.

Text is darker Set to True if you are looking for text darker than background. It is set to False by default.

Log results Prints the inspection results to a file. This name of this file is related to the Part Number of the current component in the cpi/data/ocr directory.

Multiple fonts Set this to True if you are using one neural network for the board.

Show Autosetup Details

Set to True to show training details of characters when autosetup is used.

Alternate is ‘Anded’

Set this to True if both initial OCR and Alternate OCR must pass inspection to pass full inspection

Table 4.4 OCR Parameters

Text Threshold slider is used to increase or decrease the brightness intensity threshold of dull characters. Values between –100 and +100


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should be entered to increase or decrease the threshold value above which the net expects all pixels to be text.

Figure 4.33 Text Threshold Slider

Text Height slider is used to set the height of the characters and to treat all blobs within a certain range of the text height as characters also. This is illustrated in Figure 4.34:

Figure 4.34 Text Height Slider

OCR List Menu is used to access the OCR Alternate Menu to define an alternate OCR analysis of the Part Number. The OCR Alternate menu is similar to the OCR menu. By setting parameters in the OCR Alternate Menu, an OCR Alternate Type is created.

This inserts an OCR Alternate in the OCR list.


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This button is used to delete the current OCR Region from the OCR list. Thics region can be the intial or the alternate OCR List.

This button is used to inspect the next alternative OCR type

This button is used to inspect the previous alternative OCR type. The Results box shows the results of the character recognition. The top line displays the character, and the bottom line displays the presence score associated with each character. This is illustrated in Figure 4.35:

Figure 4.35 Results

The Inspect icon is used to inspect the OCR on a component, using the original Device Type, after the OCR Region has been set


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Once the size and location of the Search Area has been set, users should press Autosetup and the net will suggest sensible values for several of the menu entries including Min. Char. Height, Orientation, and Mode. It is important to remember that this does not work in all cases and the parameters suggested should be double-checked by you carefully. A * acts as wildcard, where any character can be in place of *.

This is used to train the net to recognise a particular string. Once the correct value has been typed into the Image Box Text, Train should be pressed several times until the maximum presence scores are obtained. A score of over 90 should be attainable.

The user can train only one character among the blobs recognised by the algorithm. To do so, press Train One and then click with the mouse on the blob to be taught. A message is then displayed asking the user for the character corresponding to the clicked blob. A dialog box, as illustrated in Figure 4.36, prompts you to enter the correct character. Enter the character from the keyboard, which corresponds to the selected character.


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Figure 4.36 OCR Training Dialog Box

If different colour channels are available on the system, you can switch from one to the other to chose the image on which the inspection will be the best. This option is used to inspect components, which have dull text.

If different Neural Networks are available on the system, the user can switch from one to the other to chose the channel for which the text will appear best. This option allows more accuracy to the OCR algorithm, as the input size of the Neural Network can be increased.

The Other Part button is used to move to other components with the same part number.


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You should press Save once you are happy that the characters returned by the net are the correct ones, and when the presence score associated with each character is high, for example >90, although this value may not always be achievable.

S e t t i n g u p / E d i t i n g t h e O C R R e g i o n

The following steps show you how to set up/edit the OCR Region: 1. Access the OCR menu by right clicking on the search area of

a component on which to check text. Choose Insert OCR (if no OCR present for this component) or Edit OCR, if already present.

2. Choose a colour channel for which the printing is most visible by pressing Channel until results are satisfactory. Pressing Channel switches the light from red to green to blue.

3. Choose the Resolution of the Neural Network by pressing the Resolution button. The value of the chosen resolution is displayed; Low or High. By default, the resolution is set to Low.

4. Drag a box around the characters you want inspected. The Search Area should be just larger than the text in question.

5. Type in the Look for text field the text on the component body that you want the net to read (text must be inside the Search Area).

6. Press Autosetup so that the Algorithm will suggest values for the Orientation, Text Height, and Text. Setting Show Autosetup details to true will allow you to supervise the training, particularly if Pass for text fields have been filled. However, these values may be wrong so it is important to check that these parameters have been correctly set by checking the Results display.


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7. Input Boolean values in the different fields. Typically input True in Text is darker if text is darker than background.

8. Input a value between 0 and 3 for the orientation: 0 for North, 1 for East, 2 for South, and 3 for West. A green line will be drawn on the side of the character that the net expects to be the bottom of the character. Change value among the proposed choice until this green line is drawn on the bottom of the character.

9. Use the Text Height slider to input a value, i.e. the height of the characters in the text string. Make sure that sure that a red box is drawn around each character - THIS IS VERY IMPORTANT. If a red box is not drawn around each character you need to alter the Threshold parameter using the Threshold slider (value between –100 and +100). The Maximum size allowed by the Text Height slider is related to the size of the Search Area. The minimum size is the minimum size that must have a character to be trained by one of the two Neural Networks. That minimum size is bigger for a High resolution Neural Network.

10. Press Train a number of times until the Presence score associated with each of the characters is greater than 90 or use Train One to train only one character.

11. Type the character string or strings you wish the net to look for in Pass for text (1) and/or Pass for text (2).

12. In the eventuality of a component change or of a component having already an alternative inspection algorithm attributed, the use of OCR Alternate type is recommended.

13. If the Network results are satisfactory, press Save to save the network.

14. Exit the OCR Menu and save the data.


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Figure 4.37 OCV Menu

The following parameters are supported by the OCV algorithm:


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Parameter Function Logo Name Name of the logo/sign on the component body

that the net is supposed to be looking for. Distance Threshold Specifies the distance Threshold below which

the distance between the model and the current component needs to be for the component to pass inspection

Distance from Model Displays the calculated distance from the Model for the current component. If this figure is above the Distance Threshold, the inspection fails

Orientation Specifies the correct orientation of the logo/sign but is not required in the calculation by the classifier. Set this to 0 for north, 1 for east, 2 for south and 3 for west. A yellow line is drawn on the side of the logo/sign that the user sets as the bottom of the character. Input value between 0 and 3 until this yellow line is drawn on the bottom of the character (the location of north south etc. depends on the CAD).

