Cleaning PCB-- Is it Necessary?

[BadIdeas]

So I was modding a pedal earlier today and I realized that just about every time I do, the solder doesn't seem to behave right. I had no trouble with my TB FX loop that I just built (my first "from scratch" project) but with manufactured pedals, the solder seems dirty or oxidized or something. It sort of just moves around and my solder pump doesn't suck it up real well. The pedals I have worked on are an Ibanez TS9-DX and a Danelectro Surf'n'Turf (which I ruined... noobage). I tore a couple solder pads off the TS9, but "fixed" it by soldering the leads of the new components together. The result sounded great when all was said and done.

Anyway, my question was whether you customarily clean your PCBs before working on them, how you do so, and what products you recommend and from where.

[clamup1]

yes, the solder sticks better and the ink dosent run and short out another pad. i dont rem what its called but some kind of paint stripper

[nbabmf]

You're getting oxidation on the traces.  Use a Scotch-brite pad to scuff them up a bit and the flux in your solder will work the rest.

[defaced]

Part of it is the manufactured pedals probably use lead free solder (if they're newer this is more likely) and if you're not adding new solder, you don't have any rosin on the joint.  Both of these, lead free solder and no rosin, will kill the wetting action of the solder.  Start by buying some rosin, or get in the habit of adding more new solder in the processes of removing the old part. 

[Mark Hammer]

1) Flux rosin can look remarkably similar to protective coating on commercial boards.  One is responsive to heat, the other isn't.

2) Your scenario is precisely why I make a point of tinning all traces and pads on any boards I make for myself.  Much easier to do post-build mods and add-ons when not dealing with tarnished traces.

[BadIdeas]

Okay, so ALWAYS add new solder to remove a part, and add Scotch-Brite to the shopping list. No fancy chemical solutions or anything? Sounds easy enough, thanks guys!

[BadIdeas]

Thread... REVIVE!
Alright, so I used Scotch-Brite to scuff up the pads and added more solder to the joints. The solder seemed to behave much better on the last mod project, but I am still having some trouble. Whether using a desolder pump or wick, I can't seem to remove enough solder to let the components come out. It doesn't seem to take much to hold on. It is a double-sided board, so maybe there is some solder on the other side that I cannot see or access, as some of the components were things like board-mount pots, wire connectors, and a right-angle rotary switch with 10 pins, though I was expecting a SPDT. 
I ended up ripping off a pad from the stomp PCB trying to detach wire connectors with 3 pins each, and there are several more, so I don't want to ruin anything more important, and I don't have anyone (like friends) to physically do the work with me, so I'm nervous about proceeding until I can be confident in my ability to desolder correctly.

Does anyone have any more advice? Maybe share your experience from desoldering in your noob days?
Inconsequentially, does (Pb) on the PCB indicate lead free solder?

BTW, the project this time was putting a Dano Cool Cat tremolo inside a wah enclosure I scored on eBay with a toggle for manual/treadle rate control. Though discouraged to some degree, I am only more determined to start making effects from scratch, and hopefully then have more success.
Cheers!

[Ronsonic]

The through plated holes on a DS board can be tough, especially if the hole is barely large enough for the component lead. With automated placement getting more precise and solder costing money that's been the trend, holes too small to work with.

Powered solder suckers are the way to go if you've got the tool budget, Hakko is pretty well the industry standard. Lots of Asian knock-offs. Oh so easy.

Alternatives:

Solder sucker from the other side of the board from the iron. Heat one side suck from the other.

Or, or and

Add a touch of fresh solder and then wick it out.

Cover all legs of the thing to be removed with big blobs of molten solder and extract the device while all applying heat and keeping all molten. THen use wick or sucker to clear holes.

Clip the leads off the device, add a touch of solder and heat from the solder side while tweezing or sucking out the leg from the component side. Whether to tweeze or suck depends on how long the remaining leg is. Prefer tweezing, component legs will chew up your solder sucker eventually.

Notice that some of this requires manipulating the board while applying heat, eye protection.

[BadIdeas]

Is this what you're talking about?

http://compare.ebay.com/like/380279232709?ltyp=AllFixedPriceItemTypes&var=sbar&rvr_id=174177294635&crlp=1_263602_304662&UA=WVF%3F&GUID=1791300c1270a0366384b674ffc33c6a&itemid=380279232709&ff4=263602_304662

I think my pump is already chewed up a bit from cleaning the hardened solder out by ramming a tool through the nozzle. If I don't want a powered one, does Hakko make a regular one that is more robust? Is there a better way of cleaning?

Cover all legs of the thing to be removed with big blobs of molten solder and extract the device while all applying heat and keeping all molten. THen use wick or sucker to clear holes.

That worked with the pots OK, the 10-pin DIP rotary switch was a bit more difficult. I actually ended up ripping a few pins out of the switch and having to remove them from the board individually. For some reason, the solder pads where the wire connectors connected to the stomp PCB didn't hold up. I probably was not patient enough.

I am in the habit of wearing eye protection; thanks for watching out for my baby greens. 

[Paul Marossy]

I have much better success using a good quality desoldering braid on those hard to desolder commercial pedals.

[Mark Hammer]

Desoldering braid is wonderful.  Just remember that the same oxygen and "finger juice" that tarnishes exposed copper board also tarnishes desolder braid.  So do your best to keep it clean, and consider a bit of liquid flux applied to the braid to help it overcome its own naturally-occurring tarnish.

