De-Soldering Lead-Free Solder PCB joints

[nevetslab]

I've got an Eden WT-800 on the bench with intermittent connections on the front panel PCB. Later generation unit, having the 'properly built' amp modules (if ya wanna call them that) and better constructed front panel board. Once I got the board out and had a look at all the rear panel I/O headers, and all the front panel pots, I kinda wanted to heave. Cold solder joints everywhere on the headers....of course the type that when heated back up, the pins melt the plastic and want to fall over, mis-align, come out.....Methode parts?? Ain't Molex! Gotta have mating connectors installed to keep the pins in place while dealing with the de-solder / re-solder process. Cold solder joints on all the pots, though most of the components flow-soldered look ok.

Right Channel on the Master Volume either has a gritty wiper that won't exercise out, or I have DC on the pot....but hadn't yet determined that. Figured I'd do some board maintenance, and sure looks like it needs it.

Then, I find whoever installed the pots used like 18" of solder----just kept pouring it on...and on....and on....and on. So, no way...absolutely no way to remove it all from the bottom side without lifting the pads. Went to remove a pair of caps in the way to gain access to the 'inside' of the dual-gang pot, and ......my PACE SX-70 DeSoldering Iron was rendered useless. Wouldn't heat up common component lead solder pads. OH GREAT! LEAD-FREE SOLDER!!!

Or.....how to NEVER NEVER EVER EVER EVER EVER ALLOW A DE-SOLDERING IRON TO WORK!! I HATE that C*#P!!! And looking at the headers, my blood pressure shot up.

What is the technique for using a well-maintained PACE De-Soldering Iron and this Lead-Free solder on PCB pads that WILL fail if you crank up the heat to melt the solder? I'm already patching the damage on the Master Volume from their application of 18" worth of lead free solder.

Sometimes, saying yes on a problem child just makes ya wonder what did ya do wrong to deserve this!

[The Dude]

This may sound counter-productive, but I've had the best results by adding some regular solder to the joint first ("non-lead-free"). I have a Pace station also, and usually after adding some "old school solder", you can suck the solder out of the joint. Sometimes, on double sided boards in particular, you have to do this a few times before you can get all of it out of the through hole.

[olddawg]

Have you tried "Chip Quick" and desoldering braid?

[nevetslab]

After cleaning the PACE tip, still leaving the Tip temp @ 750 DEG F and having no success, I resorted to 0.10" wide desoldering braid. That was the only way I could tackle the over-done piles of solder on the pots, and same on the 4mm spaced 0.062" sq I/O headers....using a mating female connector mated to the male header to keep the pins aligned while desoldering and resoldering them.

I haven't yet cranked up the Tip temp to see where the lead-free solder melts down. I got nowhere at 750 DEG F....it just heated the joint without doing anything (apart from heating up the adhesive bond to the PCB).

I too have applied fresh solder to promote heating of the solder joints, as well as with heat from the iron tip added to the desoldering tip in the past, but haven't resorted to that on this board.

What I did see helping out in the solder joint quality since first posting was applying the desoldering braid and sucking some of the cold solder out, leaving a shiny solder joint in place of questionable joints.

I tried again at 800 DEG F on the Pace TIP, still not cooperating, though the tip works fine on a different board, 750 Deg leaded solder...so not an Iron or tip issue.

I didn't get any close-up shots of the horrible I/O header soldering with mounds of dull caked-on solder yesterday prior to de-soldering and re-soldering with Kester 60-40 Type 44 0.031" , but got a couple shots afterwards, compared to Leaded solder on similar PCB-mounted headers:

[Enzo]

The lead free solder is usually not shiny even in a good joint.


To the extend lead-free solder EVER makes a good joint.

[nevetslab]

I should have said 'shinier' than it was. Sucking the solder out of the joints on the I/O pins, as you said, are NEVER shiny. I don't have any Lead-Free solder, still using kester 60/40 0.031" dia type 44. The resultant re-soldering of the lead-free leads (I presume they are) and the residual left-over lead-free solder, it still is dull in appearance. At least looks far better than it was, enough to try again tomorrow.

[Mick Bailey]

Have you tried "Chip Quick" and desoldering braid?

Chip Quik is my favourite for this kind of job - as well as for its intended use of SMD removal. Confusingly, the lead version works better than the lead-free on lead-free boards.

For re-soldering I use a silver-loaded lead-tin alloy also intended for SMD. (Also supplied as a coil packed inside 70s Tektronix 'scopes in case you ever needed to change the DC restorer caps). Very fluid and a lower melting point than regular alloys.

[nevetslab]

In this particular maintenance job, it's all thru-hole work, with most of the problems thus far large-diameter leads (0.062" square headers, PC-mounted pots). I've had this issue before, encountering lead-free solder on wave-soldered PCB's where the Pace DeSoldering tip won't melt the solder on the component leads, as I ran into yesterday. I don't do much SMD work as a rule, but will look into Chip Quick's products.

[olddawg]

In this particular maintenance job, it's all thru-hole work, with most of the problems thus far large-diameter leads (0.062" square headers, PC-mounted pots). I've had this issue before, encountering lead-free solder on wave-soldered PCB's where the Pace DeSoldering tip won't melt the solder on the component leads, as I ran into yesterday. I don't do much SMD work as a rule, but will look into Chip Quick's products.

Most people use too much heat and traces lift because of it. Chipquick allows the solder to stay molten longer at a lower temperature. You must, however, make sure that it is all removed before resoldering. Use braid. It will look factory perfect if you take your time. I have 25+ years experience with reworking multilayered boards. Take your time. Practice on a junk board if possible. Use as low a heat as the Chipquick will permit. And liquid flux. You can always clean up the excess with a little alcohol.

[Enzo]

Insufficient heat will also lift pads. A hot iron will melt the solder faster. Low heat takes a lot longer to melt the solder, all the while cooking the glue under the copper.

[olddawg]

Insufficient heat will also lift pads. A hot iron will melt the solder faster. Low heat takes a lot longer to melt the solder, all the while cooking the glue under the copper.

That is absolutely true Enzo and you are absolutely correct as usual. Under normal repair conditions I prefer using a hot iron and a quick touch. It usually takes a while for a new tech to get the technique down. My point was specifically for the use of ChipQuick which purpose is to significantly lower the melting temp of the solder and allow it to remain fluid for a longer time.

[nevetslab]

From what I've read on line about Chipquick, this certainly does warrant pursing and working thru the leaning curve. Sure get tired of Fender's HotRod series PCB's solder pad's failing if you even get near it with heat!

Thanks!

[Enzo]

Yes, I wasn't disagreeing with you, I just didn;t want a young tech to come away with turning down the heat as the answer to soldering problems.

Chip Quik is great because it alloys with the existing solder to make something that stays molten quite a while (relatively) after removing the iron. You have time to melt along two sides of a small IC and pick up your tool and remove the IC, for example.

[blindboybenton]

I only use leaded solder. Just don't like using leadfree. I got about 5 rolls out of my last firm before they went bankrupt about 3 years ago but i only use them as a standby.
My iron is a Metcal Its not temp controlled but i like it.... i only really use braid. I find you don't damage the tracks as easy. Solder sucker just to clear the large amounts off