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Mwgasquirt soldering question

412 Views 2 Replies 2 Participants Last post by  Turbo84Voyager
I assembled my jim stim last night and everything went great except for a few solder joints. Almost all of the solder joints soldered great. I had a few ( about 8 out of the 200+ ) that for some reason the solder did not want to flow well. The solder would not flow into the hole but rather flow towards the iron. The components were hot enough and I had the iron set to 675 F. I am using 60 40 rosin core. I tried hotter temperatues and they still did not flow right. I desoldered and tried to resolder and had the same results. Several of them I was able to quickly solder on the component side and several of them sucked the solder right in like it should on that side. It makes me think there was some type of contaminant on the board. I am pertty confident the connections will be fine especially just for testing, I ran the jim stim tests and all works fine, but I dont want to run into this prob with the ECU build. Is there something should be cleaning the board with prior to soldering? Any advice would be appreciated.


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Some solder joints on the board are connected to large copper traces, these tend to be the high current traces. In these cases, it'll suck the heat away from the joint, into the copper, faster than normal, making to very difficult so get solder to flow into the still cold joint.
I tend to turn the heat up quite a bit, like 800F for the big components, like the two big diodes, and the MOV. Or generally any time I have a joint that's being a PITA. When you turn up the iron, give the iron a couple minutes to fully get up to temp, you need the tip good and heatsoaked so that it can dump it's heat into the joint. Make sure it's good and freshly tinned before you hit the joint, as at that temp, it burns the flux off the tinned tip pretty quickly.
The MS board is actually really good about this, they designed heat isolators around most of the big connections for this exact reason. I've dealt with other boards where it took nothing less than a 200watt soldering gun to get solder to flow into joints directly on the ground plane.
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Thanks for the info. I cranked up the heat, not quite to 800 but much higher when I did these last night and it did help, the joints dont look as nice as the others but they are nice and shiny and I dont see any cracks
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