Removing relay without damaging pcb (plated through holes)

If using a desolder tool and solder braid still leaves it stuck it's often best to carefully wreck the component so you can treat each pin individually.

--
*Why is it that doctors call what they do "practice"?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Make up a pyramidal truncated frustrum (Google) out of 4 pieces of tin- plate, wired together. Mask off that area around the relay, with the frustrum temporarily wired to the board. Mount board firmly in vice, near the relay. Pull and wriggle the relay when you apply heat from a hot-air gun directed into the frustrum. If you don't believe it will work try the technique with plated thru comps on a scrap board first. The hotter the air and quicker you are the better, if board starts to discolour there is probably some other mechanical restraint.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

There is only one way: chop the relay up until you can get to each pin, and desolder those individually.

I however would open the relay and file the contacts, far easier option.

NT

gun

As it happens, the last week I've been working on industrial boards with plated-through soldering. Thick board so only tips of IC leads protrude, very thin signal traces, traces to tiny pads on both sides of boards of same pin in some cases and plated vias under ICs as well. I know if i'd used "proper " vacuum assist desolder or butcher-and-remove single pins , many of those traces/pads would have dislodged. I had to sharpen the points of my large adapted circlip pliers to get the extra purchase on the ends of these 14,16, and 28 pin ICs. Not one dislodged track using a paint-strip hot-air gun. Next time i'll have to take some before and after pics for the doubting thomases.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

That's the way I'd do it.

That's the way I've done it.

on

I would just leave it as it is rather than knacker the board

Any recommendations on how to "chop up" the relay? Its a sealed plastic type.

Are the pins smaller than the plated through holes. or are they a tight fit? If there is any free space you can remove the solder, then heat the pin till the solder melts and gently bend it loose from the wall of the plate through hole. I've done it that way for decades, but you should practice on a scrap board first.

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Service to my country? Been there, Done that, and I've got my DD214 to
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Member of DAV #85.

Michael A. Terrell
Central Florida

Sharp cutters like these:

Cut into it from the top and keep cutting stuff away until just the pins are left. Be careful cutting away the plastic bottom that you don't scratch through traces or otherwise accidentally damage the board.

If you have a *good* desoldering tool (with a vane pump etc.) it may be possible to suck almost all the solder out of the holes so they break away when wiggled without damaging the plated-through holes, but it's not always possible, and it runs more risk even with good tools and even if you have just cleaned the tool out.

I've used a Dremel tool to remove relays, as well as other components, by cutting them to pieces, carefully, of course. Then I unsolder one pin at a time. Unless you need to do failure analysis on the bad part.

Al

Which bit do you use? A grinder or a saw bit

Cutting off the relay is the hard bit, as many have quite hefty bits of steel in them. A cutting wheel in a die grinder (aka dremel) works, but can be slow.

NT

My own method would be a good hot iron, plenty of solder braid and a lot of patience.

Ron(UK)

I've often found that in a pinch, you can wick the solder out, re-fill the holes with new solder, re wick the holes. Sometimes the re-filling process can reflow the whole joint instead of wicking out the top half and the bottom never gets hot enough. Of course, not perfect, and should be done on a scrap board.

Steve

That`s true. One of the things novices do wrong is to wick off most of the solder, but leave a little behind deep in the hole, that wont be drawn up into the solder braid. Then they get impatient and try to rip the component out damaging the board in the process.

There needs to be enough solder to easily wick up into the braid, and the iron need to be hot enough to melt all the solder in the joint through the braid or there`s a chance that pulling the braid away takes some of the pad with it.

There`s as much an art to desoldering as there is to soldering. (IMO)

Ron(UK)

The solder used for wave soldering is 80/20 and has a higher melting temperature. By removing what solder you can, then adding fresh 60/40 you move the melting point to somewhere in between, which then can be either vacuum desoldered or removed with solder wick and a drop of liquid rosin flux.

80/20 is used for wave soldering, because it has a very narrow temperature range where it is in a plastic state. this reduces cold solder joints, by not giving the leads a chance to move while the solder passes through this state.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Really? I want proof. If 63/37 is the only solder used, please explain to everyone WHY there are so many different solder alloys sold for electronics. I have NEVER seen a wave solder machine filled with eutectic solder. 80/20 was used in all the wave solder machines I've seen because it has a higher melting temperature and goes from liquid to solid almost immediately.

I shouldn't have included the reflow process, because there is too damn many low temp plastics used in SMD components these days. Earlier boards only had the resistors, capacitors and semiconductors reflowed, which could use higher temperature solders. Now there are lots of crappy SMD connectors, pots and relays that require a lot more work to create a workable reflow profile for the oven. Every board design has to be evaluated, and a custom profile created for that assembly. We had over three hundred profiles stored on the Heller oven when I left Microdyne, all sorted by assembly/stock number.

They kept changing the paste solder for reflow, and replaced the two original ovens with the computer controlled Heller so I couldn't keep up with all the variations in alloys, ball sizes and fluxes. It seemed like as soon as we found paste solder that worked right, we couldn't get more of it, and had to start looking again. I know that the solder I used for rework was .015" 60/40.

is a chart of alloys currently available from Kester. They list 13 various tin/lead alloys.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Steve wrote in news: snipped-for-privacy@4ax.com:

maybe use some very low melting point solder like ChipQuik? And a vacuum desoldering tool.

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Jim Yanik
jyanik
at
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