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

Printed Circuit Board Assembly & PCB Design Forum

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Open BGA joint



Open BGA joint | 15 September, 2004

Due to some reason there are few balls of the BGA left open during the process. Reflow profile has been verified. There are other BGAs on the PCB and they are fine too. The BGA in question has a very large metal heat sink on top of it and is placed right in the middle of the PCB. Is PCB warpage has to do something on it? The PCB runs on a fixture and on the mesh through the oven. Please advice..

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Open BGA joint | 15 September, 2004

It's going to be tougher to get the recipe correct on his bad dude. [As you'd expect.] But to start with, you need to run a channel of your profile on one of the open balls of this particular heat sinked BGA.

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Open BGA joint | 15 September, 2004

Once you verified for correct profile ( consider CTE mismatch) make sure before you remove PBA from fixture, the temperature is almost at room temperature. If by removing PBA from fixture,and the PBA gets a little bent (warped) just in the area where sBGA is located, solder joint apen can occour. We experimented similar problem on a 44 mm CBGA placed just in the middle of a PCB 400 mm X 350 mm (DfM?). We solved pbm by waiting for PBA cooling down before to remove it from fixture.

Regards GS

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Open BGA joint | 15 September, 2004

if opens in same aria check for mask to via coverage for that pad. We had vias pulling solder from pad. We did not have totally opens but capalry from via was as strong as capalry to ball / pad creating small joint aria.

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Open BGA joint | 17 September, 2004

What is the component ball co-planarity spec? I have encountered many ceramic and ASIC devices that specify 7 mil max.

If your stencil is 4, 5, 6 mil you WILL eventually have an open joint. You must deposit solder greater than or equal to your coplanarity spec.

ALSO, I have a device that warps 15 mils. I have video of this device (super BGA)on a hot plate...add heat will warp. Turns out the heat spreader attachment process is pre-stressing the device and is amplified in the smt furnace.

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Open BGA joint | 15 February, 2005

Ken, can U share your video information for the SBGA warpage?


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Open BGA joint | 24 February, 2005

GS, What should be the temperature we should get down to? Is it room temperature? Then it could be quite a long time. Eutectic solders cool down below 183C and may be cooling to 100C should do good? What do you think?

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