I've not seen one of these before. - Page 1
Forum section: electronics / beginners

author: orbiter
author_rank: Frequent Contributor
timestamp: April 11, 2011, 05:17:59 pm
content: Hi all,Had a lil' problem today with a chip I was trying to remove from an old circuit board, basically I'd just put a new element in my heat gun and it's first job was on a small project I'd had in mind for a while. The board I was working on was from an old Panasonic personal radio/cassette player that had been knocking around for ages. Anyway, I fired up the heat gun and using all my recently acquired skills got to work on some chip removal. However after a couple of minutes I was getting nowhere with this little bugger. I knew the heat gun was working & hot enough, but nothing was budging, all the other solder joints were surrendering & bobbing around like ducks in a pond, but this chip was having none of it. So.. I upped the temp to around 420*C to see if it would help, but still nothingAnyway now a little stuck for ideas I recalled a technique I'd seen on You Tube, were you basically you remove all the solder from the joint with braid, slide a strip of enamelled wire between the chips base and it's pins, then solder one end of the wire to an adjacent joint whilst pulling on the other end, sort of a cheese wire effect (yes this can damage the pins but didn't, & to be honest it wasn't a problem if it did.) So with all the pins released Imagine my surprise when the chip still wouldn't moveI guess you pro's out there probably know what's coming next, however please forgive my noobness here. Yes.. The chip had a damn connection on it's base, not only that but it looked as if it had some sort of adhesive holding it down too, unless that was just dried out hardened flux or something, but as you can see it was stuck down good & ripped the solder mask off when it came free.I don't know what the chip is as it's numbers have worn away, but I think it's from the tuner part of the circuit.

author: Strube09
author_rank: Regular Contributor
timestamp: April 11, 2011, 06:02:20 pm
content: Depending on the solder process they use, some manufactures have a glue that is placed under the component to keep them from moving during the solder process.I see this quite often. More than likely the board is dipped in solder and this keeps the IC from coming off.Strube

author: Neilm
author_rank: Super Contributor
timestamp: April 11, 2011, 06:24:33 pm
content: Quote from: Strube09 on April 11, 2011, 06:02:20 pmThis is quite often done on boards that have both through hole and surface mount on the same side. It means you only have to solder once.Looking at the picture I would suspect that there is not a connection to the chip - I think that the glue has stuck to a via under the device and when it came off it pulled off the resist on the track.YoursNeil

author: orbiter
author_rank: Frequent Contributor
timestamp: April 11, 2011, 06:54:37 pm
content: Ah I see, thanks for the feedback guys. I have had a scrape around on the board and it does indeed feel like some sort of glue type substance, I think it's too hard to be flux residue etc. Also I couldn't actually see any indication of solder on the top side of the board but the hole was full of something or other, I just assumed it was solder, but as you guys say It's probably just hardened adhesive.I've learned something new today Neil as I'd not seen or heard of these dual type package components before. Were they only around during a certain time when SMD's were being introduced or are they still manufactured today?Much appreciated fellasThanksJohn

author: armandas
author_rank: Frequent Contributor
timestamp: April 11, 2011, 07:36:09 pm
content: Quote from: orbiter on April 11, 2011, 06:54:37 pmThat looks like a standard 18-pin Small Outline IC (SOIC-18, SO-18) package, one of the easiest SMD packages to solder by hand. They are widely used today, but there is a smaller version called MSOP.

author: Time
author_rank: Frequent Contributor
timestamp: April 11, 2011, 08:05:37 pm
content: looks like a murder scene on PCB with a picture of the victim to follow. Death by thermal trauma.

author: orbiter
author_rank: Frequent Contributor
timestamp: April 11, 2011, 08:55:25 pm
content: Quote from: Time on April 11, 2011, 08:05:37 pmNooo. The death was with 200mm pliersEven with all pins lifted off of the pads, the chip still wouldn't come off. It was as if it had been stuck down with Araldite first.

author: Tony R
author_rank: Regular Contributor
timestamp: April 17, 2011, 04:46:57 pm
content: When i saw the picture i nearly cried... poor board... but yes it looks like the chip had been glued down and when you pulled up on it the pad of a via with some solder that filled it came up with it. nothing to surprising.