Moisture damage to components - Page 1
Forum section: electronics / projects

author: jitter
author_rank: Frequent Contributor
timestamp: September 05, 2015, 09:33:43 am
content: Hoping someone with experience can help out...While testing a new batch of products, I found that a remarkable amount of miniature relays had failed. I have suspicions that these were not stored properly, but no proof.These are specified as moisture sensitive, level 3, meaning the package can only be left unsealed for a limited amount of time before the soldering process must take place.The symptoms are no or intermittent contact on NO and NC contacts. I've yet to look at them under the microscope.If moisture damage has occurred, what are the things to look for without cutting them open?Any insight appreciated!

author: matseng
author_rank: Frequent Contributor
timestamp: September 05, 2015, 09:40:27 am
content: I think that the moisture sensitivity rating has more to do with the solderability rather than functionability. It's quite common that smd parts that has been exposed to too humid conditions for too long time have to be "baked" to dry them up again before soldering.If the contacts *inside* the relay would be affected to outside humidity then that would also occur after soldering - unless the soldering process magically seals up the encapsulation 100%. Sounds not very plausible to me.... ^_^

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: September 05, 2015, 10:09:59 am
content: I think in the case of an electromechanical situation, the parts may have a coating or plating which will either tarnish or corrode with exposure to air/moisture. A forensic examination is due on your relay. aka "take it apart"Do you have a part number or picture at least to help?As far as an IC or other electronic part with an encapsulation, it can explode or rupture internally if soldered due to moisture inside the IC. Hence the necessity of baking to dry it out. Of course it may work fine but still fail before its time. Same situation with ESD.

author: jitter
author_rank: Frequent Contributor
timestamp: September 05, 2015, 10:21:56 am
content: Quote from: matseng on September 05, 2015, 09:40:27 amThanks for your reply.Next week I'll certainly be looking at the leads under the Mantis microscope. If solderability was the issue, then that should show up on the leads.However, visual checks of the non-functioning boards did not show up anything out of the ordinary, there was no obvious non-wetting.The reason why I suspect moisture damage is because I found a reel in the storage location that was sitting there all exposed. Unfortunately, none of the components coming from this particular reel had failed. I did see this lotcode on the batch but all failed relays were from another lot. The reel with the failed lot had been used up completely, so no way for me to know how it was stored.Yes, baking. We tried baking the exposed reel with hilarious results, the reel did not withstand 125 degrees C and crumpled. Why did the manufacturer use a non heat resistant reel? Well, max. ambient temp for the relay is specced at +85 degrees C. Oops, baking should have taken place at a lower temp...About 500 relays are now landfill...

author: helius
author_rank: Super Contributor
timestamp: September 05, 2015, 10:30:33 am
content: When the term "baking" is applied to components the idea is to slowly drive off moisture. You'll recall that the boiling point of water, where it all turns to steam and expands with great force, is 100 degrees C.Heating any moist component to 125 C is guaranteed to damage it, not to save it. That doesn't even require looking at a datasheet.Maybe we should change the term "baking" to "sous vide"

author: jitter
author_rank: Frequent Contributor
timestamp: September 05, 2015, 10:32:44 am
content: Quote from: Quarlo Klobrigney on September 05, 2015, 10:09:59 amNot yet, coming next week. Finishing the products on time was priority no. 1. Next week I'll have the task to explain why I took longer than usual to test the batch and may have to report that we caused the problems ourselves. This will not be accepted easily, hence why I want proof.I'm reluctant to share the part no. right now. I will wait until what's decided by the quality department. The manufacturer of the relay is a global giant and I did notice that the lot wit high failure rate was made in China while the lot with the improperly stored reel (but without adverse effects) were made in Portugal.QuoteFR4 pcb material is also very sensitive. Blow holes will occur during the soldering process if these are too moist. With hand soldering you can see bubbles coming from your joint when you have the iron on it...blub blub blub...

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: September 05, 2015, 10:34:14 am
content: Chance at a part number?BTW, baking can take place at a much lower temperature, even in the home oven at 125°F

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: September 05, 2015, 10:40:35 am
content: Quote from: jitter on September 05, 2015, 10:32:44 amWell Yaaaa,

author: jitter
author_rank: Frequent Contributor
timestamp: September 05, 2015, 10:41:26 am
content: Quote from: helius on September 05, 2015, 10:30:33 amApparently some JDEC standard was followed. Normally used on ICs and PCBs without any problems. I also believe that the baking oven ramps up the temp slowly. It was just that the plastic reel didn't withstand the temp. Given the low max. spec of the relay I decided to have them scrapped.Normally, we seal openend moisture sensitive devices (MSD) in the moisture barrier bags they came in with dessicant if they were only exposed for a short time. Otherwise they will be stored in a special dry cabinet (< 5% rel. humidity at room temp).

