SMD soldering

[rullywowr]

I see. So if I could score some 70-90% IPA, would that do for cleaning 186?

TBH, I still cringe at the thought of running anything that has to do with electricity through water at any point.  I guess I'm just weird that way...

Most packages (opamps, resistors, diodes, IC's, transistors) are hermetically sealed and therefore waterproof.  No concerns there.  Pots and switches are another story as they often have openings where the inner workings can be exposed to water...

[pickdropper]

I see. So if I could score some 70-90% IPA, would that do for cleaning 186?

TBH, I still cringe at the thought of running anything that has to do with electricity through water at any point.  I guess I'm just weird that way...

Most packages (opamps, resistors, diodes, IC's, transistors) are hermetically sealed and therefore waterproof.  No concerns there.  Pots and switches are another story as they often have openings where the inner workings can be exposed to water...

Spot on.  I'd would also add trim pots and IC sockets to that list.  Sometimes people forget about IC sockets, but getting flux into them can cause problems.

If I have a board with those parts, I usually clean it before installing those, then I add them.

[wgc]

Rf is usually ok with no clean, as much as you can generalize rf, but high frequency rf is where the problems are. Might be that they dialed it in with the residue in place, and if automated should be consistent.

Most parts are usually fine for water soluable fluxes but there are some ic packages that had trouble, and they were installed after. Most parts were not a problem. Automated equipment had driers built in, so it was like magic, put your boards in the basket and daisy fresh at the other side. 

[pickdropper]

Rf is usually ok with no clean, as much as you can generalize rf, but high frequency rf is where the problems are. Might be that they dialed it in with the residue in place, and if automated should be consistent.

Most parts are usually fine for water soluable fluxes but there are some ic packages that had trouble, and they were installed after. Most parts were not a problem. Automated equipment had driers built in, so it was like magic, put your boards in the basket and daisy fresh at the other side. 

The board I am dealing with is 2.4GHz.  It is sensitive to an awful lot of things.  :-)

[wgc]

Well, if you have issues with resistors "changing" values during use, try cleaning the flux off.  Might be someone trying to save some $$ at the board house by spec'ing no clean and not knowing any better.  Good luck!

[pickdropper]

Well, if you have issues with resistors "changing" values during use, try cleaning the flux off.  Might be someone trying to save some $$ at the board house by spec'ing no clean and not knowing any better.  Good luck!

Thanks. :-)

In this case, it was the circuit designer that specified No Clean / No Wash.  Despite the instructions, the board house kept washing the boards; current habits die hard, apparently.

We finally got them sorted out. 

[m-Kresol]

Hey guys,
as I was finishing up my octaver last night, I scrubbed my board with a soft toothbrush and isopropanol (>98%). That did the trick and removed any solder flux on my board. Unfortunately it also started to dissolve the plastic of the pcb!! Now it looks crappier than before. At least I realised in time.
However, the lesson to be learned here: Go and buy some flux remover instead of using isopropanol.
I should run a mass spec of commercial flux remover, I really want to know which solvent it is, since iPrOH is a rather unaggressive solvent and a soft cleaning agent. Gotta find a cheap way around it with something in the lab

[muddyfox]

Interesting. Was it a FR-4 board?

I tried some 99% IPA on my smd build and while it didn't remove 100% of the flux residue (didn't even use flux pen, only what's inside the solder wire) it did start eating away on SS12 diode markings. With them being chinese I'm not really surprised but kinda makes you wonder...

[pickdropper]

Hey guys,
as I was finishing up my octaver last night, I scrubbed my board with a soft toothbrush and isopropanol (>98%). That did the trick and removed any solder flux on my board. Unfortunately it also started to dissolve the plastic of the pcb!! Now it looks crappier than before. At least I realised in time.
However, the lesson to be learned here: Go and buy some flux remover instead of using isopropanol.
I should run a mass spec of commercial flux remover, I really want to know which solvent it is, since iPrOH is a rather unaggressive solvent and a soft cleaning agent. Gotta find a cheap way around it with something in the lab

Hmm, that's interesting.  How stiff of a toothbrush was it?

I prefer Flux Remover, but I use isopropanol all the time and generally don't have that issue.  Was this an etched board or a fabbed board?  And do you know where it was fabbed?  I have seen some boards with really poor quality solder masks.

[RobA]

...
However, the lesson to be learned here: Go and buy some flux remover instead of using isopropanol.
I should run a mass spec of commercial flux remover, I really want to know which solvent it is, since iPrOH is a rather unaggressive solvent and a soft cleaning agent. Gotta find a cheap way around it with something in the lab

The MSDS sheets for these should let you know what's in them. I just grabbed the sheets from the manufacturer's websites for the first couple that came up on Mouser. The links are below. They are pretty different from each other, so it would seem it depends on which one you are using.

http://www.techspray.com/descriptions/document/1631_us_eng_msds.pdf
http://www.mgchemicals.com/downloads/msds/english/sds-4140-l.pdf

I like to use no-clean flux and the AIM no clean glow core solders. The only time I worry about it is if I've needed to use some solder paste for an SMD part and then I just clean the area with a cotton swab dipped in vodka -- works pretty well and I haven't had any issues.

[rullywowr]

I agree. Since I switched to no clean flux pen and no clean solder (Kester 251) I haven't had much trouble. I have also had good results using non-chlorinated brake cleaner as an alternative to expensive flux remover. I would suggest testing on other junk parts to ensure this won't melt your PCB or components.

[muddyfox]

Kester 251? I only see 245 and 275 as no-clean?

[RobA]

Oops, I didn't mean solder paste -- I haven't tried that yet. I meant flux paste, which I have a syringe full of and it helps sometimes with annoying parts that want to move too much (like every time I move). It's no clean too, but there is usually just too much of it left to leave on the board. So, I do the vodka thing with that.

I ended up needing to use some vodka yesterday to clean up a little breakout (SchmartBoard) board for an SC-70 6 pin part. The thing is so small that it wanted to fly away when I brought the tweezers close to it. So,  I had to use the flux paste to keep it in place.

[stevie1556]

I use a flux cored 60/40 solder. It's 0.7mm so need to be careful with how much you use but it works great!

I put a small amout of solder on a pad, place the component and heat the solder and component.  Then just solder the other side as normal. There is a good youtube video with this technique, I'll post it later!

Sent from my thumbs using Tapatalk!

[rullywowr]

Kester 251? I only see 245 and 275 as no-clean?

Yep.  Kester 50/251 in a 63/73 Pb combination 0.031" diameter I got off eBay for $20 shipped.  It is about 5 years old (and subsequently past it's certified 'fresh' date) but works great.  I recently switched from the old standby "44' (yellow labeled rosin) to this.  I also got a Kester 952 no clean flux pen from Mouser to go with it.  I took my old 44 solder and rosin pen and put them in a bag for a rainy day to avoid grabbing the sticky stuff by accident.

What I found about "no-clean"
1)  I like the way it doesn't leave a gooey mess on the board
2)  The aroma isn't quite as delicious as the old 44   
3)  Takes a little bit more even heating and fluxing the board helps with this to get a nice shiny joint

Overall, I dig the "no-clean" stuff.  Makes a great finished joint and no worries about the gooey mess left over after.  It's really a misnomer..."no-clean" because many PCB assembly houses actually still do clean the "no-clean" solder - ironic isn't it?  I like the fact it is just a clear residue and doesn't get all sticky.