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BGA soldering problems

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BGA soldering problems | 24 November, 2008

I am having problems soldering a Rohs compliant BGA ATMEL AT91RM9200(rohs compliant board) This device recommends a soldering profile from J-STD-20 and a minimum peak package temperature of 250 centigrade,peak 260. However a lot of the other components on the board have a lower peak reflow temps, such as sanyo poscaps (240), watch crystals and littlefuse fuses (245). These components are very close to the BGA so it appears impossible to meet all criteria. Currently the reflow profile is peaking at 245 but we are seeing around a 10% failure rate with the BGA package with dry joints. The PCB has a very large unbroken ground plane on the outer layers, though not under the BGA. Will this affect the BGA soldering? Should I cut it back around the BGA.

All the Atmel BGA packages listed on the Atmel website specify that the ball composition is 95.5% Tin, 4% Silver & 0.5% Copper

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BGA soldering problems | 27 November, 2008

Hi Steve,

Are you actually profiling the BGA itself? By that I mean have you, for example, drilled through the underside of the pcb into the balls of the BGA and attached a probe there? You may find that even although the topside components have a peak temp of 245, there may be a significant difference at the BGA balls. The ground plane may also be acting as a 'heatsink' and drawing a fair amount of heat away from the BGA even though it only passes round it.

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