smd chip soldering .5 mm - Page 1
Forum section: electronics / projects

author: NotANewbie
author_rank: Contributor
timestamp: April 14, 2015, 01:41:17 am
content: I'm having trouble soldering in a .5mm pin spacing smt chip.It is driving my crazy. The videos make it look so easy! I watch Dave's video, they are good, but it just isn't working for me on this board.I've done others that worked ok, the solder wick is usually what I need, but isn't working here.I'm getting some adjacent pads with connectivity. Looking at the chip with two levels (well three if you count my glasses) of magnification,I can't SEE any bridging of the pads.Just not sure what I can do. After about 4 hours and two chips destroyed starting over, one board now a bit messed up, and I only have three,so can't mess up another one. Appreciate any suggestions.

author: qwaarjet
author_rank: Regular Contributor
timestamp: April 14, 2015, 01:44:09 am
content: temp on the iron?type of solder being used?tip type?

author: NotANewbie
author_rank: Contributor
timestamp: April 14, 2015, 01:50:20 am
content: I'm using a fine pointed soldering tip, I saw Dave recommended a flat tip, but don't have one, would have to take a long drive to get one.I use some .022 solder. I've tried a few different methods.Just tin the pads, put the chip on, and heat them, but even this is bridging some pads.

author: qwaarjet
author_rank: Regular Contributor
timestamp: April 14, 2015, 02:04:54 am
content: what alloy of solder are you using? 63/37, 60/40, some awful silver blendDoes it a flux core?Those fine tip conical are almost useless for normal solderinggenerally adding flux helps a lot250-350C should be good temp to go with barring part limits

author: georges80
author_rank: Frequent Contributor
timestamp: April 14, 2015, 02:10:02 am
content: LIQUID FLUX is what you need. Wet the area with flux, you can't have too much.... Flat chisel tip and lightly tinned and drag along the pins (after tacking a couple of diagonals down to lock the chip in place.I use Kester 2331-ZX organic flux, amazing stuff, but you MUST CLEAN/WASH the board after soldering is complete since the flux is a) partially conductive and b) a little corrosive.cheers,george.

author: tonyarkles
author_rank: Regular Contributor
timestamp: April 14, 2015, 03:39:58 am
content: My routine for cleaning up bridges afterwards is to put a little bit of extra flux onto the tip of the braid and use that to suck it up. Might help?Also, how well is the chip aligned? I've had issues before where my alignment was off just a little bit. Pins on one end of the chip looked fine, but on the other side the pins were landing half-way between the pads.

author: Psi
author_rank: Super Contributor
timestamp: April 14, 2015, 06:21:16 am
content: Quote from: NotANewbie on April 14, 2015, 01:50:20 amIt won't bridge if you clean the iron before each joint. Its the solder that come off on the iron which makes bridges when reflowing tinned pads to tinned legsThe PCB isn't silver plated is it? Those can be a bitch when the silver oxidizes

author: Dago
author_rank: Frequent Contributor
timestamp: April 14, 2015, 06:52:43 am
content: Flux flux and more flux. None of that flux pen crap, proper liquid or gel flux.

author: radioFlash
author_rank: Regular Contributor
timestamp: April 14, 2015, 11:02:19 am
content: If you have and have a junk pcb laying around, it might be helpful to practice on it to test your process before you use your project pcb.

author: Rick Law
author_rank: Super Contributor
timestamp: April 14, 2015, 08:23:36 pm
content: Quote from: radioFlash on April 14, 2015, 11:02:19 amOld useless cell phone is a good practice target for 0.5mm. I had 2 Startac cell phone (dated around transitioning NiMH to Lithium). Plenty of small chips to work on.I had practiced soldering and desoldering SMD's in the sub-1mm pitch on that two dead cell for at least 50 cycles of de-solder then solder small chips back on. A month later, I did my first two SMD chips for real (0.5mm VSSOP 10 pins, 0.9mm SOT23-6), it went well the first try.Practice is the key.Oh, practice and patience are the keysOh, practice, patience and good lighting are the keysOH... never mind, no body expects the Spanish inquisition anyway...

author: NotANewbie
author_rank: Contributor
timestamp: April 14, 2015, 09:03:44 pm
content: I appreciate all the suggestions! I went out and bought a couple new flat tips, they do make it easier.But I discovered the problem, and its a little embarrassing..the chip was put on upside down.And because it has a few two leads that share a connection, it laid out so the two pins straddled connections when upside down,so it looked like a pin bridge. So now it makes sense, as I could not see a solder bridge no matter how I tried.I blame the datasheet, as it shows the chip upside down with pin 1 on the bottom right instead of top left.

author: Rick Law
author_rank: Super Contributor
timestamp: April 14, 2015, 09:08:26 pm
content: Quote from: NotANewbie on April 14, 2015, 09:03:44 pmSo, not big deal, just feed it -5V instead of +5V and off you go.(Sorry, can't resist...)