CurtPalme.com Home Theater Forum

RVonse · Joined: 09 Mar 2006 Posts: 3152

I am having a real bad time trying to change out a 200 pin IC in my laptop and was wondering how you guys are able to do it. The pins themselves do not actually go into the printed circuit board (which would seem to help) but are just soldered right onto the foil. The main difficulty I have is how to heat all the pins up at the same time? The chip is about 1" square and has around 50 pins on each side.

How do you pro's get these chips out without breaking them or messing up the printed circuit board?

jkruger · Joined: 24 Oct 2007 Posts: 2435 Location: Carlsbad, CA

Special desoldering tools...

**Curt Palme** · Posted: Fri Nov 14, 2008 3:03 pm Post subject:

If it's an Apple, I'd talk to Hammerhead Tech. They have $35K worth of robotic equipment to do it. Generally AFAIK, that's what you need. I personally would not attempt to do this myself.

Talk to Hammerhead anyways, they might be able to do it for you.

lostmandan · Posted: Fri Nov 14, 2008 3:04 pm Post subject:

I have done some limited rework of large chips, and would suggest the following:

Before touching the board with heat, take a few photos of any components that are nearby. I find that there are normally some SMT parts (resistors, caps) near these chips and I have found situations where they have come off when I get overzealous with solderwick Smile

In terms of removal:

Low-melting point solder - I have some low melting point solder that is useful for removing chips because it stays liquid for a short time after the soldering iron is removed. The concept is to connect all of the pins with the solder and allow the chip to 'float' in it. When melted, the chip lifts right off the board. Gentle cleaning with solder wick cleans up the pads for the new device. The operative word is gentle because it is very easy to remove the PCB pads by scrubbing or applying too much heat.

Piano wire - I have also successfully removed chips with a length of very fine piano wire. The concept is to pass the wire behind all of the pins on a side of the package and then, starting on one end of the row, melt the solder on each pin and pull the wire under. This will normally 'spring' the pins enough that they are not making contact with the PCB pads. Once complete, the chip should come off of the board in short order.

Be very careful with the amount of heat applied. The chip may be defective/not worth keeping, but heat can easily delaminate the copper pads from the PCB. If this happens you may be in for a bit of a repair job, if the traces are on the outside of the chip (not underneath).

I hope this helps!

Cheers,
Dan

RVonse · Joined: 09 Mar 2006 Posts: 3152

That piano wire sounds like a neat idea Dan, thanks for sharing.

But where did you buy piano wire?

lostmandan · Posted: Fri Nov 14, 2008 3:35 pm Post subject:

No problem - I read about the technique on a post somewhere online myself.

*laughs* That is a really good question. I think it was something I had around in a box of 'junk'.

Guitar or violin strings would work too I think. The only tricky point would be to make sure the string was made of a metal that does not take solder easily. I am not sure what material the string I have is, but solder does not actually whet to it.

Around here there are a few music stores that sell strings, picks, bows, etc for instruments and I would try there first if I needed to find another string.

Also, I just took a look at the low melting point solder and I don't have a part number/brand on mine. It looks like zeph.com lists a bunch of that sort of thing though. It definitely is not cheap.

Cheers,
Dan

**Curt Palme** · Posted: Fri Nov 14, 2008 3:36 pm Post subject:

Umm, a piano wire store? Duh! Very Happy

It's not really different than a thin guitar string..

lostmandan · Posted: Fri Nov 14, 2008 3:41 pm Post subject:

Also if at all possible, if you do this yourself, practice on something you don't care about. I have a reasonable success rate, but it didn't start out that way.

I find that patience and fairly steady hands will reward with this sort of detailed rework. If things aren't going properly, walk away for a few minutes and take a break. Smile

jkruger · Joined: 24 Oct 2007 Posts: 2435 Location: Carlsbad, CA

I've used a safety pin or paperclip before.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Are you trying to save the chip your removing or is it no good?

JustGreg · Joined: 07 Mar 2006 Posts: 3098 Location: Kenosha, WI

I replaced bad memory on my Original Xbox 360 using a 60W soldering iron and desoldering wick. I have plastic tools from work and one is wedge shaped on the end. I lifted about 10 leads and then got the tool under it to keep some lift going on.
Then I thought to do this: If you don't care about the old IC, (which I didn't) cut all 200 leads off and deal with the stubs that are left. Then you can heat a select number (use a blunt wide tip on the iron) and solder wick, and just smear them into the center of where the chip used to be. (As long as there are no components underneath where it was of course). If there's nothing there to stick to you can just pick them up with a small piece of duct tape or the stickiest tape you can find. You don't want to blow them off. They'll end up everywhere (you don't want them).

Resoldering the replacement is what was mentioned earlier. Flow a crap load of solder across the leads...they'll look like you really frigged it up and connected them all, then use solder wick to remove the excess. When it cools, use a small pick to gently poke at the leads to see if they move. If you find any that move, obviously redo the blob solder method in that area.
<shrug> That method worked for me and I'm far from a Curt, MP, Athanasios, Nashou, etc.

RVonse · Joined: 09 Mar 2006 Posts: 3152

The closest I could come to piano wire was unwraveling an old coil off an old junk tv chassis I happen to have. It was really thin and somehow made it under the pins.

It worked perfect! The chip is now off and the board still looks in decent shape. Now the challenge is to get the new chip on it but I think I'll probably manage.

Thanks very much Dan, that wire idea worked out perfect!

CIR Engineering

CIR Engineering · Posted: Fri Nov 14, 2008 5:51 pm Post subject:

Fancy hot air rework:
http://www.youtube.com/watch?v=w1pxKN4UAXg

More basic:
http://www.youtube.com/watch?v=AxYhF6Ab2CU

http://www.youtube.com/watch?v=E_dfVo7gExI

http://www.youtube.com/watch?v=uSJ5hzx3lkc

craigr

CIR Engineering · Posted: Fri Nov 14, 2008 5:57 pm Post subject:

Interesting idea...

http://www.youtube.com/watch?v=zclj4waulAQ

http://www.youtube.com/watch?v=W4Coozv2DdE

craigr

**Curt Palme** · Posted: Fri Nov 14, 2008 6:02 pm Post subject:

CIR Engineering · Posted: Fri Nov 14, 2008 6:10 pm Post subject:

CIR Engineering · Posted: Fri Nov 14, 2008 6:13 pm Post subject:

It's fun Curt Thumbs Up

I have this station and it has been great for several years now (eBay item number 120333948587).

I also purchased an extra heating element and many many many soldering tips when I bought mine. It is Chinese so I was concerned about the ability to get replacement parts in the future. I also got a vacuum IC popper that plugs into the unit and is fed from the pump to lift IC's with little force when they get hot enough.

craigr

CIR Engineering · Posted: Fri Nov 14, 2008 6:24 pm Post subject:

This is pretty much the exact technique I use when I reattach an IC.

http://www.youtube.com/watch?v=V_cDV92IuWY

craigr

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Yeah!!! A rework Hot Air station is where its at, I got mine new for 159 dollars IIRC, bought the tweezer Iron too, Now Id like to get that IC suction thing in that one video, that is neat !

Athanasios