| Electronics > Beginners |
| Would solder paste or alcohol/IPA go inside an IC when soldering and cleaning? |
| << < (3/3) |
| bjdhjy888:
--- Quote from: MosherIV on August 16, 2019, 07:49:14 pm ---Hi. Getting back to the questions ask by the op. Here is a link with a nice diagram of the different parts of a microchip https://electronics.stackexchange.com/questions/28840/what-is-the-protective-layer-around-microchips-made-out-of/28845 There is little difference between the leg frame, whether it is DIL or QFP, j-lead etc when molding the packaging. It confirms what I remember, that the black plastic material is some kind of epoxy resign. It fully covers the entire silicone chip and the leg frame, only leaving the legs pertruding for soldering. The epoxy is non porous, so liquids like IPA do not effect it. I remember a colleague telling me that the change to RoHS meant that the epoxy used had to be re-formulated and the main difficulty was resistance to heat, ie survive soldering. --- End quote --- Thank you for your explanation. That said, just because an IC's casing is of epoxy and being non-porous does not mean the casing is water-proof or of IP67. So, I would still be concerned if liquid would leak inside an IC during soldering, causing damages. Am I correct? |
| bjdhjy888:
Speaking of alcohol v.s. IPA, I did an experiment for cleaning up, after I soldered my LQFT-48 chips last night. The result showed IPA was way more powerful, when it comes to removing leftover solder paste. Below you can see solder paste was still visial and hidden under the pins, whereas it's clean after using IPA. My question is, should I use IPA and quit using alcohol? IPA is bad for my health? Or, should I continue to use alcohol which is not harmful for my health, and I start to brush harder when cleaning my PCB? |
| T3sl4co1l:
Isopropyl alcohol is almost as low toxicity as ethanol is. Side-effects aren't as pleasant, of course... Acetone is essentially the same toxicity as well, because isopropanol is oxidized to acetone in the liver. MEK is also quite effective, though again it's more aggressive against a lot of plastics, inks and so on, so needs to be used even more cautiously. Avoid aliphatic (heptane, petroleum ether... gasoline?) and aromatic (toluene, etc.) solvents, they're very likely to damage things. Don't poo-poo the commercial flux cleaners. They're more expensive than solvents, because they work damn well. A few spritzes, a little scrubbing or sonicating, another spritz to clean it off and you're done. Huge labor savings. Tim |
| MosherIV:
--- Quote ---That said, just because an IC's casing is of epoxy and being non-porous does not mean the casing is water-proof or of IP67. So, I would still be concerned if liquid would leak inside an IC during soldering, causing damages. --- End quote --- No, fully encapsulating the silicone with a non porous material is suppose to make it liquid proof. The point of encasing the silicone chip is to a) protect the silicone chip, b) protect the bonding wires both mechanically and from contamination including liquids. The encapsulation has been designed to survive circuit board manufacturing. This means that the whole device has to survive reflow soldering : sitting on solder paste and going through infra-red oven for 20 minutes reaching temps of upto 250°C and finally being washed with commercial flux cleaner --- Quote ---Am I correct? --- End quote --- No! |
| Navigation |
| Message Index |
| Previous page |