Rework and heating of aluminium organic polymer capacitors - what to know? - Page 1
Forum section: electronics / general

author: julian1
author_rank: Frequent Contributor
timestamp: August 27, 2024, 09:51:12 pm
content: I want to switch from TH wet-electrolytics to modern SMD parts for bulk capacitance.For normal prototyping/rework with a hot-air gun, I will de-solder or use polyamide tape for nearby wet-electrolytics - to limit heat exposure.But for aluminium polymer capacitors, I believe they are more robust, and designed for automated SMD reflow processesAlthough manufacturing guidelines still suggest to limit reflow cycles to avoid performance/ESR/lifetime deterioration.But to be certain - those sealed aluminium cans look intimidating.Is it correct, they pose no risk of exploding (unlike wet-electrolytic), if a hot-air gun is used near them?

author: coppercone2
author_rank: Super Contributor
timestamp: August 27, 2024, 10:12:03 pm
content: anything can explode if there is moisture in it.Polymer capacitors are basically more robust in every wayI think it could only explode if there is a defect, but a defect is always possible.You have no way of knowing, so wear goggles as usualIf you ever deal with large amount of chemical fluid, its easy to realize how water can possibly slip into a assembly line.The 500mlL chemistry lab bottle has a extremely low chance of water ingress. However, a 55 gallon or often much larger drum, shipped through ports trains and sometimes even pumped from cisterns, can let water slip through QC. All it takes is 1 guy to think another guy did something.My recommendation : make your decision based on the maximum pressure rating of the container. If there happened to be steam in there, do you feel threatened by the explosion? if so, wear protection. I think you already answered your question for yourself.But even small containers right.. like reagents. Lets say its in a wear house and the one above it sprung a leak and left some residue on the bottle. Naturally, the cheap skate running the place is gonna tell his guy to hold it under the sink to wash it off because its sealed, possibly even scrubbing it while prodding residue with a sharp pick to make it look good. If the seal is weak, its possible water got into your bottle.return of the living dead serves as a good learning video about this

author: coppercone2
author_rank: Super Contributor
timestamp: August 27, 2024, 10:31:49 pm
content: and if you can find the right size, getting soldering tweezers reduces the risk of any explosion greatly.Pace resistance desoldering tweezers, or regular soldering iron tweezers are the solution.Face it, if you can avoid heating up a tank with chemicals (polymer or liquid or even solid), its better!I noticed.. its rather easy to over heat caps with hot air, so its a last resort for me.Keep in mind something, when they say for reflow soldering, their hoping that your doing it in an oven, which is a small blast chamber. Statistically if a small portion of their components vents, then it will mostly occur in an oven. That might be enough for some people to feel at ease with their product quality...... but its not gonna do you any good.. they have a statistical approach to safety in companies, it regards money and liability, not you.

author: julian1
author_rank: Frequent Contributor
timestamp: August 28, 2024, 10:35:17 pm
content: Thanks, taking extra care is probably warranted, and they should be treated similar to wet electrolytics.Maybe a bit like plastic connectors.Treat them with kid gloves, wear eye protection, or at least turn ones head away to mitigate the shrapnel if it goes wrong.Interestingly, I noticed the datasheets for the hybrid polymer types which are a combination wet/solid specify similar conditions for their reflow profiles.

author: coppercone2
author_rank: Super Contributor
timestamp: August 28, 2024, 10:36:33 pm
content: their said not to explode, I am just saying that's only if the design is correct.It can't hurt to over heat one and see what happens under controlled conditions instead of speculation. There is polymer and polymer hybrids too. But even if you get a good result you like, I still think basically all pressure vessels can fail badly with water or contaminants. If it can hold pressure it can fail...