Table 4.5 OCV Parameters

S e a r c h F a c t o r S l i d e r

This option allows you to increase the value of the loop looking for the logo/sign. Do this by increasing the value on the Search Factor bar. Set the Search Factor as illustrated in Figure 4.38.

Figure 4.38 Search Factor Slider


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The Threshold slider is used to increase or decrease the brightness intensity threshold of dull characters used by OCV. Values between –100 and +100 should be entered to increase or decrease the the threshold value above which the net expects all pixels to be text. This is illustrated in Figure 4.39:

Figure 4.39 Threshold Slider

To save theses settings, click Save Model

S e t t i n g U p t h e O C V R e g i o n

The OCV Region allows the user to train the board according to the logo or sign on the component body. A general description of OCV is provided in Chapter 3. The OCV menu is illustrated in Figure3.29: The following steps show you how to set up/edit the OCV Region:

1. Access the OCV menu by a right clicking on a component on which the search area appears and then by choosing Insert OCV (if no OCV present for this component) or Edit OCV.

2. Choose a colour channel for which the printing is most visible by pressing Channel until results are satisfying. Pressing Channel switches the light from red to green to blue

3. If a model has already been set and gives good results most of the time, increase values in Distance Threshold field and Search Factor field to allow more degrees of freedom to the


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OCV algorithm. Distance Threshold has generally to be less than 30 to give sufficient accuracy and the search factor must be greater than 1 and less than 200. If not, it is set to 20 by default. If the results are not satisfying or if a new Model needs to be set, proceed the following steps.

4. Press Reset Model to Reset the Model if a new model for the classifier is to be set.

5. Drag a box around the logo/sign to be inspected. The Search Area should be just larger than the logo/sign in question.

6. Press Inspect so that the logo/sign is inspected using the OCV tool. Ratio and Ratio Min-Rect are filled but not displayed on the screen. The Distance from Model is therefore calculated. The algorithm sets Search Factor to 20 by default.

7. If the position of the search is correct, press Save Model to save the current component as a model/reference. The 4 calculated parameters Max Height, Max Width, Aspect Ratio and Ratio Min-Rect become the reference parameters for the classifier without being displayed.

8. Input a value in the Distance Threshold field. The component will pass inspection if the value in the Distance from Model field is less than the one in the Distance Threshold field. A good degree of accuracy is generally performed with a Distance Threshold less than 30.

9. Input a value between 1 and 3 for the orientation: 0 for North, 1 for East, 2 for South, and 3 for West. A yellow line will be drawn on the side of the logo/sign that the user expects to be the bottom of the logo/sign. Input a value between 0 and 3 until this yellow line is drawn on the bottom of the logo/sign. This value is not required by the OCV algorithm to proceed with the classifier but can help the user visualising the orientation.

10. Input a string of characters in the Logo Name field. 11. Exit the OCV Menu and save the data


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Editing Device Thresholds Device Thresholds are edited by selecting the Thresholds Tab in the Device Type Editor.

Figure 4.40 Device Type Thresholds Editor Menu

The Thresholds menu contains the following parameters:


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Presence Threshold is the cut off point for an acceptable Presence Value. This will vary from algorithm to algorithm. A negative presence threshold means that the component should score less than the abslute value to be considered present. For example for a component with a threshold of –40, it needs to have a presence score of <40 to be considered present. Vertical and Horizontal are the cut off points for acceptable vertical and horizontal values.Thresholds are in Microns. Skew is in tenths of a degree (e.g. 60 is +/- 6 degrees). Joint 1 and Joint 2 are used to classify how a joint fails for being a bad joint. These have different meanings (and units) for each of the device types where post reflow inspection is enabled and will be shown in more detail for each algorithm.

Center of Bounding Box Chip Component

Bright End Contacts

Angle of Skew

Direction of Horizontal Offset

Vertical Offset for Left contact

Vertical Offset for Right Contact

Figure 4.41 How Offsets and Skew Results are Determined in

Chip Component (Example)


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Caution: Modifying Device Type Thresholds affects ALL Part Numbers and Shapes that are linked to that type. Check that all modifications are globally acceptable by thoroughly testing with populated and unpopulated boards. Do not make changes to the database to correct for a single troublesome component. Instead use some other method such as assigning a Device Type by Reference Designator (i.e. an algorithm for that specific component location) or by using Anded/Alternate types..

AOF statistics A number of important inspection statistics are displayed on the lower toolbar. The graphics monitor displays the location and status of the components on the board. The graphics monitor utilizes a colour-coding scheme to reveal the type of component error at a glance.

Figure 4.42 Graphics Monitor Display


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Colour Meaning White Good/Pass Red Missing Component – Bad

fiducial Cyan Bad joint, skewed component

panel Blue X-Offset Yellow Y-Offset Magenta Unknown/Omitted part

Table 4. 6 Graphics Monitor Colour Coding

Also displayed on the graphics monitor (above) is a Bullseye Chart and an Axis Histograms that shows the mean X and Y offset of the components and/or deposits on the PCB. A circle of radius 150 microns is drawn on the Bullseye Chart to give an indication of the offsets involved. In addition, statistics are presented on the top left-hand corner of the monitor that detail the overall mean X and Y offset and skews of components on the PCB (with their standard deviations included).

Chapter OCV and OCR 3 - Keysight...The OCV is used to program the SJ-10 to recognise logos, signs or...

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