How to remove thru-hole IC from multi-layer PCB? - Page 2 - diyAudio
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Old 19th February 2006, 12:48 AM   #11
poobah is offline poobah  United States
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If you have an electric stove... put the burner on high and wait until it is dull red... place the IC and board over the burner... in a few seconds... lift it out.

Before you do any of this... you had better have your story made up for your wife...



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Old 19th February 2006, 02:00 AM   #12
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Default Removing IC

Hi Alexandre,
same name as me, almost. I'm Alexander.

There have been a few suggestions above and I'm afraid most should be taken with a pinch of salt. No offence meant.

Patience is the name of the game, where a large number of pins need to be removed, unless you have the correct speed tools.

If the IC is important to you, then any method involving blowtorches, lighters and flame of any variety should be discounted fairly quickly, as the chip will almost certainly be fried. Especially if a large number of pins is involved.

Looking at the picture you have posted, your IC appears to be a 28 pin, or possibly 40 pin DIL.

It also appears, contrary to your post, that there is very little solder on the component side. Is this correct?

If so, then desoldering braid is probably the best way to go.

This braid works best when there is a reasonable amount of solder to work with, so examine the undeside of the board and silly 'though it might seem, like another poster above, I suggest that if the joints appear solder deficient, then re-solder the joints prior to de-soldering. Give the braid something to work with.

Use a good, hot, bolt and apply the braid to each joint but go from side to side of the chip, to spread the heat.

When you have done half of the pins, walk away and have a can of coke, or something, and let the chip cool down.

Go back and do the other half of the pins.

At this point, get a small screwdriver and press against the joints.

If they are free, you will easily see them move.

If not, press a bit harder and usually, the joint will break loose with an audible crack.

If it doesn't, re-solder the joint and de-solder with braid again. Don't waste your time trying to use braid on the previously de-soldered joint. Always re-solder.

Eventually, all the joints will free up and the chip will come out easily.

HTH,
Sandy.
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Old 19th February 2006, 06:21 AM   #13
Leolabs is offline Leolabs  Malaysia
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Try this method that lots of China repairman are using:
-solder all the pins together with enough solder wire.
-heat them all together by moving the soldering tip from end to end.
-use a test pen or tweetzer to pull the IC up,when all the solder melted.
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Old 19th February 2006, 10:40 AM   #14
Bobken is offline Bobken  United Kingdom
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Sometimes it can help if you spray the chip well with a freezer can before you begin, if you are attempting to desolder the pins as suggested.
In my experience this does not make much difference to the pins heating up if you are merely doing the removal this way, but might help to avoid frying the chip if the soldering iron is applied for longer than is ideal.

It wouldn't be a good idea if you are using a stove, or whatever, to heat the entire assembly, as this will just increase the time of heating overall.
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Old 19th February 2006, 10:53 AM   #15
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Hmm.

If this were my problem, I think I would just cut the pins as close to the PCB as possible rather than risk overheating something that might not be replaceable.

It is much simpler then to extend the pins for the new PCB, or if you go for a skeletal type socket, you might be able to solder directly to that.
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Old 19th February 2006, 02:11 PM   #16
poobah is offline poobah  United States
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If this were a single sided board, you could wick the pins or use a solder sucker; but its not. You will never get all the solder out of the holes.

Hot air is the "pro" way to do it, but you probably don't have a heat gun that will get hot enough.

A huge solder pot is a nice way to go... float the entire board on the solder, wait about 10 seconds and lift out chip. Bet you don't have solder pot big enough to float the board...

A desoldering tip that hits all leads at once is nice... got one?

Soldering all the pins together is nice... got 8 hands and 4 irons?

Seriously, throw a scrap board on the kitchen stove and practice. When you see how easy it is... report back.

Otherwise, use the PinkMouse method... cut the chip out and extend the leads later.
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Old 19th February 2006, 09:06 PM   #17
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You can get some 500°C heat guns for 20$.

You could use the toaster oven SMD soldering technique, but pull the chip while the solder is still melted instead of letting things cool down.

Also, in the wiki, there's an article on SMD rework. Maybe the DIY hot air pencil could work...

http://www.diyaudio.com/wiki/index.p...ntDeviceRework


You can easily cut the PCB with a metal saw also.
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Old 20th February 2006, 12:39 AM   #18
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First of all, thanks for all the suggestions!
I got the IC out in (supposedly) good shape. Havenīt tested it yet. I ended up using my soldering iron, and a special solder with a very low melting temperature. It stays melted for several seconds. The key here is to suck some of the old solder with a common desoldering pump, then put a lot of this low-temp solder over all pins of the IC. It stays melted so you have some time to force the IC out. It didnīt come out too easily though.
This product is sold locally with a name like "smd-saver".

(I just hope I havenīt overheated the IC.....)

Thanks & Best regards!!
Alexandre
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Old 20th February 2006, 12:56 AM   #19
sam9 is offline sam9  United States
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What ever you finally decide on, let us know how it worked. This a problem that everyone struggles with sooner or later and normally results in much aggro.
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Old 20th February 2006, 01:27 AM   #20
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Sam9: I described what I did on the post above! I havenīt tested the IC yet, but I think itīs OK!

-Alexandre
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