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Really out of my wits as to how to completely remove the remaining solder in the 6 pins (LAT,/OE,CUK,DIN,GND,V+). I would appreciate your advice if you have any relevant experience. front side

back side

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    \$\begingroup\$ Looks like you already did a number on some of those pads. /OE in particular will need patching. Whatever method you choose to remove the rest of the solder, be more careful. \$\endgroup\$ – Unimportant Nov 10 '20 at 20:43
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    \$\begingroup\$ If you don't mind sacrificing the connector, you can cut the pins on the top. Removing the pins one at a time is much easier. \$\endgroup\$ – Mattman944 Nov 10 '20 at 23:00
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    \$\begingroup\$ @Mattman944 I think the OP is referring to the single row of 6 along the bottom, which has already been somewhat mutilated. \$\endgroup\$ – brhans Nov 10 '20 at 23:12
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    \$\begingroup\$ From the photo, it looks like your soldering iron isn't getting enough heat into the solder before extraction, that's what is causing the physical damage. I see large copper areas nearby, those need time to soak up enough heat, otherwise they will pull heat off the area you're reworking, which makes the solder seize up. Too much heat, or too much physical force, will permanently rip the copper foil off of the board. \$\endgroup\$ – MarkU Nov 11 '20 at 0:08
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    \$\begingroup\$ @RussellMcMahon Don't answer questions in the comment section, especially when there's already a perfectly fine answer outlining exactly that procedure. \$\endgroup\$ – pipe Nov 11 '20 at 15:32

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There might be no pad left on some of those pins, looking at the pics. That said, a combination of these will work:

A solder sucker - terrible name but yeah, thats what it does. Make sure to get the silicone tip so that you get good vacuum between the tool and PCB. If you haven't successfully removed the solder, you might want to add more solder to "close" the pad so that the vacuum will work better on the next attempt.

enter image description here

Desoldering wick. It will draw the solder via capillary effect. Use plenty of flux and DON'T rub the pads.

enter image description here

For larger connectors, preheat or hot air might also help.

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  • \$\begingroup\$ What happens if you rub the pads? \$\endgroup\$ – Tashus Nov 11 '20 at 4:42
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    \$\begingroup\$ Pretty sure it's possible to lift the pads off, as solder can be stuck when cold, and the stiff wick may act as leverage to force the heated pads to delaminate. \$\endgroup\$ – crossroad Nov 11 '20 at 5:32
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    \$\begingroup\$ @Tashu The pads come loose under the high heat, the wick scrubs them off and they tend to peel and/or break up. They won't go back down again. \$\endgroup\$ – Guy Inchbald Nov 11 '20 at 10:17
  • \$\begingroup\$ Adding more solder, especially to a failed attempt, is a tip I endorse. But the whole process needs some care: too much heat for too long will cause the pads to loosen, allowing pressure or suction to distort them. It can also work its way up the leg and damage the device. So don't go at it too long without letting things cool in between goes. \$\endgroup\$ – Guy Inchbald Nov 11 '20 at 10:20
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Solder wick is cheap and a good addition to any soldering setup and usually gets the job done. You could also refill the holes with solder and heat one side with the iron while you extract from the other side.

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What usually works is to add some fresh solder. Use the soldering iron tip to remove most of the solder by holding the board vertically, then touching the iron tip (also vertical) below the pad and allow the solder to flow down onto the iron tip.

You should have pads and holes that are filled with solder but not much solder above the pads.

Make sure that the iron tip is well tinned for this next step.

Make sure the circuit board is freely movable. In other words, unplug as many connectors as possible.

Use the iron to heat one pad / hole. Keep the iron tip on the pad as long as necessary for the solder to melt completely. Then quickly rap the end of the board closest to the holes onto your table surface.

The soldier will fly out of the hole onto the table surface.

If the hole is not completely clean, re-solder the hole with a bit of solder. While the solder is still molten, rap the end of the board against the table again.

This works well but you may have to practice a bit to get good at it.

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Since it seems like the question is really just how to remove the remaining solder (presumably so that you can e.g. put a new pin header in there), this works in a pinch:

Support the board above a non-critical surface like a paper towel.

Have a soda straw handy, then apply the hot soldering iron and just enough solder (hopefully flux core) to fully melt the solder that is there.

Then quickly move the soda straw firmly over the hole and forcefully blow.

Solder is usually blown through the hole onto the surface below. Cut the end of the straw square and repeat as needed.

You can clean up the holes on each side as needed with a very clean hot soldering iron tip.

Good luck!

