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Solder balls

Views: 3591

#55521

Solder balls | 15 July, 2008

Hello everyone,

I have too much solder balls in my smt process recently. Can you help me with some ideas.

Equipment: DEK, UIC AdVantis, Vitronics(10zones-> 8+2cooling) paste Aim NC254

Thanks in advance!

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#55528

Solder balls | 15 July, 2008

Can you describe your solder balls...mid-chip solder balls, "splatter" around pads, etc.?

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#55576

Solder balls | 17 July, 2008

I would say the balls are aminly on passive parts in the middle.

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#55580

Solder balls | 17 July, 2008

To quote a regular here, "Are you sure your washer is set up correctly?" :P He's a WS junkie.

This is a really common problem and is discussed here often. Mid chip solder balls (solder beads) are almost always the result of too much paste being deposited during printing. Stencil design parameters (look at thickness, aperture size, and aperture shape) are the usual suspects.

Search "solder balls", "solder beads", and "mid chip solder balls" on SMTnet for some extended threads on this subject.

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#55585

Solder balls | 17 July, 2008

"Are you sure your washer is set up correctly?"

Now, that's funny!!!! ;P

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#55586

Solder balls | 17 July, 2008

Which type? * Solder beads (mid-chip solder balls, attached to the waste line of your chip caps and resistors) This is more paste volume related. * Solder balls that tend to be more randomly scattered (as in spattered)? This tends to be more profile and/or moisture related.

2 Solder Ball Causes & Corrective Action 2a SMT Process Related 2a1 Too much solder on pads * Decrease stencil thickness * Decrease aperture size 2b Equipment Process Related 2b1 Solder splash into pot rebounding onto board * Adjust anti-splash gates 2b2 Insufficient Activator * Increase conveyor speed * Increase flux activator/solids content * Increase quantity of flux applied * Reduce air-knife pressure 2b3 Vibratory device in 2nd wave set too high * Reduce energy level to vibrator 2c Material Related 2c1 Flux solids content too low * Correct specific gravity * Change flux 2c2 Solder mask not cured correctly * Check at Incoming and correct 2c3 Flux contaminated * Drain fluxer and refill with fresh flux 2c4 Solder mask not compatible with flux * Change solder mask or flux

Look here; * http://www.globalsmt.net/troubleshooter/wave_solder_ball.htm

* http://circuitsassembly.com/cms/content/view/3862/95/

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#55590

Solder balls | 18 July, 2008

Try using a homeplate design on your stencils. Works every time.

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#55595

Solder balls | 18 July, 2008

I think Real Chunks has your answer home plat or reverse home plate or like we use a 10% reduction on most aptures vs pad I think your problem is to much paste on the pads we used to see a lot of that with 8mil stencil thicknes on our 1206 caps went to 6 mil stencil 10% reduction fixed it for us

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#55596

Solder balls | 18 July, 2008

Thats it. 6 mils works great with a 10% reduction. We had also had some issues with our p&p placing the parts to hard and smashing out paste causing a bead to form in the middle of our 0805 packages.

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Bob Willis

#55702

Solder balls | 26 July, 2008

We have created a new online free database on process defects at NPL which you can search. http://defectsdatabase.npl.co.uk

There are many reasons for solder balling on wave and reflow and examples are provided. You could always use the database to post defects?

Many thanks

Bob Willis ASKbobwillis.com

This message was posted Add this forum to your site! Click to learn more. the Electronics Forum @

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#55711

Solder balls | 28 July, 2008

Your problem is being caused by to much paste being printed.Reduce apeture size on stencil. http://www.shanelo.co.za/technical_paper_about_stencil_de.htm or http://www.shanelo.co.za/SMD%20Assist.htm

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#55722

Solder balls | 28 July, 2008

Hello everyone,

thanks for the feedback. Now I am sure it is too much solder paste. It seems that the pads are a little bit bigger than they should be, so I will probably need an aperture reduction more than 10%.

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#55723

Solder balls | 28 July, 2008

Be careful of just reducing your aps. Too much can cause tombstoning if your print is slightly off or your placement isn't right on. Also be careful of the "pac-man" type of ap - it can lean to asty cuts if you wipe off your stencils by hand.

Do a simple homeplate and you'll see the differnce. Contact a new stencil house and you can get it cut for free. (sorry stencil guys)

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