Replacing Large PCB Pin-Headers/Eurocard?

[steeltoe]

Is this realistically possible, without destroying the board? I would like to replace an awkward right-angle 96pin eurocard header with a straight version so I can avoid a bunch of noise-prone cabling. But how would one go about such a delicate operation (in the surgical sense)? De-soldering seems like it could save the header, but would likely destroy the pads/traces on the board.

The only thing I can think of is to cut away the header, and drill new pin-holes through the center of the old conductors very carefully on a mill drill (probably even use shorty drills or endmills). At that point I'm reasonably confident in my ability to tack the new header on without ruining anything.

Advice from anyone who's "been there" and had to remove/replace a large multi-pin soldered item without destroying the board?

 

[(*steve*)]

A picture would help, but a vacuum desoldering station will probably do what you want.

 

[kellys_eye]

Cutting the pins from the 90 degree connector then desoldering them individually seems the easier way. I'd use a dremel tool and slice the connector as close to the board as possible - you could use a hacksaw too if you were careful - and I mean careful!

 

[steeltoe]

My header is just like the large white one on the right side of this picture;

Three rows of 32 pins, about 1/16" apart from each other; pretty snug. Now, I'm not particularly familiar with desoldering techniques, I've just used those wicks a few times (which sort of worked). Wouldn't removal of the solder by melting it away disrupt the connection between the pin-hole/sleeve and copper traces (not familiar with that aspect of PCB construction)? Any recommendations on soldering irons that won't damage the board while I'm freeing the pins? My current pistol-style high-wattage tool is not really meant for delicate work.

Reading up on vacuum desoldering it seems the procedure is;
-Clean the exposed terminal
-I'd likely cut away all but the pin so I can manipulate them independently with forceps from the soldered side
-Apply solder to the board to form a raised bubble
-Suck the bubble up & away with the solder sucker to remove most of it
-Wiggle the pin loose, melting the remaining solder as needed to do so
-Clean the empty terminal (and I suppose clean it of residual solder with a small drill bit/reamer)
-Rinse & repeat (ninety five times...I imagine frequent breaks are a must)

The other tactic I thought could maybe work since I'm not salvaging the pin header, is to cut the block away leaving a bunch of exposed pins opposite the soldered side of the board, hang a pair of locking forceps on the wire and let gravity pull it through once a touch from the soldering iron to the pin melts the stuff. I think this would leave more solder behind, but would apply heat to the board for a shorter duration (and I could still drill/ream out the tubes carefully afterward so the new contacts fit through). I suppose this way also avoids the need for powered cutting tools (vibration & metal filings) to be applied to the board.

TCB

 

[(*steve*)]

Vacuum soldering works like this:

1. Heat up the joint and suck out the solder.
2. Move to the next pin.
3. When all pins have been desoldered, turn the board over and the part falls out.

Of course it isn't always this easy, but doing things like desoldering 64 pin chips is pretty easy.

Cutting the pins and desoldering them one by one is far easier, but having a vacuum desoldering station means you can clean out the holes so you can insert a new part.

 

[steeltoe]

"Easy," huh? I like the sound of that! Sounds like something I could actually do, lol. Again, my last experience was desoldering Nixie tubes with an iron & wick, and the process was...painful. I wasn't trying to save that board, but I do remember a number of the PCB solder-tubes were yanked out along with the Nixie contacts, and I can't afford to have that happen on this board. It sounds like these sucker tools really improve that side of things (sure looks that way from a few videos I've watched, too)

Should I be wary of the heated syringe style tools, are there any advantages to the two handed method of iron & sucker? This seems like the kind of job where the right tools make a huge difference.

Thanks a ton for the advice (and the positive reinforcement, even if not intended; I started out convinced this could not be done without destroying the board)

 

[(*steve*)]

I use the type where you heat the joint up, pull a trigger, and a vacuum pump sucks out all of the solder.

The closer the fit of the wire in the hole, the harder it is. It is still very possible to damage the board, and even with the best technique there's always a couple of joints that have to be done more than once to get all the solder out

As a guess, you're looking at (at least) $200 for a cheap vacuum soldering station (actually, maybe a bit less).

If you get something like that, the first thing you need to do is to modify it so it doesn't block up after the first 2 or 3 desoldered joints. Get one of those metal swarf "solder sponges" and place a loose wad of this into the solder chamber in place of the spring. This will catch and cool the solder before it coats the filter at the end.

 

[kellys_eye]

If you can justify the expense of a solder pump station then do it. But simply cutting the leads, desoldering them (apply heat until they loosen, then pull) then using solder wick with added liquid flux will remove the remaining solder from the holes and leave a nice clean result. All the pro's clean up their desoldering jobs using solder wick and flux....

The main issue is the application of too much heat which may cause the pcb tracks to lift and/or through-hole plating to come out. On double-sided boards (yours by the look of it) such faults can be repaired but it's always best to avoid creating more problems that you solve.

As to your original issue (noise prone cabling), is this a genuine and specific issue? and could it be fixed with screening, rerouting or the use of ferrite cores over the offending cables?

 

[(*steve*)]

I agree 100%

If you don't want to keep the part your removing intact, cutting the leads and pulling them out one by one is a better option.

It may not be as showy as turning the board over and the part falling out, but it is likely to be faster, especially for things with thick, rigid pins.

Although, a vacuum pump is a quicker and easier way of cleaning up the holes. But if you have good solder wick, the difference is smaller.

If you have trouble getting solder out of plated holes, chances are you don't have good solder wick. Most of the stuff that comes out of China is complete rubbish -- well, the stuff on eBay is anyway.

 

[kellys_eye]

If you have trouble getting solder out of plated holes, chances are you don't have good solder wick. Most of the stuff that comes out of China is complete rubbish -- well, the stuff on eBay is anyway.

Absolutely! But the key is to have good liquid flux - I use RMA (rosin mildly activated) and clean up afterwards with IPA (isopropylalcohol) BOTH of which items a decent workshop should always have a supply of.

Although the 'good' solder wicks are supposed to be flux impregnated I find they dry out too readily and the dust falls off - a squirt of RMA flux and the stuff hoovers up solder like it's no-ones business.

 

[Arouse1973]

Yep, I agree with the Scottish bloke
Adam

 

[kellys_eye]

Yep, I agree with the Scottish bloke
Adam

Yorkshire man actually

 

[Arouse1973]

LOL, close enough