Old paste solder?

How important are reliability and traceability (ISO 9000) in your lab?

So can you tell me what happens to solder paste when it gets old?

No, that would be your problem.

Precisely -- I asked the question because I wanted to know the answer.

Can anyone tell me what happens, physically, to solder paste that gets old, and why it's no longer considered suitable for use? I know the specifications say not to use it.

More generally, if I didn't know whether some solder paste was fresh, what changes should I look for?

"mc" wrote in news:zqrDh.16146$z6.4928@bigfe9:

IIRC,old solder paste tends to form little balls instead of reflowing properly. Then you have them getting into the worst places and shorting things.

"mc" wrote in news:p2sDh.16179$z6.1559@bigfe9:

perhaps the flux degrades,absorbs O2(oxidizes),loses it's fluxing ability?? It may not be readily apparent from a visual inspection.

Thanks! Just the information I was looking for.

In article , snipped-for-privacy@www.ai.uga.edu.for.address (known to some as mc) scribed...

I'd like to know this myself, as I'm in the final stages of getting set up to do SMD work and I just spent $250 for supplies (solder paste, flux, wetting solution, tools, etc.)

Simply being told "How important is reliability and traceability?" doesn't cut it with me, any more than pointing to the expiration date on a tube of solder paste and saying "Never use this after this date!"

I want to know what, exactly, changes, and how it affects reliability (I don't give a flying poof-ball about traceability as long as the solder holds). I also want to know how these alleged changes will affect the stuff in terms of making simple repairs with (mostly) PLCC's and QFP's.

I'm not doing mil-spec production here... just trying to do decent repairs.

Keep the peace(es).

They'd like to sell you new stuff before you use up the old stuff. Try it and see what happens.

understand

Can you try accelerated aging tests. I remember there was a daily cycle of over-night freezing and (day ) low oven heating that closely resembled aging for paint, so 1 week accelerated, simulated about 1 year of normal conditions

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Why not just contact the solder paste manufacturer's technical department and ask them ? Most makers of service materials are happy to answer questions on their products. FWIW, I seem to recall the same as Jim, but it seems pretty clear that none of us on here *really* know, so we could be giving you a completely bum steer. If you do find out from the manufacturers, post back, and tell us all, as it would seem that there is at least one more in this thread who *needs* to know, and probably a few of us who would *like* to know.

Arfa

Well done you! There is so much bullshit around these days...ROHS..Health and Safety...WEE.. compliance this etc., the list goes on and on. The rules and regulations have gone mad in Europe, they are killing our industries. Stuff em all I say! Does it do the job? Yes? USE IT. If not DONT.

Meanwhile the Chinese do whatever they like and stick a sticker on that says they did what YOU wanted.

Well, then you go elsewhere to determine that (the manufacturer of the paste seems so dreadfully obvious). Or, you just try the stuff and see what results you obtain and see how many failures occur that haunt you later.

Geez ... this is a repair group. "What, exactly, changes, reliability" ... you are expecting too much.

Pardon me for asking a question in a newsgroup, then!

I got a remarkable cascade of "you shouldn't expect us to know" and only one helpful answer.

I assumed the people in a repair newsgroup would have experience using paste solder and might be able to tell me about their experiences with it. Or if they didn't, they wouldn't reply.

Now now, there's no need to get arsey. I think that you got a number of reasonable replies amongst them all, not the least of which being, from several of us, "ask the manufacturer". It's hardly rocket science is it ? Those of us who use the stuff in our everyday work don't let it get out of date, so we don't have any direct experience of what goes wrong with it. The guesses about the flux going bad or maybe the carrier, seem reasonable, but they are just that - guesses. Probably, nothing much happens. If you keep a packet of cornflakes past their 'sell by' or 'best by' date, without opening them, they will probably be ok a year later. If you have opened them, they won't be. Probably the same with the solder paste, but if you are going to be using it professionally, do you want to risk it ? Could cause you all sorts of problems down the line, so I say again, ask the manufacturer, then you will know for sure, and you can tell the rest of us. If you don't feel confident enough to talk to them by 'phone, I'm sure that they will have an e-mail that will reach their technical people ...

Arfa