Soldering smd module on pcb


I’m looking for a guide and equipment/tools recommendation for soldering an smd module on a PCB, specifically the module I’d like to solder is the WT41e-U.


You’ll be fine with a sharp soldering iron. Or paste + hot air station or reflow oven if you’re doing many.

Pads connected to GND may be hard to heat by too sharp soldering iron. Specially if at main PCB they are also connected to GND zone. I have soldered one module made that way. I replaced sharp iron with the one about 1mm width and flat at front to touch it pararelly to hitted pad.

1.27mm is more common pad distance than 1.5mm and isn’t difficult with “a sharp soldering iron” as halachal said.

IMO the most difficult part, if you do it with iron, is to place the module in exactly right spot and keep it there until the first pad is soldered. Until then even smallest wrong move cause it to slip to wrong location - although 1.5mm P may help here, I have done only 1.27mm. And the boards have been such that they couldn’t lay down evenly on flat surcface (the module in the back side, other compoents in the front side). Moving makes the module pads and the board pads to misalign so that it easily causes solder bridges.

If you do only one or two boards and for your own use, you could invent something to help. Like putting
THT pads to each corner and a pin header pin through each of them. That would keep it in place easily.

And, as Piotr said, GND (or other zone) connections are problematic. Thermal reliefs are must.

This tools will help you a lot, use flux like there is not tomorrow, put a bit of solder on a corner pad and fix the module, then, fix the opposite corner, once it is fix, do the rest.


and if you have solder paste and a reflow oven, do it like this: :slight_smile:

Have fun!

I personally prefer the solder iron tips with the angled face. Something like this:

They can be used like a chisel tip or a fine (pencil point) tip depending on how you turn the iron.

And buy good solder wire and good flux.

At that point I expect few corrections (each time heating that pad) until module is positioned correctly.

Typically I use much sharper tip. This one:

I solder very rarely and as I remember I was really soldering only 0603 recently.
If I have something bigger to solder I use 110W trafo soldering iron (bought in 1980).
But it is not the decisions based on “how to equip the workbench” but just historical consequences.

Yes, I did a very broad description but as you said, you fix the corner, then, you notice that it is not straight, and heat it again an move it, then you curse, because you move it too much, heat it again and try to move it back, the more coffee you drank the more repetitions you will need to do :slight_smile:

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After soldering dozens or maybe even hundreds of modules to a certain kind of board I have learned how to pinch the board and the module between my thumb and fingers so that I can move it in place with the other hand, then keep it pinched until I have soldered the first pin with the iron. The tin must be pre-applied to the iron tip for that to work because I can’t handle tin wire at the same time. The rest I do under a stereo microscope.

The iron tip is a cone, not as long and sharp as in the pictures above. A different kind of tip might be better, this is just a general purpose tip with which I solder 0402 and most other components, including THT.

When I have this problem, a half shot of whiskey does the trick


My reflow oven would not do the job becouse module screens the heat from above (same as BGA) Try to find someone with a vapour phase machine

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