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Solder balls on Cleaned process

Yngwie

#17937

Solder balls on Cleaned process | 17 October, 2001

We are running Clean process. solder beadings were found after the wash process. Weird eh!! It's true.. Details:

1)wash pressure ? No shadowing effects from high profile component. It also happened on the component's body of the 1210 & 0402 caps which located at an open area. 2)Open time is too long i.e. time from printing to reflow, if so, what is the best timing I should consider here. We are currently at 15 minutes. 3) Wash temperature, currently we are at 55 deg C - 60 deg. is it OK? 4) Reflowed board were left too long prior wash, since it is double sided i.e. instrusive reflow. We processed Secondary side first before the primary side. And the solder ball were only found on the secondary side. 5) Even if the solder aperture is the culprit, it should be washed-off isn't it? 6) Time above reflow is 60-70 secs. I assumed this is fine. afterall if sodler ball do exist it should be washed off.

What could possibly be wrong from your guys opinion ?

Help is really needed here. Pls respond and thank you in advance.

/Yngwie

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#17939

Solder balls on Cleaned process | 17 October, 2001

2) Open time: A 15-minute queue between paste, place, and reflow SB fine, assuming humidity is not too great. 3) Wash temperature: Yes. A wash temperature of 130-140�F SB fine. 4) Reflowed board was left too long prior wash: Are you washing: * After reflowing the secondary side AND after reflowing the primary side? * After reflowing the primary side ONLY? 5) Solder balls should be washed-off: Yes they SB washed-off, assuming your washer is working, the balls are not imbedded in the solder mask, and boards are washed within a reasonable time after reflow. 6) Time above reflow 60-70 seconds above liquidous SB fine.

If a solder ball exists, it should be washed off. Right!!! That's why we love to see nc flux people whining about solder balls!!! It is so funny!!!! ;-)

My opinion: * Boards were not washed after the first reflow [of the secondary side]. * Flux residue from that reflow turned to a semi-cured concrete and entombed the solder balls loitering around, while awaiting further processing. * Second reflow [of the primary side] fully cured the flux residue from the first reflow. * Aqueous wash after the second reflow did a wonderful job of cleaning the residue and solder balls from the primary side processing, but bounced-off of the solidified residues from the first reflow, like a dog merrily chasing an outside squirrel from in-side the house, but not realizing the sliding glass door is closed. Oooo!!!

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ScottM

#17944

Solder balls on Cleaned process | 17 October, 2001

Dave's right! Wash the boards RIGHT AFTER reflow, don't let that residue harden.

Then you turn around and cure that stuff during the second reflow by not performing the first wash???? wow....

By the way, are you having any problems with white residue?

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Michael Parker

#17945

Solder balls on Cleaned process | 17 October, 2001

Duh?? white residue??? could be the source of anthrax

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Yngwie

#17948

Solder balls on Cleaned process | 18 October, 2001

Dave, yes, your assumption is right, We only do washing after the second reflow. The timing from the post primary reflow to wash is no longer than 2 hour. The line config is as such :

DEK265 � 3x MV2F- 1x MSF � BTU - AOI � DEK265 � 3x MV2F � 1x MSF- BTU- AOI - WASH - mech assy-test bla-bla-QA bla bla-packing bla bla

It�s too bloody long�.( don�t ask me why�I jointed the company acuppla mths back..and it�s already like that )�.and I think If I were to add another wash at Post primary reflow �it�s gonna make a history in world Guiness Book of Record.

To answer the question from Scott, no I didn�t see any white residue.

Thanx for your help guys!!!

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#17949

Solder balls on Cleaned process | 18 October, 2001

Ooooo, you do have the toys, baybeee!!!!

This really is not a good situation. * Leaving this OA flux res on your boards will surely affect the LT performance of your product. * That a rookie found this by noticing solder balls all over the secondary side of the board indicates that you are not controlling you wash process well. [Although, I might be opening my BIG mouth too early on this one. Ya know, I�m not sure how well reflowed water washable flux res shows-up in a solvent extract test. Would you run a couple of boards out of the washer and tell me the answer? Maybe running a bare board as a baseline.]

Don�t kid yourself. It�s not a matter of �too bloody long� time. It issue is cooked flux res.

The good news: Solder balls are probably acceptable, because there entombed in the cooked flux res. ;-)

If what you describe is the routine, you should consider changing to a: * NC flux, selling your washer for BIG bucks, and taking everyone to lunch with the proceeds of the washer sale. * New flux supplier. Recently, a sales type pitched us on a washable flux that reported doesn�t have to be cleaned between reflow cycles.

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