Tips for removing stubborn, big PLCC chips with hot air?

[Steve Rieck]

I'm trying to remove the GLU from a IICX board without damaging it. Currently "practicing" on the NUCHIP which I don't need. Removed as much solder as I could with wick and put plenty of flux on the pins.

Then attempted to remove the NUCHIP with hot air using all the technique I'm familiar with. Unbelievably stubborn and my temperature is too high to begin with. I don't have the heart to punish what seems like a good un-corroded GLU chip this way.

Any veterans have advice on the safest way to get these big chips off the board? Thanks in advance.

 

[vtgearhead]

I try to use a pre-heater whenever I'm working on a multilayer board. If you bring the entire vicinity up to around 200C it's much easier to convince things to let go when you hit them with hot air.

 

[bakkus]

Start by adding fresh solder - low-melt solder if you have it.
This way you're not battling 30 years of crust at the same time.

I know you said you wicked off the old stuff, but adding solder actually helps distribute the heat among the pins.

 

[YMK]

An IR preheater makes it much easier and safer.

Use flux, hot air and shield surroundings with metal tape.

 

[jmacz]

ChipQuik low temp solder also works.

 

[Steve Rieck]

Got the GLU off. Not without a fight and too much heat. One thing I realized, in the case of a badly battery bombed board where you know you're not gonna want the board, after the solder has at least weakened significantly, you can pry the chip up from the corners with tweezers which will take some of the pads off the board. But it actually may be less stressful (less extended heat) on the chip you're trying to extract. The pads will lift well before there's enough pressure to damage any of the pins on the chip. That is my theory at least. Then you can simply clean the torn pads off the chip. Certainly a try that at your own risk kind of thing but it seemed to work for me. This is only necessary in the case of the very large chips. The smaller ones come off easily with hot air. If you think that's crazy and/or stupid, you might be right but it worked for me yesterday at least. Only do this with an unredeemable board of course.

As a test, I just ripped the NUCHIP off a IICX board with absolutely no heat. Just put curved tweezers underneath the corner and pryed it up. Came off with no pin damage and ripped a bunch of pads. Zero heat. Again not recommending this as a procedure. Just doing it for science.

 

[trag]

Adding generous amounts of flux and working in fresh solder can help dilute the hard crusty old bit.

 

[demik]

Without a pre-heater, I usually heatgun from the back and pull the IC off with tweezers. Only works of you don't want toi keep the board of course.
The variant without tweezers is to have the board upside down and something soft that will catch the IC (you may need to tap the board a little bit)

A bit crude but it works. Nice that you got your GLU off this way

 

[Steve Rieck]

Without a pre-heater, I usually heatgun from the back and pull the IC off with tweezers. Only works of you don't want toi keep the board of course.
The variant without tweezers is to have the board upside down and something soft that will catch the IC (you may need to tap the board a little

Seems to me that all old large PLCC chips like GLU's are not equal on these old boards after 35 years. Some are so stuck to the board that it's just unbelievable trying to get them off and others come right off.