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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Wafer Reflow Profile

Susan

#12747

Wafer Reflow Profile | 1 February, 1999

Hello Everybody:

I am in urgent need of some information regarding the reflow profile for a flip chip wafer. Would the reflow conditions along with the flux used affect the appearence of the solder joints.

We are witnessing dull solder joints after wafer reflow, which causes some placement issues. I would really appreciate if anyone of you would advise me about it.

Regards Susan

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Chris G.

#12748

Re: Wafer Reflow Profile | 2 February, 1999

| Hello Everybody: | | I am in urgent need of some information regarding the reflow profile for a flip chip wafer. Would the reflow conditions along with the flux used affect the appearence of the solder joints. | | We are witnessing dull solder joints after wafer reflow, which causes some placement issues. I would really appreciate if anyone of you would advise me about it. | | Regards | Susan | Susan,

No answers for you yet, just questions. Why are you bumping the wafer and not your supplier? Are you bumping using a stencil? What is the base metal of the wafer? What solder composition are you bumping with. If wafer metal is gold. The rate at which the gold dissolves into the solder will increase as the reflow temp increases. If the wafer pad is gold, and the gold constitutes a large percentage of the solder joint, you will have week, very grainy solder joints. What problems are you having at placement due to dull solder joints. I suspect a vision recognition problem.

Very interested in what you find out and what your process is. Have investigated this in the past but always run into the gold imbrittlement problem due to wafer pads being way too thick with gold.

Thanks,

Chris G.

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Justin Medernach

#12749

Re: Wafer Reflow Profile | 2 February, 1999

| Hello Everybody: | | I am in urgent need of some information regarding the reflow profile for a flip chip wafer. Would the reflow conditions along with the flux used affect the appearence of the solder joints. | | We are witnessing dull solder joints after wafer reflow, which causes some placement issues. I would really appreciate if anyone of you would advise me about it. | | Regards | Susan | I trust you're using a C4 collapse for a process. Are there any special metals involved. EG. Gold or palladium. Silicon is a good conductor of heat. Temperature on top of the chip should be very close to that underneath it so you can at least get a rough approximate of a profile by thermocoupling the top of the device.

Regards, Justin Medernach

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Jon Medernach

#12750

Re: Wafer Reflow Profile | 2 February, 1999

Chris is correct. You will have a problem if you do not have the right metalization under your bump. The BM is critical, it is defined by the passivization layer on top of your die much like a solder mask defined interface on FR4. You will find most of the information on Bump Metalization to be proprietary. Have you considered stud bumping?

Hello Everybody: | | I am in urgent need of some information regarding the reflow profile for a flip chip wafer. Would the reflow conditions along with the flux used affect the appearence of the solder joints. | | We are witnessing dull solder joints after wafer reflow, which causes some placement issues. I would really appreciate if anyone of you would advise me about it. | | Regards | Susan |

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Reflow Oven

reflow oven profiler