Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


PCB Thickness and BLR

Views: 1409

#82692

PCB Thickness and BLR | 3 June, 2019

Hi, I have a general question about the relationship of PCB thickness and BLR testing result. For example, I have QFN6x6 parts mounted on board in 1.2mm, 1.6mm, and 2.4mm thickness. All boards have 6 layers of Cu. Studies show thicker board gives less cycles to the first fail (worse BLR). What are the main reason(s) for that? I am also wondering if the thickness the same let's say 1.6mm but one board has 4 layers of Cu and the other 6 layers (all 1oz). Which one is more prone to fail? Thanks!

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#82879

PCB Thickness and BLR | 25 June, 2019

That is possibley CTE mismatch between QFN and PCB material, the thicker PCB the higher fail rate.

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#83059

PCB Thickness and BLR | 24 July, 2019

Typically, the reliability of PCBs suffers significantly due to the increase in aspect ratio. It is not preferred to opt for high thickness boards. However, I would like to point out that your assumption seems to be wrong as board layers do not directly impact BLR testing results.

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