Using SMD solder paste to on pc board that contain no smd on pc board

Thread Starter

mrel

Joined Jan 20, 2009
170
Hello
I have few questions about solder paste.
(1) On ebay when seller sell solder paste does that mean contain solder mix with flux in a tube.
(2) Can I use solder paste meant to be use on SMD parts,on pc board that has regular resistor and capacitor that had leads come out on back side of the pc board ,from there i put solder paste on leads and use a hot air gun to melt solder paste,would that work?
mrel
 

jbeng

Joined Sep 10, 2006
75
You are correct, paste solder is a mix of tiny solder beads and flux in a tube.

Although standard wire-type solder would be preferred, paste solder can be used on a regular board with through-hole components. A hot-air gun is not necessary; you can use a standard pencil-type soldering iron. I would likely recommend using an iron in this instance in order to keep the soldering heat localized to the joint you are soldering. You will probably have to experiment with how much paste to apply to get a good solder joint. As a final note, it will probably be messy, so the board will likely need cleaned afterwards.
 
Last edited:

ebp

Joined Feb 8, 2018
2,332
How well it might work will depend on how you apply the solder paste. If you try to use a stencil as you would for surface mount components, it is unlikely you will get sufficient solder for good quality joints. Good joints also depend on all parts sufficiently hot. Unless you have a high-power heat gun, which means you must be careful to avoid overheating, you may well find it takes more time than soldering with wire solder and a soldering iron. It would certainly take me at least as long to manually apply solder paste to a bunch of through-hole pads as it would to make the joints with an iron.

I would not recommend using a soldering iron unless you first heat the board sufficiently to evaporate the volatile compounds from the paste. If you don't they will boil and cause spattering as soon as you apply the iron. I can't make a good recommendation for how much time should be used at what temperature. It would depend on how much paste is applied and whether it is a more-or-less uniform layer or a "blob."
 

ian field

Joined Oct 27, 2012
6,539
Hello
I have few questions about solder paste.
(1) On ebay when seller sell solder paste does that mean contain solder mix with flux in a tube.
(2) Can I use solder paste meant to be use on SMD parts,on pc board that has regular resistor and capacitor that had leads come out on back side of the pc board ,from there i put solder paste on leads and use a hot air gun to melt solder paste,would that work?
mrel
Unless you got a really sweet deal - solder paste is usually too expensive to waste on through hole assembly.

Its probably more difficult to impart heat to as well as heating the wire and pad. i'd probably expect messy results.
 

MisterBill2

Joined Jan 23, 2018
7,325
I have done it, using the solder in a flux miwhen the stuff was far to old for it's intended use. It will work but it is not cost effective, and it is messy.
I have also used it to solder surface mount parts , using a soldering pen. That works but it is still a bit messy.
 

ArakelTheDragon

Joined Nov 18, 2016
1,350
By PC board, you mean a computer board? I have never seen a computer board that is not with SMD components? On top of that its multi layer and your solderer that's 40w might damage it.
 

MisterBill2

Joined Jan 23, 2018
7,325
By PC board, you mean a computer board? I have never seen a computer board that is not with SMD components? On top of that its multi layer and your solderer that's 40w might damage it.
No, not a "computer board, but a first attempt prototype board, about the diameter of a US Dime coin, with a small processor, an op-amp, and a voltage regulator IC. Regular computer circuit boards are all multi-layer and as a result they are not any fun to work on.
 

ArakelTheDragon

Joined Nov 18, 2016
1,350
No, not a "computer board, but a first attempt prototype board, about the diameter of a US Dime coin, with a small processor, an op-amp, and a voltage regulator IC. Regular computer circuit boards are all multi-layer and as a result they are not any fun to work on.
Like this it makes since.
 
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