[SOLVED] How to Remove Connectors from Double-Sided Board

[niconiconi]

Today, I need to isolate a pin from PCB and probe it. The pin is surrounded by ground planes on both sides, it would take years to cut the trace, so I drilled a hole around the pin destructively. Unfortunately, I broke the pin in this process. Not a big deal, simply remove and replace the SATA connector would be good, but here comes the headache.

Despite playing with electronics for years, I never learned to remove connectors from double-sided board with plated through-hole. The usual process of desolder: (1) clean, (2) flux the board, (3) heat it with an iron, (4) add fresh solder to reflow, (5) remove the solder with (a) a desolder wick, (b) a desolder pump, simply doesn't work for me.

My experience is basically: first of all, the solder joints are pretty oxidated. Touching the joint with an iron simply won't have any reaction whatsoever regardless of whether there's any flux, so adding fresh solder is mandatory, all right. However, even after adding solder, usually only the top part of the through-hole would be able to reflow, from time to time, the solder inside the plated hole doesn't get a reflow. Sometimes it's badly oxidated and doesn't conduct heat well, and other times, even if you manage to get a reflow inside, it's still out of reach of a desolder pump, applying a desolder wick / pump would only remove the top part, even worse, a incomplete desolder may push the solder deeper into the PTH or to the other side of the board. An exercise in frustration! For smaller parts like capacitors or 8-pin DIP, usually the part eventually comes out, but for connectors, repeat it a few times, the board would be destroyed.

What is the correct way to remove it?

[Ysjoelfir]

The best advice I can give to you is: use a proper desoldering iron. Not one of those cold sucking pumps.
Than: Apply fresh solder, flip the board over so that the solder wants to flow into your desoldering tool, heat thoroughly with the desoldering iron, heat a little bit longer than you usually would and suck as hard and fast as you or your tool can.
Works for me 9 out of 10 times, if it doesn't: Repeat.

[KrudyZ]

In your particular case, you have plenty of access to the connector.
Since it is a one off situation, assuming you don't have a batch of these to rework, I would simply go ahead and cut the connector housing to pieces with side cutters.
Once you are down to single pins, taking them out one by one is easy.
Try not to put too much pull strain on the pins during cutting and desoldering, so you won't delaminate any of the traces.

[JustMeHere]

A preheater would help.  I don't have one, but I believe it would make this easy.

Hot air is how I would do this.  Sounds a bit crude, but clip something heavy on the connector. (I use locking needle nose.)  Heat the other side with 350 C and a fairly moderate air flow.    I let the weight of the pliers pull down on the connector (gravity) while I heat from the other side. 

A pillow covered by a towel catches the pliers as they fall.

[niconiconi]

A preheater would help.  I don't have one, but I believe it would make this easy.

Hot air is how I would do this.  Sounds a bit crude, but clip something heavy on the connector. (I use locking needle nose.)  Heat the other side with 350 C and a fairly moderate air flow.    I let the weight of the pliers pull down on the connector (gravity) while I heat from the other side. 

A pillow covered by a towel catches the pliers as they fall.

Thanks for the tip. I've been using this technique previously, but now avoid doing it if I can.

It works sometimes, but in my experience, is not foolproof. You'll have difficulties if there is a ground fill or ground plane nearby that dissipates the (already limited) heat from the hot air, and forces you to apply extra temperature or time. Also, overheating the board, even when there is no obvious superficial damage, can silently break small vias and separating the layers. I learned it the hard way...(In one attempt, I also damaged the solder joints of a BGA on a daughterboard in one attempt of removing it from the main board.)

Anyway, I think this technique is useful for removing dumb or "don't care" parts like connectors on areas of the board without delicate traces (I once used it to remove a power transistor in an amplifier board that has solder stuck inside), but at this point, I don't recommend doing it without a preheater (I think I need to get one now  ).

[niconiconi]

The best advice I can give to you is: use a proper desoldering iron. Not one of those cold sucking pumps.
Than: Apply fresh solder, flip the board over so that the solder wants to flow into your desoldering tool, heat thoroughly with the desoldering iron, heat a little bit longer than you usually would and suck as hard and fast as you or your tool can.
Works for me 9 out of 10 times, if it doesn't: Repeat.

I checked my copy of Quality Hand Soldering and Circuit Board Repair (6th edition) by H. (Ted) Smith, the book agrees with you, and said a desoldering iron with powered vaccum is essential for general THT rework. In page 90, it even has a picture that shows why using a desolder pump or wick is a bad idea on double-sided board (remaining soldering will stuck inside the PTH). Although it's not necessary for this single case, I have ordered one for the future work. A part has been damaged on the way to me, and I'm still waiting for the replacement from the vendor. 

[niconiconi]

In your particular case, you have plenty of access to the connector.
Since it is a one off situation, assuming you don't have a batch of these to rework, I would simply go ahead and cut the connector housing to pieces with side cutters.
Once you are down to single pins, taking them out one by one is easy.
Try not to put too much pull strain on the pins during cutting and desoldering, so you won't delaminate any of the traces.

I agree  . I'm persuaded that destructive removal is the best one-off solution in this case. This 22-pin SATA combo connector is held on the board by two supporting legs on the left and right. Once both sides are cracked open, it's easy to cut and break all the pins.

I'll try doing it over the weekend. Anyway, I think my problem is solved at this point. Thanks for all the recommendations. 

[Mechatrommer]

1) heat gun with patience. slide heat until you can lift the connector from one side.
2) make a big blob of solder connecting all pins, drag solder to ensure fluidity on all points of the blob, and again lift the connector from one side and... patience.
3) low melt solder on (2) much easier
4) destroy the connector, clean and suck out left over, replace with new connector.
5) infrared pcb/reball repair rig in ebay.

[JustMeHere]

I forgot about ChipQuick.