A secret they will not tell – Why 10u”au PCB oxidized in less than 1 year?

BY:Magi Mole
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This is a case that happens often.  The buyers purchased the PCB with 10u” gold plated and installed into their machines to delivery to the market.  Less than one year later, the machines kept being rejected by customer one by one.  The Engineer found out the invalid PCB and checked the surface in the LAB.  These invalid PCB were not as flash as the normal one.  They checked the PCB under EDX and a lot of spots were found on the surface of gold pated area. This was the “killer” who killed the PCB.


After further material analysis of the spots, they belonged to Oxide and sulfide groups.  The result told us that there’re trace amounts of residual sulfides on PCB after surface treatment.


But, why 10u” gold was oxidized in such a short time?  Factory in China offered a report that said gold plated thickness was 5u-10u”.  And factory declared that was a general spec in China. What is wrong here?


The original spec of Gold plating, in the worldwide, is that 10u’ gold means “Minimums 10u” gold”.  No compromise.  Since the gold price increased 60% in 2009-2012, the gold plating spec was silently changed to start from minus 3-5u”.  It became a commend spec in Asia too, not only in China.  There are still some companies who are following the Original Spec (in minimum value), such as the factories in zugo e-commerce platform.


In this case, the Spec so called by factory 5-10u” gold is equal to Original Spec 5u” gold only.  After the Salt Spraying Test, here is the test result that you may know how different they are.


The plating spec factory said 10u”(actially is  5u" in Original spec) was showed on yellow background.  In 96hrs test, it lost the flash of gold; the black spots came out after 120hrs.  And it got worse after 168hrs.  That was why it oxidized in less than 1 year. This was also a reason that E-Waste increased so sharping from 2012 till today. 


Our sincere advice for you:

* Don’t forget to clarify the spec with your factory in sourcing stage.

*You must request the gold plated report from your factories before delivery.















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