Solder Pad Lifting--What To Do?

If it was a 'paper'/srbp pcb ( brown colour and smells funny when hot ) the pads will lift if you look at them wrong ! Avoid leaving the soldering iron on the pcb too long and using a very hot tip temperature.

I'd discard the pad, scrape any solder resist off the track in the area and bend the component lead over onto the track and solder it there.

Graham

If it works and the solder joint was a clean job then leave it alone- it'll probably be fine. If a pad lifts I usually just scrape back some of the coating on the connected track and bend the component leg over onto it and solder.

Don't put epoxy on it, it's unnecessary and will make future repairs difficult.

Dave

"Dave D" wrote in news: snipped-for-privacy@pipex.net:

The proper way to repair it is to set an eyelet,then reinstall the xstr.

eyelet kits are not cheap,though.

--
Jim Yanik
jyanik
at
kua.net

I had the temp at 450F, was using braid and had the iron on the braid a fraction of a second. I am thinking maybe I didn't heat the braid enough and it kind of got stuck to the pad and pulled it off. In addition, that transistor looked like it was a replacement, so it may have had more damage than what I gave it. I replaced two transistors, five out of six ain't bad, I guess...

I plan on leaving alone.

Jim Yanik wrote:

I'd prefer not to have to repeat the repair at a later date. A better solution is to run a wire from the lead at the missing pad to the next node on the trace. I usually use wirewrap wire or perhaps 20-24 gauge.

Using epoxy is a terrible idea.

If I ever need to stick a component down, or lock an adjustment or screw, I just use a tiny amount of standard acrylic nail polish. It dries very quickly, and makes a rigid bond to most materials, which is then easily broken at a later date if need be, by a simple twisting action.

Arfa

Soldering the leg to the track can be as strong or even stronger than the original job, depending on the size of the pad which failed. If it's done properly with enough leg/track area it can last indefinitely. It's sometimes prudent to put a kink in the component leg above the PCB so that if the component is knocked it cannot push through and rip the track off.

In some cases it's possible to feed the component leg through the original hole and bend it over so it reaches the next node. That makes a very neat and satisfactory job.

Indeed. A blob of hot melt adhesive between the component body and one of its neighbours is OK if necessary though. It's very easy to remove if further repairs are necessary.

Dave

I've found that hot melt can peel off pretty easily. Silicone RTV may prove better for this.

Graham

the

it

the

done

sometimes

original

neat

of

prove

Just be careful of the type of RTV used. Some brands will eat the copper.

That is true, though some types are resistant to this.

Dave

I'm talking about using it on the component side btw.

Graham

I did a little more work today and lifted yet another pad out of about

7 or 8 solder joints. I am a beginner, but is this a very common occurance in soldering work? I am using braid on the joints (they don't have alot of solder, usually single componenet lead), 450F (using Weller WESD51), and am placing the tip onto the braid for a second or less at a time, letting cool for 10 seconds or so before going back and wicking more solder.

The unit I am working on is one of the brown boards mentioned, in an old HK 330A receiver ('60s). I notice that throughout the board, the solderer not only soldered at the pads, but spread it out onto the trace for a bit, did it quite often. Why is this? It also seems that it is quite easy to add solder and have it follow the trace, I tacked down a lead onto the trace of the pad that lifted--worked well, actually--and there wasn't any spillover. What is at work here, some kind of wicking action? I am also brushing on rosin paste onto the areas to be soldered and am using rosin core solder. I'm finding that the solder is hard to place at first when there is rosin on the pad, perhaps I am using too much? I'm finding that doing a good solder job is a bit harder than one would imagine...

Pooh Bear wrote:

I never used the braid but I use a solder sucker . Started out with the squeeze bulb and then went to the one that has a plunger you push in and when the solder gets hot you mash a button and the plunger comes up and sucks out the solder.

Stop putting the paste on the areas to be soldered and just use the rosin core solder.

Where did you learn to solder ? Not that I am trying to break bad on you, but I don't recall seeing anywhere that states to put the paste on electronic work. Well, maybe on large areas like making shields but not component leads.