[BadIdeas]

I keep a braid and a pump handy when I am working. I can't speak for the quality of either one, though there was an "economy" pump and a "quality" pump at the store I bought them from. I am pretty sure I went with the quality model. I've gotten better at keeping a steady hand with the pump, but am still a bit shaky with the braid. Come to think of it, maybe my hand is more steady because the spring is worn out?
Anyways, can you link me to a specific flux? How do I apply it?

[jkokura]

Desoldering braid is wonderful.  Just remember that the same oxygen and "finger juice" that tarnishes exposed copper board also tarnishes desolder braid.  So do your best to keep it clean, and consider a bit of liquid flux applied to the braid to help it overcome its own naturally-occurring tarnish.

+1

I use some liquid flux and desoldering braid for all my part removal.

jacob

[Ronsonic]

Is this what you're talking about?

http://compare.ebay.com/like/380279232709?ltyp=AllFixedPriceItemTypes&var=sbar&rvr_id=174177294635&crlp=1_263602_304662&UA=WVF%3F&GUID=1791300c1270a0366384b674ffc33c6a&itemid=380279232709&ff4=263602_304662

More like this. http://www.amazon.com/Hakko-Desoldering-Kit-808-Gun/dp/B000ARPULW

That gadget you linked is not likely to be worth bothering with.

I think my pump is already chewed up a bit from cleaning the hardened solder out by ramming a tool through the nozzle. If I don't want a powered one, does Hakko make a regular one that is more robust? Is there a better way of cleaning?

Take it apart? It shouldn't need cleaned that often. Even the cute blue one from Radio Shack should give a year or more service without problem.

Cover all legs of the thing to be removed with big blobs of molten solder and extract the device while all applying heat and keeping all molten. THen use wick or sucker to clear holes.

That worked with the pots OK, the 10-pin DIP rotary switch was a bit more difficult. I actually ended up ripping a few pins out of the switch and having to remove them from the board individually. For some reason, the solder pads where the wire connectors connected to the stomp PCB didn't hold up. I probably was not patient enough.

Clipping pins and removing things piece by piece is valid. Don't be afraid to destroy something to remove it. Real pro's with all the tools in the world often have to resort to that. Take your time, get your zen on and protect the pads and traces. All the rest is optional.

[Paul Marossy]

Clipping pins and removing things piece by piece is valid. Don't be afraid to destroy something to remove it. Real pro's with all the tools in the world often have to resort to that. Take your time, get your zen on and protect the pads and traces. All the rest is optional.

Yeah, I've had to do that many times. Much better to destroy the part that needs replacing than to screw up the PCB, especially if it's a double sided thru hole type.

[Mark Hammer]

can you link me to a specific flux? How do I apply it?

This stuff is fine http://www.mgchemicals.com/products/835.html  I simply keep a box of cotton-tipped applicators on hand, dip one in the flux, and "paint" the braid with it.  I also "paint" boards with it after I have etched and buffed them.  Makes it much easier to tin.

[BadIdeas]

Wow. $178 seems a little overkill. 
As for my little pump, it needs cleaned out every few sucks. It does get annoying getting up every few minutes to drop the solder in the garbage. I guess I could collect it in a little dish and throw it all away when I am done.
As for the switch, the pins were all underneath the part, not sticking out to the side like an IC. Very hard to get to. Same with the pots.
I would assume that a simple cotton ball would work for applying flux to the braid, right? And is one brand of flux likely to be as good as another? I don't think the MG solution Mark suggested is likely to be available nearby. Ordering stuff online is easier for me most of the time. Radio Shack's selection is limited. As is Skagit WatCom, and I don't dig their customer service.
Thanks for all of your advice so far. Keep it comin'.

[Ronsonic]

As for the switch, the pins were all underneath the part, not sticking out to the side like an IC. Very hard to get to. Same with the pots.

If this stuff was easy, anyone could do it. Then where would we cool guys be. Apparently these were worst case sorta parts. Do feel free to use big honking dykes and pliers to chop up and crush and destroy. One of the problems with components like that is that they do soak up a lot of heat from the leads into the internals.

That Hakko I linked is indeed overkill for anyone that isn't doing this daily and professionally. There are cheaper copies for a fraction of the price that will work well for a time.

I'm pretty much out of advice at this point, but offer all the encouragement I've got.

[GroverRock]

Hi,

Anyway, my question was whether you customarily clean your PCBs before working on them, how you do so, and what products you recommend and from where.

I always give my PCBs a couple of light rubs with 400 grit sandpaper, first lengthways,
and then another rub across the board. I find this works very well. I also always clean the leads
on resistors, caps, and lugs on pots and jacks, etc., with the same paper. Not in advance, but when I know I'm going to be soldering them that day. I started this practice a long time ago, and can't recall the last time I had any problems with solder.

Some components  require more care if you use sandpaper, but as long as you stay
aware of static electricity issues, and of how easily pins some can bend, all should be well.
The paper's cheap, available almost anywhere, and lasts a long time.

Hope this helps,
Pete

[BadIdeas]

Hmm, I hadn't thought about static. I think I was going to research ESD protection when I moved on to complete builds, when I will need to store and use ICs and such.
Yesterday, I found an old 3PDT w/ solder lugs, so I decided to give my project another go. I got everything desoldered that I needed to with no discernible problems, but like I said, I don't know about ESD. I also bumped one of the polarized caps with the iron a couple of times, so hopefully it still functions, as it is not a through hole component, so I can't replace it. I won't know until I finish. Right now I'm stuck until I can borrow some tools to get the stubborn treadle pot out. I drilled a hole for one of the new pots without realizing there was no room to mount it without removing the treadle pot.  There is also this strange nub keeping me from getting the threads all the way through...
Nonetheless, I found this attempt much more fruitful and satisfying.
Thanks for all of your help.