[sci.electronics] tip for some...

fmgst@unix.cis.pitt.edu (Filip Gieszczykiewicz) (06/02/90)

	Greetings. I think that this subject has had all its
	life shaken out of it but here goes:


	A few days ago I got a 250W INFA-RED lamp (for $3.95)

	I put a mainframe board 1 inch from the bulb and turned
	the power ON. (remember 8 layer boards....)

	In 2 minutes I was able to use a chip puller to "yank"
	the chips from the component side. Neat!!!!

	That's not the punchline....


	2 things for best effect:

	1) Get a candle and deposit some carbon on the solder
	that you want to melt... (hold the board solder side
	down over the candle...) That way you can reduce the
	exposure time and also heat up maximaly only the area
	you want.

	2) Make a series of IR-absorbent-glass slides that have 
	a pattern "H" without the "-" bar.. make them in sizes of all
	the DIPs that you have on those boards... That way,
	you do not damage the board...


	IT WORKS. WE USE IT TO FIX VCR, TV, AND RADIO (and computers)
	in a repair shop I know... sure beats cutting the leads and
	unsoldering each pin... or using the "shitty" usoldering
	vaccum pump... or used a BLOW-TORCH (I have seen.... )

	By the way, if you use the slides, make sure they are
	IR absorbent glass and that they are GLASS or METAL. You'd
	be suprised how much heat 250Watts is.... 


	Sum up: If used properly with proper slides, one can remove
	even the "deathly" PGA and the 48 pin DIPs WITHOUT damaging
	the board or plated holes (which are a pain... as you've
	read here...) 


	Take care. 

	P.S. I have a feeling that someone may put me on a 
	"black list" for revealing this one ;-)

-- 
_______________________________________________________________________________
"The Force will be with you, always." It _is_ with me and has been for 10 years
Filip Gieszczykiewicz "..of future fame...." "Ok! So I have a dream..."
FMGST@PITTVMS  or  fmgst@unix.cis.pitt.edu "My ideas. ALL MINE!!"

ISW@cup.portal.com (Isaac S Wingfield) (06/04/90)

Filip Gieszczykiewicz writes:

>        A few days ago I got a 250W INFA-RED lamp (for $3.95)
>
>        I put a mainframe board 1 inch from the bulb and turned
>        the power ON. (remember 8 layer boards....)
>
>        In 2 minutes I was able to use a chip puller to "yank"
>        the chips from the component side. Neat!!!!

Some years ago, a friend got hold of a number of memory boards with the chips
soldered in; he didn't want the boards, only the chips. He would hold the
board by the corner, with pliers, and wave it around, about an inch above the
flame of his kitchen stove. When the solder got shiny (melted), he'd rotate
his wrist to place the chip side down, and rap the board on the edge of the
stove - hey, presto! all the chips would fall on the floor. Oddly, though, his
wife wasn't too fond of the metallic look the solder splats gave to the vinyl
flooring...


Isaac
isw@cup.portal.com
 

brian@ucsd.Edu (Brian Kantor) (06/04/90)

To bulk-pull chips, an easy way to desolder them all is to clamp one
edge of the board into a vise, go at the back of the board with a
diffuse blowtorch flame, and when all is molten, simply bend the board
towards you then then release it.  It will spring away, throwing chips
and molten solder all around.

Be sure to wear appropriate safety gear when doing this.  We used to do
it in the foundry area of the metalshop, where hi-temp labcoats, full
faceshields, and asbestos gloves were readily available.

Kiddies!  Don't Try This At Home.  These Men Are Professionals.

		- Brian

		"Beware of programmers bearing welding torches."

markz@ssc.UUCP (Mark Zenier) (06/05/90)

In article <14100@ucsd.Edu>, brian@ucsd.Edu (Brian Kantor) writes:
> To bulk-pull chips, an easy way to desolder them all is to clamp one
> edge of the board into a vise, go at the back of the board with a
> diffuse blowtorch flame, and when all is molten, simply bend the board
> towards you then then release it.  It will spring away, throwing chips
> and molten solder all around.

Unless they have bent over pins, or use those power distribution/bypass
capacitor strips that share the same holes.  At that point, a pair
of Visegrips and a insulated glove was called for.


Markz@ssc.uucp