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Flux residue cause high false reject at ICT

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#45743

Flux residue cause high false reject at ICT | 29 November, 2006

Dear All,

I have 1 product that using solder bar from vendor called Asahi. After wave process, we found quite a sticky flux residue remain on the board. Eventually, have huge impact on our ICT fisrt pass yield(FPY). Current FPY is a the range of 80 to 85% only..Yield lost due to 20% to 15% false call.

Do you have any idea to reduce this flux residue during wave process(Lead free)?

Thanks for your time...

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RDR

#45750

Flux residue cause high false reject at ICT | 29 November, 2006

So why are you telling us about the solder bar? What is the flux? that is what you need to change, you have a rosin based flux it sounds like.

you can change probes in test fixtures or change flux chemistries.

Russ

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#45751

Flux residue cause high false reject at ICT | 29 November, 2006

Washing these boards would be a great help.

The flux will build up on the probes and possibly corrode them depending on it's composition. Aim for a process that will burn off the majority of the flux, or change chemistries if washing is not an option.

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CK the Flip

#45758

Flux residue cause high false reject at ICT | 29 November, 2006

For the better part of my career, I've battled with ICT guys on so-called "flux residues" on their test probes, and this was when using NO-CLEAN, 2% to 5% solids tops, flux.

People don't understand that ICT probe maintenance is an inherent part of being a "no-clean" shop. Jeez...how long has no-clean been around anyway?

Now, if you're using a wave flux which you do have to clean (rosin-based, RMA's, or water soluble/OA), yes...you have to water wash your assemblies or they'll corrode your ICT probes.

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greg york

#45832

Flux residue cause high false reject at ICT | 30 November, 2006

This may be worth checking out are you sure it is flux residue and not undercured plasicizers coming from solder resists due to the higher Lead Free temperatures killing the undercured resist, this causes many no faults found and bridging, solderballs, snail trails of solder stuck to resist. Ususally seen by a brown liquid gum in the solder wave were the solder falls back into the pot on the metal former. Worth a check, seen it 'LOTS' over here with good old Lead Free processes. Cheers Greg

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#46049

Flux residue cause high false reject at ICT | 7 December, 2006

Hi all,

Sorry for the late reply..I am sure it is flux residue..Found no such symptom as Grey mention above. This is non clean process and no way we can clean this whole big board(Server) with any kind of flux removal...Currently, the ICT probe preventive maintenance is at every 80K hits. I checked with my friends, and they told me 80K hits is too late..They advice me to reduce to 20K or 30K hits. They said, lead free non clean flux is much harder to be removed and hence a frequent probe maintnence is necessary. What do you guys think about this proposal??

Note: We do have daily brushing the ICT probe & sampling check on the probe condition besides the above mention activitiy..However, see not much improvement..

Cheers

Thanks..

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Rob

#46091

Flux residue cause high false reject at ICT | 8 December, 2006

Try flux buster ICT pins.

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#46092

Flux residue cause high false reject at ICT | 8 December, 2006

Depending on the system you can program in a loop where if the board fails a contact to cycle the vacuum once or twice. it wears on the pins a little faster since you cycle 2 times (maybe more) per board but it could help increase the FPY. I know Genrad systems can be programmed to do this fairly easy, not to sure on the others.

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Loco

#46223

Flux residue cause high false reject at ICT | 18 December, 2006

Greg, Is there another way to check for those uncured plasticizers? How are they normally cured? If you could cure them yourself, I guess a difference would be noticable.

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greg york

#46225

Flux residue cause high false reject at ICT | 18 December, 2006

Good solvent wipe will normally show some discoloration of the same colour as resist, but not scientific enough as you cant gauge the amount coming off, ideally none. But is an indicator of the issue. I have been meaning to do a swab with an indicator in it for years but never got round to it so far. Recuring can help as long as it is at the correct temp no point curing again at 140c when it MUST be 155C will not do a thing, but yes it does solve the problem. Cheers Greg

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Loco

#46227

Flux residue cause high false reject at ICT | 18 December, 2006

Thanks, if you ever get round to producing those swabs, you can put me on the order list.

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laxminarayana pai

#46290

Flux residue cause high false reject at ICT | 19 December, 2006

Well, you need to change your solder paste.There are pastes available in the market which are meant for ICT pin testability.

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greg york

#46292

Flux residue cause high false reject at ICT | 20 December, 2006

Consider it done Cheers Greg

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sjlevin@ix.netcom.com

#46316

Flux residue cause high false reject at ICT | 20 December, 2006

We use a solvent called AK-225ATE (there is also AK-225T) that works great for removing RMA flux residue and no-clean flux residue. Info at http://www.AK-225.com

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