SLT Test Low Yield

Pin-Jet helped the customer determine the abnormal Pin Life time problem

The customer gave the feedback that the Pin Life time was approximately 70K; after confirmation by Pin-Jet, it was discovered that when the same PCB & socket was reassembled multiple times, the test results of each manual test were different. After investigation, it was found that the PCB pad was punctured and necessary to be replaced.

Problem Description

 ✔ Incident: User responded that the pin installation was abnormal.
 ✔ Test environment: Normal temperature
 ✔ Number of test sites: 12 sites
 ✔ Target: Confirm whether it is a pin issue that caused the low yield problem to occur.

Verification One: Adjust the Contact force + Socket cleaning experiment

 ✔ Purpose: Referred to the FT Handler setting and adjusted the SLT Contact force to 19kg, and confirm whether adjusting the contact force + cleaning socket can improve the low yield.
 ✔ Verification method
      1. Select the verification machine
      2. Contact force 15kg→19kg
      3. Cleaning method: Crystal brush + alcohol
      4. Monitor the yield changes of each site
 ✔ Verification result: Failed; adjusting the contact force + cleaning could not improve the low yield problem.

Confirm Again

 ✔ User proposed that reinstalling the socket can easily cause the contact to become unstable.
 ✔ The socket was reinstalled at site12 to verify whether there will be the problem of contact becoming unstable.
     Result of reinstalling the socket the first time: Fail
     Result of reinstalling the socket the second time: Pass
 ✔ Confirm whether the socket guide pin and test board guide hole have abnormal positioning problems: No abnormality
 ✔ Confirm that the test version was updated when the program was updated. Check whether there are abnormalities with the test versions online or in-stock:

Accessory Check: SLT Test Board
Actual confirmation of test board pad
Check result	The test board pad had wears and tears and punctures, and was determined to be C-~D according to the rules of the testing plant.

Comparative Analysis

FT LB and SLT Test Board Pad Comparative Analysis
	FT	SLT
Socket pin tail prepress value	0.15mm	0.15mm
Actual confirmation of pad
Comparative analysis	LB Pad had slight wears and tears, but still had its coating and the puncture marks were shallow.	The test board pad already had wears and tears and punctures; the puncture marks were deeper.
	B	C-~D

Conclusion

 ✔Comparative analysis results:

    Under the same socket and the same prepress value, the SLT test board pad already showed dents and wears and tears; it was determined to be class C-~D according to the rules of the customer’s plant. Contacts can easily become unstable.

 ✔Subsequent processing:

     1. It was confirmed that the SLT abnormality of this model was not a pin issue.

     2. The current SLT test board abnormality was proposed and the user will discuss the handling method with the customer later.