What to use to solder wire to double sided PCB? - Page 1
Forum section: electronics / beginners

author: SharpEars
author_rank: Unknown
timestamp: August 10, 2015, 05:04:35 pm
content: I have a PCB where I have several point to point wire connections. I am using 18 AWG (<1.0237 mm) stranded wire which just barely goes through the 1 mm holes in the PCB. Note that I have multi-amp power (e.g., 7.5 A) flowing through these wires, so I need to stay "thick".The problem is that I want to solder the wire on both sides of the PCB, so what I am doing is removing enough insulation to expose the tinned copper of the wire above and below the PCB and soldering to that. Unfortunately, this fries some of the insulation that is near the solder point where the wire enters the PCB, due to proximity with the soldered joint.Also, the PCB hole spacing is 2.54 mm (this is one of those project PCBs that just has a rectangular array of circular solder pads on both sides and you connect them with wires or solder bridges). This means that if I have wires in adjoining holes, there is very little clearance and the possibility of a short from the wire exposed at the melted insulation points.There must be a better way to do this - perhaps some sort of a pin or something that can easily go through one of the holes in the PCB and be solderable on both sides (one side to the wire which wraps or plugs into a cap or crimp connector and the other side would just be a pin that produces from the bottom of the PCB that I can solder to). I think they used something like this way back when for point to point wiring on PCBs, but I can't find anything like that these days - or maybe I don't know what to search for.If you have any experience in this, please help.

author: IanB
author_rank: Super Contributor
timestamp: August 10, 2015, 05:08:39 pm
content: I think the "some sort of pin or something" you are looking for is called a turret. A search should turn up plenty of options.

author: SharpEars
author_rank: Unknown
timestamp: August 10, 2015, 05:24:27 pm
content: Quote from: IanB on August 10, 2015, 05:08:39 pmI am finding some. The problem is that I need a turret with a 1 mm pin that has a larger head able to accommodate a wire that is 1.0237 mm (turret inner diameter on the wire receiving end). Everything I am finding is cylindrical (i.e., top part diameter = bottom part diameter).

author: alsetalokin4017
author_rank: Super Contributor
timestamp: August 10, 2015, 05:30:34 pm
content: You could try this:Tin the stripped and twisted wire end, and the hole pads on both sides of the PCB so that the hole is filled. Then heat one side of the hole to melt the solder while you push the tinned wire end through the hole from the other side. When the wire end is through the hole, keep heating for a second or two so that the solder bonds to the tinned wire on both sides.Practice makes perfect. Consider using solid wire instead of stranded.

author: SharpEars
author_rank: Unknown
timestamp: August 10, 2015, 05:33:02 pm
content: Quote from: alsetalokin4017 on August 10, 2015, 05:30:34 pmI tried this method, but I am using stranded wire and when the wire barely fits through the hole, starting with a soldered hole and melting it enough to push the wire through without catching any strands is nearly impossible. It's already pretty hard. Maybe trying to use stranded wire is really a fool's errand here or I need to drill the holes slightly larger.I'll try to put a picture up later of what I am trying to do...

author: continuo
author_rank: Frequent Contributor
timestamp: August 10, 2015, 05:57:28 pm
content: Quote from: SharpEars on August 10, 2015, 05:04:35 pmOne like this?Isn't it possible to drill the holes for these wires just a little bit bigger, say 1.3mm? You could then insert one of these uninsolated wire ferrules, solder it on both sides of the board, insert your wire into the ferrule and solder it from the bottom?

author: SharpEars
author_rank: Unknown
timestamp: August 10, 2015, 06:02:10 pm
content: Quote from: continuo on August 10, 2015, 05:57:28 pmYour picture didn't transfer, but yes, one like this:http://www.aliexpress.com/item-img/shipping-to-worldwide-5x8cm-breadboard-PROTOTYPE-double-Side-Copper-clad-prototype-pcb-Universal-Board-pcb-manufacturer/1355055489.html#

author: eas
author_rank: Frequent Contributor
timestamp: August 10, 2015, 08:42:17 pm
content: Simple question: Why not just trim off some of the strands until it fits? Yes, the resistance will by higher, for 1-2mm. But before even worrying about that, what's the cross-sectional area of the traces you are soldering to?Something else to consider: Thick stranded wire can soak up a lot of solder. I've noticed that in some of the regulated DC power bricks I've taken apart/converted, they use some sort of crimped sleeve on the wire end, and then solder that into the board.

author: SharpEars
author_rank: Unknown
timestamp: August 10, 2015, 08:49:45 pm
content: Quote from: eas on August 10, 2015, 08:42:17 pmThis crimped sleeve you mentioned may be just the thing I am looking for! The pine that is soldered into the board has to be <= 1mm, though.

author: Chris C
author_rank: Frequent Contributor
timestamp: August 10, 2015, 11:58:17 pm
content: Another idea. Perhaps you could use a wire with an alternate insulation material, such that it doesn't melt at your soldering temperature, and so can't present the possible shorting issue. (Or reinforce the existing insulation at the ends with heat shrink, kynar tape, etc.)

author: SharpEars
author_rank: Unknown
timestamp: August 11, 2015, 12:56:16 am
content: Quote from: Chris C on August 10, 2015, 11:58:17 pmYep, thought of the heat shrink idea and may just do that. The problem is remembering to put it on both ends, BEFORE they are both soldered to the board.

author: Chris C
author_rank: Frequent Contributor
timestamp: August 11, 2015, 01:21:34 am
content: Quote from: SharpEars on August 11, 2015, 12:56:16 amI'm glad I'm not the only one that forgets.Regarding turrets, common female machine pin headers might work. Here's a dimensional diagram:http://www.4uconnector.com/online/object/4udrawing/05933.pdfRemove the plastic, and you have turrets. Though I haven't tried with this style of header, I can generally remove header pins by heating to soften the plastic, then pulling/pushing.

author: SharpEars
author_rank: Unknown
timestamp: August 11, 2015, 01:41:20 am
content: Quote from: Chris C on August 11, 2015, 01:21:34 amSadly, too small with a pin diameter of 0.5 mm (I need 1 mm). The 0.9 mm female side is too narrow for the 18 AWG wire I am using (unless I pull strands off). But it's an interesting idea, nevertheless...

author: IanB
author_rank: Super Contributor
timestamp: August 11, 2015, 06:03:34 am
content: I remember seeing this video before. It may offer some tips?http://youtu.be/Mrhg5A1a1mU

author: SharpEars
author_rank: Unknown
timestamp: August 11, 2015, 01:42:57 pm
content: Quote from: IanB on August 11, 2015, 06:03:34 amWow, this is among the best instructive videos I have ever seen. I actually learned a thing or three here that I didn't know. I think I am going to go and watch all of the videos in the series, because the quality of instruction isphenomenal.