Solder, Flux, and Cleaning Discussion

[Hartono]

here I present my current step by step practice for soldering smd:

1. solder the PCB pad with low temperature solder, usually silver loaded solder do have lower melting temperature, it doesn't need to be "audiophile stuff" but I have very good result with cardas, which melt and solder very nicely, it didn't clump up like paste while cooling if you know what i mean.

2. use solder wick to get to remove excess solder, so the pad will only have slight solder there, try your best not to do too thin nor too thick.

3. use 99% isopropyl alcohol with some sort no cloth to remove solder flux on the board, you might need to do a few time, some people says 90% alcohol is not good enough and will left some residue, but you might be just fine, 99% is the one you want though.

4.Clean your solder tips thoroughly using wetted sponge.

5.Put the smd component on the spot, with some helping hand of your preference, I use tiny blu-tac blob put on a tip of toothpick, this work reasonably well, make sure the blu-tac is as far away away from the solder heat while doing this.

at stage no 5. do not add extra solder, if you do you will leave excess flux which can left under the component side. Excess flux under the component have various detrimental effect.

as SMD component usually come pre-tinned, no flux while soldering them should not be a problem, the main problem is the PCB which quickly get thin layer of corrosion and cause imperfect joint.


good luck !!

[Hartono]

Originally posted by djQUAN
I also have 0.3mm flux cored solder but there are portions that there aren't any flux in them.

so what I did was run 6 strands of 0.1mm solid core solder together (much like litz wire) and use that along with dipping it in a pot of solder paste before soldering. then I would clean the board after soldering.


if you can get the solder practice kit from Jan, I suggest you do since 0.8mm for SMD parts is not too difficult once you get a bit of experience.

yes I also did the same litz thing with my solder most of the time, it seems to help the fluxing process to spread more effectively than single big solder wire.

how did you clean your board ? any good advice ?

[BWRX]

0.020" (0.5mm) diameter flux core solder is a good size to use for hand soldering surface mount components. Ultrasonic cleaning is the best way to clean boards but Isopropyl alcohol, a brush, and a lint free cloth work well for most of us.

[Hartono]

thanks for the advice BWRX,

I also did basically the same thing, but I'm very nit picking about cleaning flux thoroughly, might diy solvent ultrasonic agitation one day.

I'm just worried the ultrasound damage component and IC

[djQUAN]

for board cleaning, I use a lot of laquer thinner. put a lot on a tupperware type container, enough to cover the board, then agitate for 10-30min depending on how clean I want the board. do this in a well ventilated area.

if I don't need a very very clean board, a small amount of thinner and a paint brush is enough for most cases.

[BWRX]

If the ultrasonic cleaning is done properly it shouldn't do any damage.

The key to cleaning with alcohol is to remove the dissolved flux with the lint free wipe/cloth. I've seen a lot of people just use a brush and alcohol but all that does is move the flux residue all over and make the board sticky.

[djQUAN]

I've seen a lot of people just use a brush and alcohol but all that does is move the flux residue all over and make the board sticky.

I use the thinner and brush method but that doesn't leave my boards sticky. you just need enough thinner.

[Hartono]

BWRX:

"If the ultrasonic cleaning is done properly it shouldn't do any damage."

I'm searching the way to do it properly I read somewhere that the frequency used for cleaning jewelry and PCB is not the same, PCB use lower frequency, that might explain it. I felt the agitation on the jewelry is way too strong and too high frequency, which I'm really worried.


"The key to cleaning with alcohol is to remove the dissolved flux with the lint free wipe/cloth. I've seen a lot of people just use a brush and alcohol but all that does is move the flux residue all over and make the board sticky."

Agree on this one, also did this with various degree of success. I'm just very worried (I should change my nick-name to paranoid ) about the "Ionic Activator" thing left on the board , do you know how to remove this properly ?


djQUAN

Thinner ??


I don't really know if thinner is safe for the PCB and component or not, It can damage some component ?? no ?? or damage the solder mask surface ?

Thinner is pretty strong stuff. Be careful man

For my "nice" warning,you should send me some :
Kalamansi, Bagoong, and Lechon

[Hartono]

Originally posted by Hartono


yes I also did the same litz thing with my solder most of the time, it seems to help the fluxing process to spread more effectively than single big solder wire.

how did you clean your board ? any good advice ?

wait I make a mistake in my earlier post,

what I mean is : I use a few flux cored solder twisted together, not solid cored ones to make litz, this works very well for larger soldering task ( Non SMD)

[BWRX]

Originally posted by djQUAN
I use the thinner and brush method but that doesn't leave my boards sticky. you just need enough thinner.

I'm sure thinner would remove flux but, like Hartono mentioned, it might also remove other things you don't want it to! I wouldn't recommend using lacquer thinner for cleaning because it is much more aggressive than alcohol and it is not nice stuff to handle and use. Pure Isopropyl alcohol works very well at dissolving flux and has the added advantage of not being toxic and can evaporate very quickly.

Originally posted by Hartono
I'm searching the way to do it properly I read somewhere that the frequency used for cleaning jewelry and PCB is not the same, PCB use lower frequency, that might explain it.

Most ultrasonic cleaners for electronics work around 40kHz and are lower power (maybe around 10W/liter?). Ultrasonic jewelry cleaners are usually quite a bit more powerful and can do damage to components.

Originally posted by Hartono
I'm just very worried (I should change my nick-name to paranoid ) about the "Ionic Activator" thing left on the board , do you know how to remove this properly ?

I'm not sure what the "Ionic Activator" is?