Need advice/help on 0.4mm pitch SMD soldering - Page 1
Forum section: electronics / beginners

author: troop231
author_rank: Contributor
timestamp: November 23, 2013, 05:08:16 pm
content: Hello, this is my first post here, and I'd like to say thank you in advance for taking the time to help me out. I'm wrapping up my first project, and am frustrated that I cannot get my last connector soldered onto the board without the pads bridging together. This is a 0.4mm pitch, 30 pin, board to board connector. I'm using Chip Quik Low Melting Lead Free Solder Paste, and that seems to be working quite well, based on good results from a 0.8mm pitch connector. I'm using a toaster oven, and it seems to be working just fine for my needs.I try to fix the solder bridges on the 0.4mm connector with my soldering iron, but no matter what I do I simply cannot get them fixed without ruining the connector. This may be a result of finding it impossible to apply the solder paste in the correct amount onto the pads; using a toothpick I run a string of paste over the length on each side of the 15 pins. Even this still seems like too much paste, and therefore creates bridging. After ruining several connectors and wasting hours of time, I'm getting a headache over this, and thought I would post here for help.It stinks being this close to wrapping up my project. Thank you again for your time and help! Here's two pics of what I'm dealing with (the second pic shows the connector loose on the board, as I had to remove it using Chip Quick SMD removal alloy):

author: M0BSW
author_rank: Frequent Contributor
timestamp: November 23, 2013, 08:20:39 pm
content: Try these it may help you, these are by Alan W2AEWand this one

author: troop231
author_rank: Contributor
timestamp: November 23, 2013, 08:56:46 pm
content: Quote from: M0BSW on November 23, 2013, 08:20:39 pmThank you for the video links. So do you think I should try manually soldering it instead of toaster oven reflow?

author: M0BSW
author_rank: Frequent Contributor
timestamp: November 23, 2013, 09:08:43 pm
content: I've never tried the oven reflow , but I do use the methods in these video's, which works for me.

author: troop231
author_rank: Contributor
timestamp: November 23, 2013, 09:14:13 pm
content: Quote from: M0BSW on November 23, 2013, 09:08:43 pmThank you for your suggestion. I may need to simply order a hypodermic needle for my solder paste, as the included one is way too big.

author: Monkeh
author_rank: Super Contributor
timestamp: November 23, 2013, 09:30:56 pm
content: Quote from: troop231 on November 23, 2013, 09:14:13 pmhttp://www.ebay.com/itm/121126252031

author: troop231
author_rank: Contributor
timestamp: November 23, 2013, 09:35:44 pm
content: Quote from: Monkeh on November 23, 2013, 09:30:56 pmI just ordered some 30 gauge (0.3mm) needles on ebay from the same state I live in, so hopefully those will do the job.

author: Monkeh
author_rank: Super Contributor
timestamp: November 23, 2013, 09:36:32 pm
content: Quote from: troop231 on November 23, 2013, 09:35:44 pmThat should work nicely. Steady hand and clean pads (I trust you've got some wick).

author: troop231
author_rank: Contributor
timestamp: November 23, 2013, 09:44:10 pm
content: Quote from: Monkeh on November 23, 2013, 09:36:32 pmIndeed, and flux as well. The needles are slightly larger than the pad size (pads are 0.22mm width) but hopefully it will do the job.

author: Monkeh
author_rank: Super Contributor
timestamp: November 23, 2013, 09:46:19 pm
content: As long as you only apply a tiny amount and don't let it spread out when you place the connector, you should manage..If not, youcan get smaller.

author: mtdoc
author_rank: Super Contributor
timestamp: November 23, 2013, 09:56:02 pm
content: Quote from: Monkeh on November 23, 2013, 09:36:32 pmFYI, The inner diameter (lumen diameter) of a 30 gauge is 0.159 mm.

author: troop231
author_rank: Contributor
timestamp: November 23, 2013, 09:58:51 pm
content: Quote from: Monkeh on November 23, 2013, 09:46:19 pmYeah, hopefully. I couldn't find smaller needles locally (Hong Kong takes awhile). If I got somewhat decent results only using a toothpick and spreading the paste out all at once, I can't imagine how well the new needles will do when I put the paste individually on each pad.

author: Monkeh
author_rank: Super Contributor
timestamp: November 23, 2013, 09:59:18 pm
content: Quote from: mtdoc on November 23, 2013, 09:56:02 pmAh, see, there you go.Stupid arbitrary gauges.

author: mtdoc
author_rank: Super Contributor
timestamp: November 23, 2013, 10:06:34 pm
content: Quote from: Monkeh on November 23, 2013, 09:59:18 pmLOL - yeah well..I have no experience using solder paste but based on experience pushing other things through small needles, I would worry that something with high viscosity would be difficult to push through a 30 gauge needle.You could go up to a 27 guage needle with an I.D. of 0.21 mm ...

author: Monkeh
author_rank: Super Contributor
timestamp: November 23, 2013, 10:07:58 pm
content: Quote from: mtdoc on November 23, 2013, 10:06:34 pmThe ones I've been using are 0.25mm and are no trouble.

author: troop231
author_rank: Contributor
timestamp: November 23, 2013, 10:29:22 pm
content: Hopefully I won't have to order any more needles. I'm already in far deeper into this project in time and money than I would like, lol but that's what a project is supposed to be like I guess

author: GreyWoolfe
author_rank: Unknown
timestamp: November 24, 2013, 03:07:43 pm
content: I have been using a hypodermic needle for years to apply flux. It works great for precise placement. It should work great for precise placement of the solder paste also. Good luck.Tom, NW0LF