PRINTEDBOARDHANDLING(ANDSTORAGE(GUIDELINES · PDF fileTo!preserve!the!quality!...
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PRINTED BOARD HANDLING AND STORAGE GUIDELINES An introduction by IPC D35 subcommittee member, Bob Lazzara
Transcript of PRINTEDBOARDHANDLING(ANDSTORAGE(GUIDELINES · PDF fileTo!preserve!the!quality!...
PRINTED BOARD HANDLING AND STORAGE GUIDELINES
An introduction by IPC D-‐35 subcommittee member, Bob Lazzara
To preserve the quality and reliability of PCBs during shipment and storage, military specifications and guidelines defined packaging methods
Prior to the IPC-1601
Many documents were • obsolete • incomplete • did not address lead-‐free assembly processes
• did not cover newer laminates or final surface finishes
Prior to the IPC-1601
Alternative surface finishes added concerns/requirements for PCB packaging & handling to preserve surface finish and assure solderability.
Prior to the IPC-1601
The IPC-‐1601 provides suggestions for proper: • handling • packaging materials and methods
• environmental conditions
• storage for PCBs
Scope and Intent
The 1601 intends to protect PCBs from: • contamination • physical damage • solderability degradation
• electrostatic discharge (ESD)
• moisture uptake
Scope and Intent
Moisture absorbed by PCBs will expand at soldering temperatures. The resulting vapor pressure can lead to: • internal delamination • excessive strain on plated-‐hole walls (e.g., post separation)
Scope and Intent
The 1601 covers: • Fabrication of the PCB • Delivery to Assembler
• Receiving the PCB • Stocking the PCB • Assembly & soldering
Scope and Intent
Targets these functions involving PCB…
• DESIGNERS • MANUFACTURING • ASSEMBLY • SHIPPING • STORAGE • WARRANTY
Information was supplied by individual serving all of these functions, as well as material and equipment suppliers.
Scope and Collaboration
PCB Raw Material Handling & Storage guidelines include: • Laminates • Handling and Foreign Object Concerns
• Environmental Concerns
• Inner Layer Production right: foreign object between inner layers, Drilling operation.
Guidelines for Fabricators: Raw Materials
Core Materials, Prepreg and Resin Coated Foils are sensitive to damage. Guidelines for handling & storage of prepregs and resin coated foils include: • Handle prepreg by the edges
using clean latex or nitrile gloves.
Guidelines for Fabricators: Raw Material Examples
• Store prepreg flat in a cool, dry environment (< 23 °C [73 °F], <50% RH).
• Reseal opened bags of unused prepreg.
• In cases where storage temperature is significantly below room temperature, allow prepreg to acclimate to ambient conditions prior to layup. Keep prepreg in a sealed package during the stabilization period to prevent moisture condensation.
• Do not fold prepreg.
Because moisture control is critical prior to inner layer lamination, key recommendations are made for the following: • Storage Conditions • Pre-‐lamination • Subcomposite Cores
(Sequential Lamination) right: edge-‐view of PCB, pre-‐press,
depicting two “cores” (green)
Guidelines for Fabricators: Etched Cores & Subcomposites
After the layers are pressed together, the 1601 continues with guidelines for the following areas and processes: • Processing Validation &
Control • Handling & Transport of
Product • Environment • Test • Inspection • Recommended Moisture
Levels Prior to Packaging
Guidelines for Fabricators: Post Lamination
Non-‐PCB Issues: • Phototooling • Temperature and Humidity
• Handling and Storage • Process Equipment • Capability
right: automatic solder mask coating system
Guidelines for Fabricators: Non-Product Issues
Temperature and humidity levels where photo tools are used & stored should be the same as where the photo tools were manufactured. Variation between areas can cause growth (moisture gain) or shrinkage (moisture loss).
right: light passes through photo-‐tool (black) casting the circuit image onto photo-‐polymer (blue)
Guidelines for Fabricators: Non-Product Example
PCB moisture sensitivity will depend on… • the resin system • details of design and construction
• assembly processes • soldering temperatures
…that the PCB will be exposed to by the Assembler.
Moisture Levels Prior to Packaging
Because verification may affect cost and schedule, limitations on moisture content prior to packaging should be as agreed between user and supplier (i.e., Assembler and Board House).
Moisture Content: Verification Agreement
Baking may be necessary to remove residual moisture absorbed into the PCB during the time between completion of the fabrication process and exposure to the assembly soldering .
Guidelines for Assemblers: Baking for Moisture Removal
If process controls are in-‐effective, the most practical remedy is baking. However, baking: • increases cost & cycle time • can degrade solderability • increase the likelihood of
handling damage or contamination
Problems Caused By Baking
Recommendations for PCB Baking Profiles
Packaging should include moisture barrier bags, desiccant to absorb any moisture that enters the bag, Humidity Indicator Cards to provide a visual indication of moisture level, and heat-‐sealing of the bag.
Recommendations for PCB Packaging
WVTR is the rate that water vapor passes through a specific area of barrier material. The WVTR for dry packaging PCBs should meet requirements of IPC-‐J-‐STD-‐033 (a WVTR of < 0.002 gm/100 in2/24 hrs.) A lower WVTR value may increase shelf life of the PCB, or reduce the amount of desiccant required.
Water Vapor Transmission Rate (WVTR)
The quantity and quality of the desiccant material selected should be in accordance with IPC-‐J-‐STD-‐033 and should be sulfur free.
About Desiccant
After going through the effort to prevent, mitigate and eliminate moisture, don’t keep moisture sensitivity a secret. Before you let it go, let the next person know.
Moisture-‐Sensitive Marking
Thank you for watching Introduction to the IPC-‐1601: Printed Board Handling and Storage Guidelines. Bob Lazzara VP, Technology BobL@Circuit-‐Connect.com (800) 560-‐9457, ext. 1 Circuit Connect, Inc.
Thank You.
