Solder "wicking" up THT connector - Page 1
Forum section: electronics / general

author: kylehunter
author_rank: Regular Contributor
timestamp: December 18, 2020, 02:26:49 pm
content: Hey all,Just had a first. A client rejected some recent boards we assembled. The reasoning is that the male mating pins of a connector couldn't fully mate with our female rectangular one. They said the solder wicked from the bottom of the pins, upwards and clogged the contact portion. We solder these connectors with a selective soldering machine.This seems incredibly odd, and frankly, doesn't seem likely to me. Our selective drag solders these pins pretty quickly, so I don't really see how this is possible unless some manufacturing defect left an opening for the solder to wick up. I'm more so expecting to see the inner contact portion bent.Anyone heard of this or have any input? I checked through IPC-610, and couldn't find anything. We'll get the boards back to inspect, and will report back.Oh, the connectors are the SSW series by Samtec.

author: phil from seattle
author_rank: Super Contributor
timestamp: December 18, 2020, 03:53:26 pm
content: Did you pull one of the boards and dissect it? Looking at that connector type, solder would have to wick up into the plastic body fairly far. Seems like a more likely failure is plastic distorting from heat.

author: kylehunter
author_rank: Regular Contributor
timestamp: December 18, 2020, 05:20:15 pm
content: Quote from: phil from seattle on December 18, 2020, 03:53:26 pmNot yet. The client is shipping them back. Yeah, I agree with your thoughts about how far it would have to wick up. I'm betting on either what you said, or the contacts within got bent somehow.Though we did test this part for pin in paste a while back (decided against it), and it withstood that heat without failure, so I doubt it's that either.

author: Mangozac
author_rank: Frequent Contributor
timestamp: December 18, 2020, 11:01:34 pm
content: Why did you decide against pin in paste? It's something I would really like to pursue at some point.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: December 20, 2020, 03:57:48 am
content: Did the client provide you with a stencil that has holes to paste the pins of these connectors? After all, these are THR connectors and must be sealed with paste in the reflow. They should not melt and suffer from temperature. And I can quite admit that solder leaks deep are likely with selective soldering.

author: kylehunter
author_rank: Regular Contributor
timestamp: December 21, 2020, 01:40:33 pm
content: Quote from: S. Petrukhin on December 20, 2020, 03:57:48 amHuh? We didn't do it with pin in paste, we used a selective. "After all, these are THR connectors and must be sealed with paste in the reflow." What?

author: S. Petrukhin
author_rank: Super Contributor
timestamp: December 21, 2020, 01:44:48 pm
content: Quote from: kylehunter on December 21, 2020, 01:40:33 pmIn appearance (there is a distancing of the case from the surface of the board), I think these are THR connectors designed for paste.

author: kylehunter
author_rank: Regular Contributor
timestamp: December 21, 2020, 01:49:34 pm
content: Quote from: S. Petrukhin on December 21, 2020, 01:44:48 pmAh. Well, there's not a single mention of pin in paste on their webpage or the datasheet about it. If they were unable to be used as THT are traditionally used, I would certainly hope they would at least make a casual reference to that.

author: thm_w
author_rank: Super Contributor
timestamp: December 22, 2020, 10:48:55 pm
content: It says in thesheet:Lead–Free Solderable: Yes: -S and -D row optionWaveonly: -P, -T and -Q row optionNormally you'd expected the pins should be sealed at the base to the plastic housing. I have some in front of me and there is a tiny gap (~0.2mm) between the side of the pin and housing. But even trying to force solder in there does nothing.