Soldering issues lately!!

Interesting observation Manuel.

I will be blamed again for crying wolf but look below a lot more defects will soon see the daylight all related to lead-free.

This information was posted at the tin whisker forum by Bob Landman of H&L Instruments.

http://www.calce.umd.edu/tin-whiskers/whiskersusb.htm

What's Inside Your PC?

CALCE has recently discovered tin whisker on USB housings on a computer motherboard and USB housings in computer monitors. USB ports are very common in computers and peripheral equipment. USB ports provide easy connections and interfaces devices such as external hard drives, flash drives, printers, and cameras. In examining computer systems produced 2003 time frame (earlier for the motherboard), CALCE has observed very long whiskers. In a set of flat panel monitors, a CALCE Research Associate documented a 900 micron tin whisker.

Tin whiskers have been linked to a variety of field failures. Tin whisker are known to form on tin finished metal surfaces. Alloying lead (Pb) with tin is know to suppress the formation of tin whiskers. Due to European government regulations and market pressures, lead (Pb) can no longer be used in the majority of electronics. As a result of the lead ban, the use of pure tin finish has increased. While test standards have been established to assess tin whisker propensity, no accepted acceleration model for whisker growth based on the standard tests has been established. As a result, these tests cannot be used to predict the growth of whisker in the field or the probability of field failures associated with whiskers.

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Supporting documents can be found here:

http://www.calce.umd.edu/tin-whiskers/presentations/WhiskersOnUSB1-20080905.pdf

http://www.calce.umd.edu/tin-whiskers/presentations/WhiskersOnUSB2-20080905.pdf

http://www.calce.umd.edu/tin-whiskers/TINWHISKERFAILURES.pdf

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At first glance you would think so. But just as in real life manufacturing, EVERY problem can be solder related. Naturally the problems with broken parts, wrong parts, parts made wrong etc... are generally found right ways, so no one really posts those here. So like most managers' scream - every problem is a solder problem. But now dig down deep a little and most times you find it's every thing except the solder. The poor solder is just an innocent by stander!

Most problems I see are part related, board related or machine related. Most of my process problems are board problems because we buy from China. Not that I blame China for being the devil, but it can be hard to find a good reputable board house that makes a quality part. Right now one of my boards can be built by any of the seven manufacturing plants my board house reps. 3 of these plants are very scary to be in because there is no quality control. It shows on our boards all the time. Delaminating, broken traces, vias not drilled correctly.... I could go on for ever. Most times we see the problem and floor reject them right back to the manufacturer. They generally just eat it cause they know they have no leg to stand on. We have our fair share of bad parts too, but we have learned to try and get a little better at In Coming and can catch most of them. Boards are a little harder as you can't simply take a single measurement to test em good.

Brokered parts now are a different story. I once got QFP 180s in that had dried solder paste on the legs. They were tape and reeled and looked new until the placement machine had a very high fallout and the solder quality fell thru the floor. But once a again it was called a "solder problem" until we got the directors out of their offices and showed them (yes they still fit through the door).

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Its you

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