[bg4533]

After building a few CMOYs, a Mint and a Pimeta I think I have learned to solder fairly well. I have tried desoldering a few times and I find it to be rather difficult. I have a desoldering pump and desoldering braid, but both have their weaknesses. Yesterday while trying to change an opamp and a few resistors in my Mint I tore off one of the pads for the opamp and pulled out one of the pads for resistors. Needless to say, I think i am just going to start over with a new Mint.

So, the problem I have for both resistors and SOIC chips is that both sides really need to be freed up for the part to move. What is the trick here?

This question is of particular interest to me right now because I want to replace or remove the opamp on my EMU 1212M and I don't really want to make a $200 mistake.

 

[jnewman]

The best thing you can do is practice and learn to use the braid and pump to get ALL the solder off - you don't, as you've found out, want to have to pull hard to get things off.

 

[djwkjp]

look thru the thread about modifying the toshiba 3950/3960 in this forum. there are a few good tips in there about how to get those soic chips off the board.
hope it helps
dan

 

[Archeopteryx]

Take a look at http://www.chipquick.com/ for smd removal. I have seen this sold at my local electronics store (Fry's) so you may not have to mail order it.

 

[nleahcim]

For removing surface mount chips, if they're two sided, I cover one entire side of pins in moltent solder and with a jewelers screwdriver I lift up the chip about a mm or so. Then I use solder wick to remove all that excess solder on that side, leaving one side free. Then I do the same thing to the other side - remove excess solder - and I'm done. Quick and easy. But the important thing is to be very fast - you don't want that hot solder on there for too long, otherwise the chip can get damaged.

 

[randytsuch]

For removing chips, I cut off all the leads, then just remove the little pieces of leg that is left. I have seen some people say you can lift pads like this, but I have not had a problem yet, but use a good cutter.

For resistors and caps, I use two irons, to heat up both sides at once.

Randy

 

[DaKi][er]

removing soic packages, i put a flat blade under one side and applying a little pressure then heat up all the pins down that side till they all come off being careful not to bend it too far as the other sides legs will bend, grab some tweezers and grab the chip and heat up the other side of pins and pull it off

 

[MisterX]

Depends on what SOIC chip it is..... for removing a single chip from an unpopulated board I bust out a piece of window screen and put it over a burner on the top of my electric stove.
Then put a cooling rack over the burner.
Make a small puddle of flux around the chip....Turn on the stove and set the board on the rack.
The chip will drop right off and the screen will catch it so it doesn't get incinerated on the burner. Needless to say this method takes a lot of practice to get down but it works extremely will for removing opamps from Browndog adapters (you don't lift the pads or the traces)
For populated boards I just use the flat wide tip for my Metcal soldering station (it will heat every leg on one side of the chip at a time) and lift each side of the chip as the solder flows. (the same tip makes removing thru hole parts a breeze)
One of these days I may but the rework tweezers for the station but they are very expensive

If I am already working with something then the big blob of solder trick works pretty well..... You just have to be careful not to lift the traces off the board.

There was some talk on another forum that the Radio Shack desoldering iron works very well as a hot air tool if you add an aquarium pump to it.
This would be a very slick and budget friendly solution if it works as stated..... looks like I have a project for this weekend after all.

 

[tkerby]

Use a diy blow torch with a small nozzle and heat. Cover components that you dont want to remove with heatproof tape. This is usually a thin orange or blue mylar like tape. The chip will just slide off when pushed with tweezers

 

[gaboo]

Quote:

Originally Posted by Archeopteryx Take a look at http://www.chipquick.com/ for smd removal. I have seen this sold at my local electronics store (Fry's) so you may not have to mail order it.

"Removes QFP's, PLCC's, SOIC's, and chip components under 300 degrees Fahrenheit." I think most SMD stuff is soldered at 300C not F. So this device won't remove much.

 

[Archeopteryx]

Quote:

Originally Posted by gaboo "Removes QFP's, PLCC's, SOIC's, and chip components under 300 degrees Fahrenheit." I think most SMD stuff is soldered at 300C not F. So this device won't remove much.

The idea is that the chipquick alloy melts at low temperatures and when molten dissolves the solder on the smt device, allowing the solder / chipquick mixture to be molten at 300F, lower than the melting point of the solder on the surrounding parts.

 

[beamrider]

Quote:

Originally Posted by Archeopteryx Take a look at http://www.chipquick.com/ for smd removal. I have seen this sold at my local electronics store (Fry's) so you may not have to mail order it.

When everything else fails, this is the answer. Works like a charm.

 

[gaboo]

Quote:

Originally Posted by Archeopteryx The idea is that the chipquick alloy melts at low temperatures and when molten dissolves the solder on the smt device, allowing the solder / chipquick mixture to be molten at 300F, lower than the melting point of the solder on the surrounding parts.

So, it eats the solder through a chemical reaction. Ingenious...

 

[tangent]

I use a couple of methods:

1. The "lots of solder" method mentioned previously, which lets your iron heat up an entire side of the chip at once. This works best on crowded boards, where you can't use the next method.

2. Lay the full iron tip alongside one side of the chip, then quickly move to the other side. If you're quick enough, a couple of moves will allow the chip to slide right off the pads. This works best with small parts, where you have room to get the iron tip to lay down sideways on the board.

As for lifting pads, that happens when you use too much force. It's best to not apply force until the solder is melted. You can go ahead and slide your pry tool or grab with your pliers before heating the joint, but don't pull or pry until you can see the solder melting.