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mirco bga stencil opening

ck

#21499

mirco bga stencil opening | 12 September, 2002

Hi all, Any stencil opening recommendation for 20mils pitch mirco BGA. Currently, using 12mils round opening, 5 mils thickness. Seen to have weak joints as it crack after Ict testing.

thks

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michael houghton

#21502

mirco bga stencil opening | 12 September, 2002

I have printed and placed similar devices in high volume with exactly this spec for a couple of years with no problems, are you using laser cut stencils and what type of solder paste are you using? and what is the end use of the product as it may need underfill depending on application even when your process is with out cracking.

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michael houghton

#21503

mirco bga stencil opening | 12 September, 2002

I have printed and placed similar devices in high volume with exactly this spec for a couple of years with no problems, are you using laser cut stencils and what type of solder paste are you using? and what is the end use of the product as it may need underfill depending on application even when your process is with out cracking. What about your reflow profile are you using RSS RTS have you checked with thermocouples under BGA device

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Pete B

#21504

mirco bga stencil opening | 12 September, 2002

We have used a laser cut stencil 0.15mm (0.006") thick with 0.3mm (0.012") square apertures radiused in the corners 0.06mm (0.0025") to aid paste release. This approach with the (type 3) paste we use has proven successful on thousands of devices placed over the last 18 months or so. This additional past volume gives a little more compliance in the soldered joint and we have had no failures of the joints themselves.

Some questions:

1. Where are the cracks you are seeing occurring, at the ball/PCB interface, the ball/device interface or in the bulk solder?

2. Is the device located on an area of the circuit that is subjected to flexure during ICT?

3. What kind of solder paste are you using and what is your reflow profile?

Regards,

Peter Barton

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#21506

mirco bga stencil opening | 12 September, 2002

CK, If joints have been validated prior to ICT (under BGA Scope), more often than not repeatable joint fractures are due to undo stress being placed on the component during ICT test. Verify ICT probes and fixture. If after proving out fixture/pin compliance, next look at the land finish. If gold, embrittlement could be occuring. First step would be to inspect/validate the finish per IPC standards. Your PCB supplier should be able to help you with this. Any additional questions, please feel free to contact me. Scott

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Pc

#21748

mirco bga stencil opening | 25 September, 2002

Try .005 or even .004 thick laser cut electopolish stencil and reduce grain size of paste. Go with 400 or 25 in the case of AIM. We had a similar prob.

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Eric

#21815

mirco bga stencil opening | 2 October, 2002

See Fiske first line. I'd bet You are bending or catching the assembly in the ICT. How many probes at 8OZ each? do you use on that ICT? 800 probes = 400lbs. See "Flexure induced failure of BGA solder joints" by Compaq Houston TX

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CH

#21840

mirco bga stencil opening | 6 October, 2002

Hi Eric, How to access to the Compaq Houston reprot.

regds

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Pavel

#21871

Help for soldering mirco bga | 9 October, 2002

Dear colleagues. I ask you to prompt me about necessity of drawing pastes through a stensil at the soldering micro BGA with step between leeds 1 mm and 0,8 mm or uses only a flux for this purpose. And what most suitable paste for the soldering of such components? What sizes of apertures on a stensil?Where it is possible to find the literature under the soldering micro BGA and Flip Chips?

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Chris Dill

#21956

Stress On BGA | 15 October, 2002

Stress analysis on a component is available ECT (fixture house)

Feel free to contact me @ (401)739-7320 x3337 for info.

Chris

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