Relay - Doesn't work....at first

Question

I have a latching small signal <2A relay (V23079E1201B301) that switches between two audio signals. The relay has worked in about 10k boards over 7-8 years without much issue. We recently got a run done and 4 of 6 boards that we built the relay doesn't work at first - it passes audio in one position but not the other. But then after it switches on/off 15-25 times it starts working sometimes, and then after 30-40 switches back and forth it passes signal fine. If I power it off and check it a few hours later it's still fine.

I hear it clicking every time so I don't feel like it's sticking. It's almost like there's oxidation on one set of contacts and it eventually burns off. I'm a little nervous because I haven't experienced it before, and not sure if there's going to be long term reliability ramifications. I ran the issue by our repair guy and he says the relay never an issue with units coming back from the field.

Anyone else experienced this?

UPDATE: I broke apart a good relay (date code 2014), and one of the recent ones that had been 'exercised' a bit and now conducts (date code 2019). Comparing them they're super similar. A few differences, but nothing that screams counterfeit.

The obvious issue though is that I can see black stuff on one set of contacts (the moving contacts). It's worn off and gold again in the middle, likely from the exercise, but you can see black bands along the outside. Interestingly there doesn't seem to be any other decay or oxidation on any other part internally - or the stationary contacts. Maybe this suggests that it didn't become un-sealed, but that the moving arm has a defect with the finish. I'm not sure.

Going back and forth with the CM and manufacturer to try to get to the bottom of it. Thanks for all the advice.

Answer 1

Make sure the relays are not counterfeit. I assume you've specified gold-plated contacts. Might be worth dissecting one from current production, though it would be difficult to test if the plating (assuming there is some) was thick enough.

But my fancy ratio tran$$$former box "exercises" the relays upon each power-up, so they are expecting trouble.

Generally gold-plated contacts are okay if you pass more than a few uA (10uA, say) "wetting current".

Answer 2

Have you changed your manufacturing process by any chance? It is possible for flux or cleaning solution to make its way inside of relays during reflow and cleaning. Even if the relays are sealed, there are still specifications to watch out for, especially in lead-free processes.

If disassembling the relays and/or having a professional lab evaluate the contacts for contamination, watch for traces of organic elements.

Go to the product webpage on TE's website and take a look at the "Transportation, Storage, Handling, Assembly and Testing" datasheet (sections J through O) to see if you are within their specs yet.

Anecdotally: I spent months chasing down a very similar issue with what might have been the exact same model of relay. TE disassembled a few they had reserved from the same lot code at their Czech plant and found no issue. A third-party lab cracked open some relays from before and after the manufacturing process and found organic contamination on the contacts of the parts we pulled off manufactured boards. Finally, our contract manufacturer admitted to using a solder process that was hotter than they were supposed to use, then were spray washing them with liquid that was definitely too hot and high pressure. We believe when the relay cooled, it may have sucked residue in through the micro-cracks in the relay seal from the too-hot reflow.

Answer 3

Different batch of relays?

If from a reputable supplier, contact the supplier (and if you have more, set aside a couple that fail WITHOUT exercising them, as samples to send back).

The worry is that having cleared them, a period of idleness (and cold, or warm, or humidity) will restart the problem once these are in the field.

Answer 4

Check:

1. Has the testing setup changed?

2. Your source of supply. Are the parts genuine?

3. When were they manufactured?

4. Have you complied with the manufacturers storage and design instructions in the datasheet etc.

5. Check that your soldering process or any other relevant manufacturing process hasn't changed

6. Provide the findings to vendor and manufacturer and request RMA