IEC60749-25 - contents3

New product: Rapid-rate Thermal Cycle Chamber TCC-150W

Espec Technology Report No21 - 20 -

The current trend in electronics toward higher performance products that are smaller andlighter than ever before goes hand-in-hand with higher density mounting of increasinglyminiaturized semiconductor devices that contain more and more terminals. In addition, theenvironmental restrictions on the use of hazardous substances in electric and electronicequipment as mandated by the RoHS Directive in the E.U. have eliminated the use ofleaded solder. These societal changes are bringing about a stronger demand for moreprecision and accuracy in reliability testing. In response to this need for better reliability testing, we at Espec have developed theTCC-150W Rapid-rate Thermal Cycle Chamber. This model exhibits rapid temperaturechange of at least 20C per minute (average chamber temperature change with nospecimens), and offers high-performance temperature cycles with linear control capacity ata maximum 15C per minute with specimens.

Photo 1 The Rapid-rate Thermal Cycle Chamber TCC-150W

Toshifumi Nakasuji Environmental Test Business Headquarters, Business Control Department

Norihiro Kajiguchi Technical Development Headquarters, Technical Center

Topic 2 New product: Rapid-rate Thermal Cycle Chamber TCC-150W

Introduction 1



We previously noted that products now are higher performance as well as smaller and lighter than ever before, and contain higher density mounting of increasingly miniaturizedsemiconductor devices with more terminals. This situation creates new problems.

Higher density mounting of semiconductor devices has led to extremely high operating temperatures. Turning a device on or off creates a temperature cycle inside the equipment.This in turn creates repeated thermal expansion/contraction between the device and the PCB, causing the differences in the coefficient of thermal expansion of each material to produce thermal distortion, which creates stress on the solder joints. This process is a major cause of failure. (Refer to Fig.1.)

Fig.1 Stress on solder joints caused by temperature cycles

Device and mounting changes 2

2-1 Effects of the temperature cycle



Summary of standards Number of standard : IEC 60749-25 (JESD22-A104B) Name of standard : Temperature cycling Range of application : Solder joints of semiconductors and assembly PCBs Temperature range : -40/125C, 0/100C, -25/125C, etc. Temperature ramp rate : Specimen temperature max. 15C/min.

(10 to 14C/min. recommended)

The miniaturization of semiconductor devices and their increased number of terminals hasled to the change from QFP (Quad Flat Packages) to BGA (Ball Grid Arrays) and CSP (ChipScale Packages). (Refer to Fig.2.)

Fig.2 Device structural changes

New JEDEC standards (JESD22-A104B) have been issued for evaluating solder joints. When using these standards to evaluate solder joints in such applications as flip chips, BGA,and laminated packages, mild temperature changes are crucial to successful testing. Thesestandards specifically mandate a specimen ramp rate of a maximum 15C per minute. These standards have been incorporated into the IEC standards as of July 2003, and constitute a significant new method of evaluation.

2-2 Device structural changes

New test standards 3



The new model TCC-150W incorporates a specimen temperature ramp control function. Thermocouples are attached to the specimens, and the specimen temperature may be controlled linearly at a selected ramp rate. (Refer to Fig.3.)

Fig.3 Specimen temperature in ramp control

New product features 4

4-1 Specimen temperature ramp control



To keep the specimen temperature changes at the targeted ramp rate during the specimen temperature ramp control, specimen temperature changes are simulated and optimal air volume is determined. The heat transfer rate is crucial when using air as a medium for transferring temperature to the specimens. If the air volume is insufficient, theheat transfer rate will be too small to affect the specimens even if the chamber temperatureis changed. When test conditions call for a short soak time, the test may move on to the next cycle before the specimens have reached the targeted temperature. With optimal airvolume, specimen temperatures change in response to changes in the chamber temperature, the targeted ramp rate is quickly reached, and the targeted temperature is reliably attained. (Refer to Fig.4.)

Fig.4 Specimen temperature change at different air volumes

The IEC/JEDEC test standards prescribe the specimen temperature ramp rate at a maximum of 15C per minute (10 to 14C per minute recommended). Since conventionalchambers lack the capacity to control specimen temperature, performing tests in compliance with test standards required preliminary testing to monitor specimen temperatures. Also, careful adjustments were required to the test conditions and the quantity and placement of the specimens to insure that the specified temperature ramp ratefor the specimens would be attained. Now, using its specimen temperature ramp control, the TCC-150W has the capacity to simply and accurately perform the tests according to IEC/JEDEC standards by merely attaching thermocouples to the specimens.

4-1-1 Optimal air volume for specimen temperature in ramp control

4-1-2 Effectiveness of specimen temperature ramp control (1): Test adaptation to IEC/JEDEC standards



One crucial aspect of evaluating specimen life with temperature cycling is to attain uniformconditions of specimen distortion. Differences in the thermal coefficients of the different materials cause distortion in the specimens. Attaining a uniform speed at which this distortion occurs and attaining symmetry between the distortion waveform and the rise andfall in temperature are crucial to this test. Test dispersion is created when these factors differ with each test, and such tests exhibit poor standardization and reproducibility. Whentests exhibit dispersion, specimen life cannot be accurately determined. The TCC-150W allows the operator to set the ramp rate control for the specimen temperature, creating theability to attain uniform distortion speed and a symmetrical distortion waveform, providingaccurate specimen life evaluation. (Refer to Fig.5.)

