0.5mm CSP Reliability

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It is CSP reliability issue, which is the mobile CPU from Sp... - Apr 23, 2008 by fowlerchang

Use of a hot air gun to reflow solder that passes tests [aft... - Apr 24, 2008 by davef

We have measured the temperature of CSP solder joint. The pe... - Apr 24, 2008 by fowlerchang

Please post a picture of your cross section. ... - Apr 25, 2008 by davef

fowlerchang

#54477

0.5mm CSP Reliability | 23 April, 2008

It is CSP reliability issue, which is the mobile CPU from Spreadtrum.

All the tests passed and shipped to customer. They assembly them and tested but failed. After they reflow this CSP with hot air gun, some of the boards passed.

We got some boards to do cross section and dye penetration. No evidence of solder joint crack were found after failure analysis.

This CSP is 0.5mm pitch without underfill process. It is a lead free component, and we try them with leaded and lead free solder paste. But same problem happened.

We doubt whether it is component or design problems. But we don��t know what��s the next step.

Thanks! fowlerchang@rayval.com

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davef

#54488

0.5mm CSP Reliability | 24 April, 2008

Use of a hot air gun to reflow solder that passes tests [after failing those tests] seems to indicate the standard process reflow was inadequate. To understand this better, we'd want to measure temperatures at various points on the board during reflow. Certainly, one of those points would be on an inner ball of the CSP. We'd like this ball to be one attached to a thermal sink, such as a ground plane or power line.

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fowlerchang

#54489

0.5mm CSP Reliability | 24 April, 2008

We have measured the temperature of CSP solder joint. The peak temperature is 232oC and the wetting time above 217oC is 30s. But we use leaded solder paste instead of lead free solder paste.

I doubt why no crack of solder joint was observed after cross section.

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davef

#54492

0.5mm CSP Reliability | 25 April, 2008

Please post a picture of your cross section.

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