He must have learned to solder about 90 years ago.

In my humble opinion, based on over 40 years of soldering, 450 deg is too hot for standard leaded solder. A typical workshop workhorse iron, the Weller PCT magnastat controlled station, comes with a " 7 " series tip as standard. This develops approx 370 deg at the tip, and that is plenty for standard solder. It is even just about good enough for the new-fangled lead-free solder on small joints. Even the next tip up, the " 8 " series, only develops 430 deg. Apart from the track to substrate bonding failing, which is very typical of old boards anyway, even without overheating, another downside of a too-hot iron is that the internal flux cores on the solder wire, burn off before they have had time to do their work. You never need to use external flux ( enter Smitty at this point !! ) for ' normal ' soldering work, although I would absolutely recommend the use of liquid flux for surface mount rework. Until you become MUCH more skilled with an iron though, I wouldn't recommend that you have a go at SM ...

There is nothing wrong with desoldering braid for a beginner, but there is a technique to using it. Firstly, you MUST use good quality braid, which is expensive. The cheap stuff that you get at radio rallies and the such, is not good at wicking up solder. It should also be kept in its air-tight container, otherwise its ability to wick solder will deteriorate. You must cut off any length that has been used, or even heated without taking up much solder. Don't use a guage which is too big or small for the job, Typical professional workshop guage is 2mm. Before using the braid apply your iron and some FRESH solder to the joint. New solder flows MUCH easier than old, plus the joint will be pre-heated when you come back a few seconds later with your braid. Don't under-heat the joint when wicking. Place the wick against the side of the joint, then get the iron tip flat against the braid. The joint should melt within about a second, and then another second or so should see the solder come off cleanly. Slide the wick and iron off together, to the side.

Finally, I wonder what shape tip you are using on your iron ? For desoldering work using braid, you need one with a flat end - a small chisel or screwdriver type is ideal. A pointed tip is good for soldering, and OK for use with a desolder pump, but does not have enough thermal inertia for work with braid. Oh yes, nearly forgot, before everyone starts screaming that you can make your own braid. Yes you can, but it's a messy business, and unless you've got lots of time on your hands, not really cost effective for a busy repair shop. Probably OK for the cash-strapped amateur though.

Hope this helps. Stick at it. Like lots of things in life, soldering is a skill that has to be practiced and developed, and you will get better and better over the years. Keep it simple in the early days, and experiment on scrap boards.

Arfa

"Arfa Daily" wrote in news:vqSgg.4834$ snipped-for-privacy@newsfe2-gui.ntli.net:

Centigrade;if you reread his post,he said 450 deg*Fahrenheit*. IMO,that is too LOW,and thus he has to keep the iron on the joint for too long a time,causing the lifted pads. Solder wick is also notorious for needing too much heat and thus lifting pads.

("7 series" tips are "7's" because their temp is 700 degF.)

800 deg Fahrenheit.

--
Jim Yanik
jyanik
at
kua.net

You're quite right Jim, my mistake for not looking closely enough. I didn't imagine for a moment that anyone could be soldering at all at that low temperature, let alone successfully ...

450F is only about 230C. That's only 40 or 50 deg past the basic melting point of 'standard' solder, so nowhere near enough. I would normally be looking for about 330C or 630F at least, and possibly a bit more with a small profile tip. I would guess that this is about what a Weller 7 series bit develops actually at the tip

I agree with Jim looking at it again now, that you might be doing damage to the boards as a result of your iron being too cold rather than hot. That said, old paper substrate boards can still be a bitch to desolder at any temperature, without pads coming off

Arfa

You might try something like the solder sucker from Radio Shack, their p/n 64-2060. It is NOT a replacement for a professional vacuum station but it can be easier (and less damaging) than either braid or separate iron plus a hand-held solder pump.

As Arfa mentions in another reply, it often helps considerably to add a bit of new solder to the joint before using either braid or a sucker. With the sucker, you want to quickly liquefy the mass and pull it up as a single droplet rather than heat & suck, heat & suck, ... a sparsely soldered joint.

--
Rich Webb   Norfolk, VA