Fig.5 Comparison of temperature waveform

4-1-3 Effectiveness of specimen temperature ramp control (2): Accurate specimen life evaluation capability



The TCC-150W has achieved dramatic improvement in temperature uniformity during temperature change. The model identifies optimum air volume and velocity uniformity through simulation and then attains those targets. Stress on the specimens can vary widelyduring temperature change due to differences in uniformity. Differences in stress due to specimen placement positions inside the chamber have been reduced to a minimum. (Referto Fig.6.)

Fig.6 Temperature uniformity data

4-2 Improved temperature uniformity



The TCC-150W attains a temperature change rate of 20C per minute (average chambertemperature with no specimens). This model is very useful for tests requiring fast temperature change, as well as for dramatically reducing test times. (Refer to Fig.7.)

Fig.7 Test time reduction

4-3 Fast temperature change capability



The TCC-150W complies with both JEDEC and IEC standards as well as a number of othertest standards.

Table 1 Major applicable standards Temperature setting

High temp.C Low temp.C Temperature change rate

Number of cycles

G +125 (+15, -0) -40 (+0, -10) I +115 (+15, -0) -40 (+0, -10) J +100 (+15, -0) 0 (+0, -10) K +125 (+15, -0) 0 (+0, -10) L +110 (+15, -0) -55 (+0, -10) N +80 (+15, -0) -30 (+0, -10)

IEC 60749-25 (JESD22-A104B)

O +125 (+15, -0) -25 (+0, -10)

15 C /min. or less

(specimen temp.)

1, 5, 10, 15min. after

specimen temp. attainment

Not specified

A +85 (+10, -0) -40 (+0, -10) 6.25 C /min. (specimen temp.) JESD22-A105B B +125 (+10, -0) -40 (+0, -10) 5.5 C /min. (specimen temp.)

10 min. after


1000

TC1 100 0 TC2 100 -25 TC3 125 -40 TC4 125 -55

IPC-9701

TC5 100 -55

20 C /min. or less

(specimen temp.)

10 min. after


200 500 1000 3000 6000

A +125 (+3, -0) -65 (+0, -5) IPC-TM-650 2.6.6 B +85 (+3, -0) -55 (+0, -5)

Not specified 30 min. 5

IEC-60068-2-14 Nb (JIS C 0025 Nb)

+1752 +1552 +1252 +1002 +852 +702 +552 +402 +302

-653 -553 -403 -253 -53 +53

10.2 C /min. 30.6 C /min. 51 C /min.

(Averaged over a period of not

more than 5 min.)

3 hours 2 hours 1 hour 30 min. 10 min.

(3 hours unless otherwise specified

in the relevant specifications)

2

IEC-61747-5 (EIAJ ED-2531A)

+1002 +952 +902 +852 +802 +752 +702 +652 +602 +552 +502 +452 +402 +352 +302

-503 -453 -403 -353 -303 -253 -203 -153 -103 -53 -03

1 0.2 C /min. 3 0.6 C /min. 5 1 C /min. (Averaged over a period of not

more than 5 min.)

3 hours 2 hours 1 hour 30 min. 10 min.

(3 hours unless otherwise specified

in the relevant specifications)

2

Compliance with test standards 5

Test standard Soak time



Table 2 shows the main specifications for the new model.

Table 2 Main specifications Model TCC-150W

Temperature control system Balanced temperature control (BTC) system Working temperature range +5 to +35C

Temperature range

-70 to +180C

Temperature fluctuation

0.5C (-70C to +180C) when temperature is stable

- 70 +180C No specimens (average chamber temperature change)

At temperature rise :22C /min. At temperature fall :18C /min.

Chamber Temperature

change - 40 +125C

Specimens :total 9 kg Glass epoxy PCB + jigs (Espec standard product)

At ramp control : 5 to 15C /min.

Performance *1

Specimen Temperature

change

- 40 +125C Specimens :total 9 kg

Glass epoxy PCB + jigs (Espec standard product) At ramp control : 5 to 15C /min.

Load capacity of specimen basket

5 kg per basket (evenly distributed) 7 shelves can be mounted

Test area dimensions W800 H500 D400 mm (effective test area) Loading capacity 160 L Outer dimensions W1000 H1808 D1915 mm

Weight Approx. 950 kg

Power supply

200V AC 3 phase 3W 50/60Hz

208V AC 3 phase 3W 60Hz, NEC spec. *2

220V AC 3 phase 3W 60Hz

380V AC 3 phase 4W 50Hz

400V AC 3 phase 4W 50Hz, CE spec.*3

*1: Performances are based on IEC 60068-3-5: 2001. *2: This equipment is in compliance with the requirements of the National Electric Code (NFPA 70)

for the United States of America. *3: This equipment is in compliance with the requirements of the European Community Directives.

Specifications 6



Our new product, the Rapid-rate Thermal Cycle Chamber TCC-150W, embodies a new product concept with its specimen temperature ramp control function. Temperature cycle tests now have the capability of meeting previously unattainable temperature test standards. We at Espec are offering a new test method with this model, which will serve asour new standard model. We believe that our customers will find that this model can play amajor role in improving product reliability and in improving productivity by reducing testingtime. Contact information For a catalog or more information on the TCC-150W Rapid-rate Thermal Cycle Chamber,

please contact the Espec International Business Headquarters or your nearest local Especdealer.

Conclusion 7

IEC60749-25 - contents3

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