author: SeanB
author_rank: Super Contributor
timestamp: September 05, 2015, 01:18:51 pm
content: Chances are the reel that came from PRC could be a reel that was rejected for some reason, or is a "second source" ( also known as fake) part. Relays that fail contact wise would indicate contamination of the contacts, and if you open them and see the inner works are corroded or tarnished then they have been exposed to a corrosive atmosphere. As they typically are sealed for small units ( either a tape tab you remove or a small pip on top that you break off) moisture really has no effect on them, unless they actually got wet in an open package. Corroded internals is indicative of poor selection of components in manufacture or improper manufacture.The reel crumbling is expected, the plastic used is a glass filled styrene, something designed for cheapness and ease of recycling or throwing away after use. The plastic used melts at 70C or so, so it is easy to mould as it takes less energy.

author: jitter
author_rank: Frequent Contributor
timestamp: September 05, 2015, 01:44:15 pm
content: Quote from: SeanB on September 05, 2015, 01:18:51 pmThe one thing I'm sure of is that we don't do "second sources" unless there's absolutely no alternative. So they will be from an authorized dealer (Arrow, Avnet and the likes). No doubt the origins of this batch will be confirmed once I inform the quality department of the problems. The company I work for does lot-tracking as a matter of course for every component used.We were duped in the past with counterfeits of expensive parts like the TI/BB OPA627, and it's not funny when you have to take apart 100 or so products that are already assembled in a tight housing with soldered on wires (no connectors).In stock we have a factory sealed reel of the same relays, same country of origin (China), same datecode, lotcode differs only one digit. I'm going to keep a close look on how these will turn out. They are already allocated to a new production batch.QuoteWe did experience this fault on another batch of relays of a different type (same manuf. though), this time from the Czech Republic. But it was proven that our soldering process caused the sealing compound around the leads to crack. In the washing process that followed, this would allow water in which led to the inevitable corrosion. I openend these up and there was blue liquid inside. This was analyzed by the manufacturer and the liquid turned out to be water, detergents and corrosion products.

author: SeanB
author_rank: Super Contributor
timestamp: September 05, 2015, 02:07:46 pm
content: Then you might consider either doing a selective wash of the board avoiding the relays or simply use covers over the relay placed before the wash cycle. Otherwise you will have to simply place the relay after board wash and hand solder if it is a low volume item.

author: jitter
author_rank: Frequent Contributor
timestamp: September 05, 2015, 04:39:06 pm
content: That was indeed considered, but in the end cleanliness of the board and parts is very important for the application. The decision was made to hand solder the relays on the boards before the washing process. Since that change in the production process we have never had these problems again.The decision to do it this way was not mine and I didn't agree with it. We had soldered these relays for many years on the wave soldering process without any problems, and the change to the leadfree solder hadn't affected that. I would have spent more time on finding out what went wrong with our wave soldering process and thereby tackling the real problem and not the symptoms.Each board has 11 relays, so 88 pins to hand solder, normally produced in batches of 100. That costs much more time and a pin gets forgotten once in a while only to be discovered during the test (by which time it is mounted on a big heatsink and shoved inside a device).

author: jitter
author_rank: Frequent Contributor
timestamp: September 07, 2015, 06:34:00 pm
content: Quote from: Quarlo Klobrigney on September 05, 2015, 10:09:59 amHere are some pictures of part of the underside of the relay. There's at least one lead which clearly shows oxidation, to me that's a strong indicator that moisture damage may have occurred.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: September 07, 2015, 06:40:15 pm
content: Looks all the world to be cheap Chinese plating that.Or in American: Inferior plating of defective base metals which caused oxidation between the two, resulting in separation during heating in the soldering process.

author: jitter
author_rank: Frequent Contributor
timestamp: September 07, 2015, 06:58:26 pm
content: If that is truly the case, then a giant global manufacturer has some quality issues. That should also show up on the next batch of relays we already have in stock, as I wrote before. So: to be continued...We're talking about relays that are suitable for use in measurement and test equipement, which is the application we use them for.I'm not ready to reveal the type yet, but I will say that the Omron G6K-series is a similar competitor. These also gave problems, BTW, again because of moisture issues. This time the supplier was at fault, they had not treated them as moisture sensitive devices, and at our company they weren't identified as such either. Somehow people don't regard relays as moisture sensitive, but these small ones definitely are, whether they're from Omron on manufacturer X...

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: September 07, 2015, 07:10:21 pm
content: I understand the not revealing part.If, and if, they are Omron, I would be very surprised as I have always known them to be of good manufacture.Unless these are counterfeit, talking to the local rep will hopefully fix the problem.Keep us posted please, I'm sure we'd like to know the outcome.