Manufacturing defect in solder joint, likely cause?  - Page 1
Forum section: electronics / projects

author: turbo!
author_rank: Regular Contributor
timestamp: December 26, 2013, 04:30:21 am
content: I have this Acculab scale, which then cost $300-400 and was considered a bargain back in the late 1990s. Acculab was a manufacturer of laboratory scale until it was acquired by Sartorius AG and eventually eliminated.I got it used and it started having issues with complaining of overload at half load. The display sometimes got jumpy and was responsive to shock on the case. I cut off the connector to load cell and soldered it in since that was the only mechanical junction on analog side. I thought it fixed it for a while, but I just started having issues again. It sometimes went away after it was warmed up. "Made in the USA" and all. I didn't expect faulty solder joints.Anyways, it is finally fixed completely and it was a defective solder joint. I simply re-worked the faulty joint with 63/37 lead solder. The white powdery residues was already on there. The issue was inadequate solder fill on precision resistor used as a voltage divider on analog side. The unit was made sometime in 1999. What causes this kind of soldering fault? Was this around the time they were making lead free transition?What I did a few years ago.The real cause of fault. Lower right.

author: Rerouter
author_rank: Super Contributor
timestamp: December 26, 2013, 04:36:20 am
content: its very much on par with what i see in American automotive instrument clusters of that time period,just barely skirting enough material like it was some kind of bean counters pet projectthough to be fair the same happened with a large number of japanese cars around 1995-1997

author: ignator
author_rank: Regular Contributor
timestamp: December 26, 2013, 04:59:43 am
content: I watched similar quality of avionics assembly occur in this time period. It has to do with getting rid of inspectors.i.e. save money. So the assembly operator does their own inspection. And because you can't hire skilled operators to do this work, you get this sort of quality. The unit worked and passed test, so it was shipped. There was no secondary inspection because it worked, as factory test repair only looks at units that fail test.

author: turbo!
author_rank: Regular Contributor
timestamp: December 26, 2013, 05:26:02 am
content: Quote from: ignator on December 26, 2013, 04:59:43 amSeems like Made in the USA is just a euphemism for we don't turn enough volume for Chinese manufacturer to consider it eh?

author: SeanB
author_rank: Super Contributor
timestamp: December 26, 2013, 06:21:19 am
content: I can understand how that was done. A select on test resistor or a resistor supplied matched to the load cell, and the assembler had already a board fitted into the case, so just cut the leads, dropped it into the holes and blobbed solder on the top. Top jint was dry as the ground plane sucked all the teat away ,but it had just enough metal to metal alloyed contact to survive around 1000 cycles of day/night cycling before it work hardened and fatigued to fracture. Then it depended on vibration to make it temporarily, like when the plug was removed.

author: Richard Head
author_rank: Frequent Contributor
timestamp: January 08, 2014, 12:37:14 pm
content: Spot on SB. If the guy had left the iron on for another second or two the solder probably would have wicked through the THP to the other side and we would be having this conversation.Rich