Components or PCBs due to poor quality production or contamination during lead-free assembly may cause nonwetting, so to ensure the product quality after assembly, it is therefore necessary to use the Solderability Test to verify the wetting quality of parts and PCBs.
Heat Resistance Test
Since the lead-free assembly temperature is approximately 40℃ higher than before, heat resistance testing is essential to test if active/ passive components and PCBs meet the requirements of reflow, wave, and soldering iron.
Moisture Sensitivity Test (MSL)
According to IST's testing statistics, approximately 40%~50% of ICs show signs of delamination due to moisture problems. In J-STD-020C Standard, lead-free component moisture is divided into six levels. Some Tier 1 customers internationally, only accept MSL 1 to 3; therefore, these components' designs and quality should meet the lead-free MSL criteria.
Tin Whisker Test
Tin whiskers will grow gradually as the product is used over time; therefore, components or FFC/ FPC containing matte-tin or tin-nickel must be tested for tin whiskers or else when the product is released to the market, tin whiskers will cause risks of shorts in the product. Currently, besides large companies having its own specifications, JEDEC/JESD201 standards are used internationally. Due to tin whiskers being as thin as hair fibers, testing and inspection should be in the same spot when conducting tin whisker testing or else improper handling will cause fragment resulting in misdiagnosis.
Procedure: Reflow Simulation→Environmental Test→SEM Inspection
Criteria: International companies use their own specifications; the JEDEC/JESD201 standard classifies the different grades: Class 1A (consumer electronics),Class 1 (industrial/ consumer electronics),Class 2(telecommunications/automobile electronics/ servers), and Class 3(medical/military).
Gas Corrosion Test
To evaluate connector joints and gold or silver plating ability to withstand gas corrosion, usually electrical resistance change is used as criteria. Failed samples can use EDX for failure analysis. Standards such as IEC, EIA, BellCore, ETSI have clear definitions, procedure, and conditions. For automotive usage, the environment is more crucial, so more attention on its ability and quality to withstand gas corrosion is required.
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PCB Bare board Testing: Glass transition temperature (Tg), Coefficient of Thermal Expansion (CTE), and T260/ T288 (Td) Test
High temperature assembly is in relation to glass transition temperature, thermal expansion, thermal stability, time of delamination of PCB, therefore, glass transition temperature (Tg), Coefficient of Thermal Expansion (CTE), and Td Test of bare board must be conducted.
2D/3D X-Ray on PCB Bare board
The quality of PCB will impact directly on the quality and reliability of lead-free products. Via plating crack, inner layer separation, blind via connection, popcorn / delamination, trace broken/crack, dendrite, and layout detection using 2D/3D X-Ray will ensure post-assembly quality.
SAT Inspection on PCB Bare board
T-scan inspection can is widely used to detect the PCB for popcorn, delamination, via plugging, laminate voids, which is a rapid, non-destructive way to locate anomalies.
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