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ICT Fixtures No-Clean Flux

Cartman

#4647

ICT Fixtures No-Clean Flux | 16 March, 2000

Greetings.

My company has a VOC-Free no-clean wave solder flux with 4% solids. I have a number of questions as they relate to our ICT Fixtures. Currently, we're encountering the following issues:

1.) PM on probes....What is the recommended PM program on ICT fixtures...5000 cycles? 7000 cycles? INCREASED PM on ICT probes is a sacrifice that needs to be made with a no-clean process, right? ..because over time, flux residues DO build up on ICT fixtures.

2.) Are fixture contact problems an INEVITABLE part of having a no-clean process? Will SOME residue be left on the board- and yes, we're assuming a controlled spray-fluxing process. 500 - 1000 micro-grams per square inch flux deposition....Does Solder mask, and their different surface tension characteristics have a great effect on how much visual residue remains on the board, and does this visual "film" have an effect on ICT probe-ability?

3.) I've heard of fixture contact problems getting resolved AFTER a board is cleaned with an alcohol wipe. Have others who have NO-CLEAN processes encountered similar issues where they clean the "filmy residue" off or burn it off with a soldering iron, and THEN, it passes ICT???

Input from you folks would be greatly appreciated...thanks.

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#4648

Re: ICT Fixtures No-Clean Flux | 18 March, 2000

Cartman: Ah, another "hidden cost" of no-clean. I love no-clean people they're putting themselves out-of-business and they don't even realize it, but at least they're saving money.

Enough pontificating, "yes" to all of the above.

1 Yes, no-cleans gum-up ICT probes, some less than others. The typical NC is frankly "gummy." Other NC are more brittle and fracture with probe contact. Check your supplier. Also consider changing your probes (changing-out probes, now that's an attractive proposition, what are they $5 a pop?) in the future to a style that is more no-clean friendly. Check your supplier.

2 You're correct, NC residues are a function of the flux and the amount you put on the board. Some solder masks are more pourous than others and could affect the amount of reside on the board, but we're not talking ICT here, right? We're talkin' cosmetics.

3 Yes NC flux residues are a problem for test people.

Good luck and happy testing

Dave F

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#4649

Re: ICT Fixtures No-Clean Flux | 23 March, 2000

Hey Cartman: Recently, I was over at a plant that does ICT on RMA fluxed boards and asked them about flux residue on test probes. The test machine operators: * Think flux residues are a pain in the gluteus maximus. * Change probes (from a collection of different tip types: crown, straight point, diamond) to hopefully select (tailor) the correct probe for the probe location. How they keep track of probe changes ... I dunno * Dry scrub probe tips with a wire brush (a little like Techni-Tool 872M1034, but with longer rows of bristles) when a fixture begins to act-up. * Inspect the probe side surfaces for corrosion from the flux that prevents good contact. They change probes haphazardly. The probe manufacturer recommends a change-out schedule ... 50k hits or something like that.

Sounded like constant maintenance, maintenance, maintenance ... ooooo babeeee, if maintenance wasn't tough enough to start with ...

Good luck Dave F

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