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SMT electronics assembly manufacturing forum.


Old relay oxidized

#18341

Old relay oxidized | 5 December, 2001

What is the best way/material to clean leads with 20% copper exposed that have been sitting in a stock room for a couple of years. My process uses NC flux 263 from AIM and I want to stay with the NO-Clean as much as possible!

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#18346

Old relay oxidized | 5 December, 2001

Now there�s a conundrum. You want the �best way to clean leads�, but you want to use the worst type of flux for cleaning leads.

You say, �20% copper exposed� � * What happened to the solderability protection during this two-year storage? Wouldn�t the copper at least remain covered with solder, even if it didn�t solder well? * What is the level of coverage when you solder these components?

Hard to say based on the information you�ve provided. First and foremost get an account number for charging labor and materials to the mutt that bought-in the relays a couple of years early. Thoughts are: * Determine if your current AIM 263 NC flux will do the job. * Talk to your flux supplier to get a recommendation on a more active NC flux. * At one time, Cal recommended using ROSA to reclaim the effectiveness of HASL board solderability protection. Contact the folk at EMPF [search the fine SMTnet archives for contacts] to determine if this can be used on your relays. * If the relay case is closed, use an aqueous flux to tin the leads, clean them, and then use your standard NC processing. * Send the relays back to your supplier, pay a �restocking� charge, and buy new parts. * Use a contract lead tinner, like: XL Addenda 708.971.8843 fax8846 Gene Binkowski Six Sigma 1940 Concourse Dr San Jose, CA 95131 (408) 526-1350 Fax (408) 943-0447 sales@solderquik.com

Corfin Industries 7B Raymond Ave, Unit 7 Salem, NH 03079 603-893-9900 fax 6800 http://www.corfin.net admin@corfin.net Thomas Hamel Chip Pro 10390 E. Lakeview Dr #206 Scottsdale, AZ 85258 480-860-5790 Fax 8366 Processing Facility 1610 No. Freeway 35E #214 Carrollton, TX 75006 972-242-9455 fax 8497 http://www.chipro.com

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smtspecialist

#18359

Old relay oxidized | 6 December, 2001

Thanks for the info,

Of course the first thing to do was to look with my supplier, but the problem was that it's a special relay, custom made from a design created 10 years ago. Two years ago that company went BK and we had to order a whole bunch to cover for our future orders. In the process, I guess the supplier had to cut the leads in order to meet the specific width, then they didn't retinned and here at incoming receiving they accepted it. That was before my time, things are not done the same way any more!!

So I had no choice but to deal with the rest of the 800 relays left in stock here in order to meet my production schedule until board is re-designed (which is ongoing).

To get the good results I was looking for I had to use Organic flux on the relays then wash it and then sent the relays back through my regular process which is NC.

I did a 100% inspection after re-tinning/regular process and out of 200 boards/parts, I got only 4 that was still not soldered properly.

For the 800 relays left in stock I am currently trying Liquid Tin, have you ever tried or see that?

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#18363

Old relay oxidized | 6 December, 2001

No.

Assuming your talking the MG Chemicals product, MG Chemicals makes innovative products and is a very innovative company.

Let us know how it works, please.

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smtspecialist

#18369

Old relay oxidized | 7 December, 2001

Yes it's a product from SG Chemicals, it does tin the leads but they stay doll, they don't come nice and shinny. So that tells me it doesn't clean off the oxidation it just add a tin coat to the lead itself, short term results are great but what about long term? I don't think I will use this methode for the 800parts left in my stock, I need to further investigate the long term issues first.

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#18378

Old relay oxidized | 7 December, 2001

Dull / shiny, I�m not sure that�s a proper indicator. If �Liquid Tin� adds a thin coat of solderable material without converting the corrosion on the surface of the lead, the corrosion will [probably] continue to increase and potentially affecting the LT reliability of your product, because a weakening bond between the coating and the lead over time. Some of similar products are conductive epoxies that coat the leads. The MSDS from MG Chemicals makes me think that their product is not an epoxy.

Determine the answer to your question by: * Micro-sectioning a lead of the relay and evaluating the bonding of this coating. * Taking to applications types at MG Chemicals.

Soldering the leads is probably the correct way to go, as you say.

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Michael Parker

#18400

Old relay oxidized | 11 December, 2001

What is the composition of tin to lead in the "Liquid Tinner"?

It's been my experience that the higher the tin, the duller the solder appears. I've used 63/37 and 70/30 that both look shiny, whereas 80/20 does look dull. Just another thought to consider.

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smtspecialist

#18416

Old relay oxidized | 12 December, 2001

I have observed the same thing with solder composition in this case I am using 63/37 NC which is giving good results usualy. The liquid tin, product from MG Chemical that I used is to tinplates copper circuit on PC boards.

I tried on few relays, it works but does it clean the oxidation? I don't think so! The MG Liquid tin contents is: Flouboric Acid, Stannous Fluoroborate and Thiourea. This is what I don't know does any of those chemicals remove/clean the oxydation or it just get mixed with it?

My best result are with Organic Flux to re-tin all relays then wash it. (It's more labor but at least I'm positive that the oxidation is gone!!)

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