Solder Joint Strength on Fine Pitch

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Our R&D Guys used to push the lead of a fine pitch component... - Aug 15, 2001 by

Ouch! I thought that went away 12 years ago! Visual insp... - Aug 16, 2001 by

Hussman is correct. Make those people quit. [Just walk-up, ... - Aug 16, 2001 by davef

hardy boy

#17231

Solder Joint Strength on Fine Pitch | 15 August, 2001

Our R&D Guys used to push the lead of a fine pitch component using a Pick or a thin metal tip and if the lead snapped off from the land it's considered failed. Is that the proper way of identifying the solder joint strength? We got problems with solderability before and was traced to insufficient solder paste deposit during printing. Now that we have a good soldering, but they are doing this test....most of our boards do not passed.

regards,

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Hussman

#17242

Solder Joint Strength on Fine Pitch | 16 August, 2001

Ouch!

I thought that went away 12 years ago! Visual inspection to IPC standards should be used. Pulling and pushing leads is not even close to being consistent. I bet your customers or ISO auditors have never seen this practice. If they must pull and push, have them use their weakest operator so you can get more products through! Not that I would want to buy any of it - pulling and pushing leads only weakens the solder joint by causing micro-cracks.

You can easily establish a medium using your own product too. Have one of your pieces sent out for vibration testing, physical and thermal shock etc... I'm sure your QC people can even help you determine what tests to do. Then do a visual inspection from there. If they must pull or push, at least use a force gage to keep them consistent to a known measure! Even after pulling or pushing with a force gage, I'd still scrap that product

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davef

#17250

Solder Joint Strength on Fine Pitch | 16 August, 2001

Hussman is correct. Make those people quit. [Just walk-up, pimp slap 'em, grab their dental pick, and say "Dave says you can't use this any more. I'm just following orders."][Trust me, this is much smoother than the "Tonya Harding Approach" that I espoused a year or so ago, here. Right Vicki?]

Hey wait a minute, are these the pathetic TQFP100 with the punky toe fillet that we spoke about the other day? Well I'll tellya, this is starting to piss me off. Tell those guys "NO JELLY DONUTS!!!! Sit!!!" [That always works with Officer Hardass when he pulls me over on the way back to the shop after a run to Krispy Kream. Well, that and him scoring half my haul. I steadfastly refuse to pick-up the cleaning bill to get the white stuff from his tie!!! By afternoon he's messed-up his spare and is workin' open collar. What a racket!!!]

Almost all solder connections to electrical components are for mechanical connection and electrical conductivity. A solder connection is not meant for mechanical strain only good electrical contact.

Applying force causes even a good connection to deteriorate. Even if the lead doesn't pull from the joint, the process affects the quality of the connection. If your inspector thinks of this as a non-destructive technique then, he is wrong. It is certainly deteriorating the solder joint(s).

How does the inspector know he hasn't applied 99% of the breaking force required and that the joint is only now hanging on by a whisper and a prayer?! [Got them calibrated elbows at inspector school, I'll bet.]

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