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Pasteproblemater aftersoldering

#32460

Pasteproblemater aftersoldering | 6 February, 2005

can some one give me some suggestion to solve the problem. we are using cooksun/alphametal rma9086 paste for our screenprinting. after the reflow we see lot of solder ball on the board. we have maintained the exact profile given by the manufacurer. we are using stensil of 10 mil thickness. this solder balls are seen on the PCBpads adjustant to another pad which causes shorts.

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#32461

Pasteproblem after reflow | 6 February, 2005

can some one give me some suggestion to solve the problem. we are using cooksun/alphametal rma9086 paste for our screenprinting. after the reflow we see lot of solder ball on the board. we have maintained the exact profile given by the manufacurer. we are using stensil of 10 mil thickness. this solder balls are seen on the PCBpads adjustant to another pad which causes shorts.Is this solder paste problem or process problem?

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GC

#32462

Pasteproblem after reflow | 6 February, 2005

Please try to use 6-8 mils ..you are overloading pads surface ..Please verify paste volume vs surface..Have fun

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ET

#32465

Pasteproblemater aftersoldering | 7 February, 2005

Reducing the Printing Speed helps to reduce solder balls. Try it.

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Chunks

#32468

Pasteproblemater aftersoldering | 7 February, 2005

This paste does tend to solder ball - but short of changing paste you can change your stencil to accommodate it. First, why 10 mils? Seems very thick. What size parts are your working with?

Typically you can �homeplate� the R�s and C�s and this will eliminate any solder balling, unless your ramp rate is very fast, but this creates more solder ball spatter. Sounds like you�re getting a big ball next to each component. The homeplatting should eliminate this, although I�ve never tried it on a 10 mil stencil.

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#32469

Pasteproblemater aftersoldering | 7 February, 2005

Search the fine SMTnet Archives for previous discussions on the issues driving solder balling.

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JB

#32470

Pasteproblem after reflow | 7 February, 2005

I agree, a 6 mil stancil plus reduced apertures will help.

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Indy

#32471

Pasteproblem after reflow | 7 February, 2005

1. use 6-7mils stencil. 2. reduce aperture opening to 60-70% of pad size. 3. check viscosity of solder paste. According to that you might want to alter your print speed and pressure.

Cheers Indy

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dhanashekar

#32484

Pasteproblem after reflow | 8 February, 2005

we have even tried with 6mil stencil even than we are getting the solder ball thanks for your suggestion

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Dougs

#32489

Pasteproblem after reflow | 8 February, 2005

have you had any reduction in aperture size though, we generally use a 6 mil stencil thickness with a 10% aperture size reduction for chip components and leaded components ( SOIC - QFP ) and a 1:1 ratio for BGA components without any problems.

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DasonC

#32502

Pasteproblemater aftersoldering | 8 February, 2005

Beside, what is your paste handling and storage condition?

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dhanashekar

#32507

Pasteproblemater aftersoldering | 9 February, 2005

we are storge the soldering past as per the manufacture sefaction of arround 5deg before the using the paste we remove the paste from the storge and keep the paste in the room temp and then used. THANKS for the your soulation if ane other sulation please let me now.

REGARDS Mr. Dhanashekar

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#32559

Pasteproblem after reflow | 10 February, 2005

thanks for your reply i have to try with a stencil wirh reduced aperture opening

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