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  • \$\begingroup\$ Intriguing! I will have to try it some time. \$\endgroup\$ – mkeith Nov 11 '20 at 5:10
  • \$\begingroup\$ Sometimes I use a solder-sucker in this way but pressing the button down over the hole instead of releasing it. \$\endgroup\$ – Joe Mann Nov 25 '20 at 14:40
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My experience is that I can rarely get a combination of solder wick and a solder sucker to get the job done if there are more than two or three pins to de-solder. Here I am referring to removing the original component, not just removing the rest of the solder, but I think this information applies to both situations.

I have a hierarchy of measures of increasing efficacy and effort (or expense). First I try number 1, and if that doesn't work, number 2, and if that still doesn't do it, I pull out the 'big guns' of number 3. I don't claim to be a soldering expert, but this is what works for me.

  1. Solder wick / solder sucker
  2. Solder wick / solder sucker + hot air gun to heat the pcb near the component, and of course a regular solder iron.
  3. If neither of those work, then this has ALWAYS gotten the job done for me: Chip Quick SMD Removal Alloy, along with the solder wick and/or solder sucker. Even though it is made for SMD, it has worked well for through-hole components too. It is a very low-temperature solder, which you apply after you have removed as much of the original solder as you can. Because of its low melting point, it gives you much more time before it solidifies, enabling you to work on many pins at once. It will also mix with the old solder and make it easier to remove..it seems to be thicker too and come off more easily (the solder sucker seems particularly effective here). You have to be sure to remove it well afterwards before putting the new component in. It is expensive, but you don't need to use very much of it. Buy it once and keep it around, and it can save you a lot of time and frustration when nothing else works. enter image description here
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I have been somewhat successful using a solder sucker. You have to blob solder in the hole so that the hole is blocked with solder. Put the board in a vice or clamp of some sort. Hold the soldering iron on one side of the hole, and hold the solder sucker directly on top of the hole on the other side of the board. Give the iron time to thoroughly heat up the solder. It must be liquid all the way through. Use flux, too.

Then timing is key. Lift or tilt the iron just a tiny bit a split second before pushing the button on the solder sucker. The sucker can't get the solder out if the iron is blocking the hole. So you have to tilt it or lift it just a bit right before sucking. But if you wait more than a split second, the solder will turn back into a solid and it won't work at all. It is tricky but it can be done.

Just to be clear, if you are holding the solder sucker against the TOP side of the PCB, then the iron should be on the BOTTOM side of the PCB. The nozzle of the sucker should be sealed against the pad around the hole.

After that, I typically put flux on the hole and re-melt the tiny amount of remaining solder to make it tidy. Sometimes this closes up the hole a bit, but usually not, or not completely.

If possible, shove a pin through the hole to mechanically open it up if it is a tight fit.

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Definitely add some solder and with a hot iron, use a solder sucker. Make sure the solder melts all the way through the board. You and then use wick for clean up.

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It's not the answer you are looking for, but a tool like a Hacko FR-301 makes easy work of desoldering.

It might also be helpful the use a hot air gun to get the PCB nice and hot before trying to remove the solder with solder wick or a solder pump.

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I bought a blade soldering tip specifically for this purpose. Makes it safer to remove and install without cleaning up the holes. You need solderwick to clean up those holes and you may need to add more solder before removing it to fully clean the holes.

I find you often need to press a round iron tip into the wick so it depresses into the hole just a bit, but the tip cannot be too small or else the wick will act as a heatsink and not get hot enough. Use the largest tip you can get away with. You may need flux too if you've gone at it multiple times and failed since it is no longer clean and fresh.

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This less formal method can make a useful addition to the methods suggested by others.

Summary: Sharp impact of board with a melted solder blob on it will dislodge the blob. Experience can turn this into a useful method.

  • Hold PCBA in one hand.
  • Add blob of extra solder to pad - this adds to what is there already, but makes it easier to dislodge the whole amount.
  • Heat until nicely liquid while trying to not do so long as to damage pad.
  • Strike PCBA sharply against a solid surface.

The impact will dislodge solder blob largely whole.
This will splatter on impact so do it in an appropriate location.
Experience will show what combination of blob size and impact impulse will best work. Can be remarkably effective.
Practice on something unimportant first.

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For years I patiently wrestled with desoldering braid and solder suckers, rarely with clean results. Nowadays, once the component is removed and I'm trying to clean up the hole of excess solder, I simply use a small hand drill (essentially a screwdriver handle with a drill bit chuck) to ream out the hole. It is shocking how quick and effective this is. It honestly feels like cheating.

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  • \$\begingroup\$ +1 I don't know why this received a downvote. Or why no other upvotes. This does indeed work well. I use a small chuck made for inserting in a larger chuck to allow very small drills to be used - available as an accessory item at low cost. \$\endgroup\$ – Russell McMahon Nov 11 '20 at 18:50

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