Cleaning PCB after soldering

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paselfc
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Joined: Tue Jan 24, 2017 5:16 pm

Cleaning PCB after soldering

Postby paselfc » Tue Jan 24, 2017 5:29 pm

Hi
I have a question about PCB cleaning.
Which is the best way to clean the PCB after soldering?
Is it good enough with IPA (isopropyl) or with the Flux Remover spray?
We use a lead free solder wire (3,5% flux inside the core) and after the soldering its a visible wetting,flux around the joint.When using the Flux remover the surface gets clean but it leaves sticky on it (when touch with fingers).
Same things occurs when cleaning with IPA.
The PCB material is FR4
Anyone with solution?
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Ramon
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Re: Cleaning PCB after soldering

Postby Ramon » Wed Jan 25, 2017 11:17 am

Hello Paselfc,

Depending of the flux type used cleaning with IPA of flux cleaner may be sufficient. In general, liquid fluxes are easier to clean when compared to gel fluxes.
Whether you can use brush + solvent on the assembly is determined by:
- Flux type (Internal or External in types: Gel or Liquid)
- Soldering application (hand or machine soldering)
- Physical properties of components (enough clearance for a brush to enter?)
- Location on the PCB of the area to be cleaned

To start: Internal flux is the flux inside the solder wire or the paste. So when soldering there's always flux applied.

Analyzing the situation: We need to start at the soldering application to determine which solder process is used. This to determine if cleaning is required. For hand soldering goes: In general a hand soldering process with external flux is never a no-clean process. The operator will apply the external (additional) flux manually and the dispensed amount will vary on every application. For a soldering process to be no-clean, it must be guaranteed all flux has been activated when soldering.
With machine soldering, the heat is applied to the whole pcb and flux qty's are more defined. So a machine soldering application will more easily apply to no-clean conditions.

Driven by your other question, it is assumed we're addressing a hand soldering operation. So you must clean flux remains when external flux is used.
Depending on the physical properties (size, pin spacing etc) it could be impossible to clean with solvent + brush (eg. fine-pitch multiconnectors). Would the area to be cleaned by more towards the center of the pcb, one would only spread the flux residue over the area, instead of cleaning).
Would the hand soldering process rely on the sole use of internal flux (flux-cored solder wire), then there is a fair chance the pcb could apply for no-clean. For that matter it is advised to perform cleanliness tests (eg. IPC-TM-650 § 2.3.27) to determine if a cleaning cycle is in fact required.

General conclusion:
Brush & solvent could be a viable cleaning method in repair operations. On rework or assembly process manual cleaning is not advised. An operator could forget the cleaning step in the process or be less thorough on cleaning. Advise to wash pcb's after hand soldering with external flux in the assembly process. On handsoldering with internal flux, perform tests to determine if cleaning is necessary. The advised cleaning cycle of new assemblies is a washing method (eg. ultrasonic). Manual cleaning (for new assemblies) with brush and solvent is not reliable enough to guarantee consistent performance.
Keep calm and focus on soldering
Anderson
Posts: 16
Joined: Thu Feb 09, 2017 8:41 am

Re: Cleaning PCB after soldering

Postby Anderson » Thu Mar 16, 2017 5:25 am

I have found some good tools for cleaning of PCB at http://www.printtec.nl. However, I haven't purchase them yet but I think it might be good one. I also use Methanol (Methyl Hydrate) to avoid Lighter Fluid completely as it really useful for dissolving sticky residue.
totalmedtech
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Joined: Thu Jul 19, 2018 8:46 pm

Re: Cleaning PCB after soldering

Postby totalmedtech » Thu Jul 19, 2018 8:57 pm

i use METHYL HYDRATE 99.9 pure,it`s around 10$ a galon(3.78 litre),or u can use isopropyl alcohol for delicate boards (it`s usualy safer) as for price is somewhat the same
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DaveRodda
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Joined: Wed Nov 14, 2018 6:38 pm

Re: Cleaning PCB after soldering

Postby DaveRodda » Wed Nov 14, 2018 6:41 pm

I sometimes use an old toothbrush on the boards to get into the nooks and crannys. We also do drop boards into a ultrasonic cleaner with IPA. There is a caveat to this. If you have any parts which are not to be washed, this is not a good idea. Usually these parts are buttons or dip switches. The Datasheet will say. Also there are possibilities you may break a chip with ultrasonic. Most of the time I do not have problems, but when I do it's typically a crystal which dies.
Timothyper
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Joined: Fri Jan 25, 2019 5:41 am

Cleaning PCB after soldering

Postby Timothyper » Thu Jan 31, 2019 3:08 pm

A word about Simple Green or other cleaning concentrates. It will peel paint if you dont dilute it. It is an amazing de-greaser for engines, but I have first hand experience that it will peel paint.
edgetaf
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Joined: Fri Jan 04, 2019 12:49 pm

Cleaning PCB after soldering

Postby edgetaf » Sat Feb 02, 2019 12:30 pm

Im trying to make a cleaning wand to help clean my boiler after runs. Its a 24 X 1/2 copper pipe with a spray ball of sorts on one end and a female brass garden hose adapter on the other end. The spray ball is a piece of 3/4 X 1 pipe with a 3/4 cap on the end and a 3/4 X 1/2 reducer to connect it to the 1/2 pipe. No problem getting the spray ball nozzle soldered, but I cant seem to get solder to adhere to the brass hose fitting on the other end of the pipe.

Is there a method to get a good brass to copper solder join. What Ive tried is to treat it somewhat like soldering copper to stainless using liquid flux and silver bearing solder. I cleaned it well, applied flux, heated with a mapp torch, reapplied flux, reheated, and applied the solder. After cooling, the two pieces broke apart with very little force. Ive never tried soldering brass. Might I be doing something wrong?

Im using a homemade spray ball because I couldnt find one online small enough to fit my boilers 1 fill port. Going into it seemed like a simple thing to do, but as sometimes happens - what seems simple isnt always easy.
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Ramon
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Re: Cleaning PCB after soldering

Postby Ramon » Wed Feb 06, 2019 11:14 am

edgetaf wrote:Im trying to make a cleaning wand to help clean my boiler after runs. Its a 24 X 1/2 copper pipe with a spray ball of sorts on one end and a female brass garden hose adapter on the other end. The spray ball is a piece of 3/4 X 1 pipe with a 3/4 cap on the end and a 3/4 X 1/2 reducer to connect it to the 1/2 pipe. No problem getting the spray ball nozzle soldered, but I cant seem to get solder to adhere to the brass hose fitting on the other end of the pipe.

Is there a method to get a good brass to copper solder join. What Ive tried is to treat it somewhat like soldering copper to stainless using liquid flux and silver bearing solder. I cleaned it well, applied flux, heated with a mapp torch, reapplied flux, reheated, and applied the solder. After cooling, the two pieces broke apart with very little force. Ive never tried soldering brass. Might I be doing something wrong?

Im using a homemade spray ball because I couldnt find one online small enough to fit my boilers 1 fill port. Going into it seemed like a simple thing to do, but as sometimes happens - what seems simple isnt always easy.



Hmmm, soldering yes but this is construction soldering you refer to. Forum is about electr(on)ic soldering. So unlikely to find the best answer here.
Anyway, stay off of the silver bearing solder for tubing. These need very high temperatures so can be very hard.
Keep calm and focus on soldering

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