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BGA Repair Medium

Views: 2864

Chunks

#43541

BGA Repair Medium | 24 August, 2006

Do most use tacky flux or stencil paste when doing BGA repair/replace?

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#43543

BGA Repair Medium | 24 August, 2006

Medium?? We prefer fully-baked. No, no. It's hearing messages from just about any dead component or board. "Wooo. Chunks. You dove me in the wave solder machine a year ago. I forgive you, because I never saw myself working in a karaoki bar."

There is no IPC requirement for reworking BGA either solder paste or just flux. While we generally use paste flux only, we believe the general consensus is that both methods work well. Adding solder paste, while more difficult, results in larger package standoff that should improve reliability.

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#43544

BGA Repair Medium | 24 August, 2006

We tend to screen paste to the BGA ball. This is quite effective although the repeatability of screening is not always great. Does anyone else use this method and how or have you managed to overcome this repeatability issue.

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RDR

#43545

BGA Repair Medium | 24 August, 2006

Paste flux exclusively, unless it is high temp ball Non reflowable), then paste is used.

Russ

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#43546

BGA Repair Medium | 24 August, 2006

we use a stencil and aply paste to the BGA have used sticky flux but prefer pasting the BGA

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Loco

#43547

BGA Repair Medium | 24 August, 2006

We use tacky flux, we just make sure the left over solder on the board is really flat, it kinda replaces paste, although there's probably less solder left then there would be paste.

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Chunks

#43550

BGA Repair Medium | 24 August, 2006

Now how did you know we were wave soldering BGAs onto a board that goes into a karaoke machine?

Thanks for everyone's input. We currently use tacky flux, but I beleieve we will also look into screening paste onto the BGA as well.

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#43557

BGA Repair Medium | 24 August, 2006

We know, we just know. The boards, they speak to us from the other side.

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RDR

#43576

BGA Repair Medium | 25 August, 2006

So why do you want to screen paste as well chunks?

Russ

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Chunks

#43583

BGA Repair Medium | 25 August, 2006

With tacky flux, the BGA is not as reliable as one that was never repaired. I believe Dave stated that the higher offset may have something to do with it. Also with tacky flux, the ball collapse form side to side varies a bit. Sometimes a ball(s) may not make contact at all.

These are government protos and the engineers I deal with are very stand-offish. They say they do "James Bond" kinda of stuff to test these boards so when one fails I'm not in the know of how or why. "If they tell me they have to kill me" kinda stuff. So I would like to provide the best repair process possible to assure I can limit my time with their egos.

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SWAG

#43588

BGA Repair Medium | 25 August, 2006

I've used those kapton, stick-on "stencils" a few times. Worked well for us. Toughest part is getting the kapton pattern in the correct place. Adding paste and placing the part is easy.

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CL

#43589

BGA Repair Medium | 25 August, 2006

We use "tacky flux" for most BGA replacements. We have found that we sometimes need a microstencil for paste on Micro BGA's.

CL

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RDR

#43591

BGA Repair Medium | 25 August, 2006

thanks

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Chunks

#43610

BGA Repair Medium | 28 August, 2006

Hi SWAG, Hi CL,

I've seen the BGA Kapton things, I believe we'll go in that direction as well.

I agree with you too CL. Depending on the product, I either have issues or no issues. That's why I was posting here, just to see if it was me (as I am always accused).

I got a lot of good ideas from everyone. Thanks to all.

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SWAG

#43614

BGA Repair Medium | 28 August, 2006

Yea, the kapton works good. We've had great success with some pretty fine pitch BGA's. Clean the site well, place the kapton stencil and make sure it's 100% adhered. Apply kapton tape around the perimeter of the stencil for ease of extra paste clean-up. Add paste and gently clean the surface until the apertures appear full and the kapton is clean. Remove the perimeter kapton. Place the BGA on the kapton say about 1 ball away from aligned and slowly move it in the direction of alignment and you'll feal it drop in. The kapton can stay under the BGA. Reflow it...

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bwet

#43634

BGA Repair Medium | 29 August, 2006

Ladies and Gents:

There have been several studies including (http://www.solder.net/PDFs/LeadFree_BGATesting_InitialCycling_BEST.pdf) which have shown lower fast pass yields with solder paste. Based on internal projects of 1000+ of the same BGAs we are able to dial in a 95% first yield with tacky flux only. With solder paste this yield approaches 99%+ (just BGA rework issues).

From a reliability standpoint one gets better results using solder paste printing (shake, vibe and thermal shock testing).

BWET

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