"DaveC" wrote in message
al.net...
I need to desolder (with no damage to the components) some SMD ROM chips.
Is
there a good tutorial somewhere on the 'net about how to go about this?

The absolute best and cheapest way (in my opinion) to desolder SMD chips is
to use Chip-Quik. The "solder" they use has a VERY low melting point. Even
after 30 seconds or so, it's still in a molten state which allows you to
just pick up the chip with your hands.

More info he

http://www.chipquikinc.com/

-Tim


BTW, I found a great tutorial on technique and equipment (lo-cost, some of
it
make-yourself) on the 'net about soldering SMDs:

http://www.wku.edu/~barceed/SolderPage/index.htm

Thanks,
--
DaveC

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DaveC wrote:
I need to desolder (with no damage to the components) some SMD ROM
chips. Is there a good tutorial somewhere on the 'net about how to go
about this?

Some fairly in-depth stuff at http://www.circuittechctr.com/guides/8-0.shtml
--
Correct address is cpemma at mexbro dot co dot uk

On Sun, 4 Jan 2004 2:30:51 -0800, DaveC wrote:

I need to desolder (with no damage to the components) some SMD ROM chips. Is
there a good tutorial somewhere on the 'net about how to go about this?

BTW, I found a great tutorial on technique and equipment (lo-cost, some of it
make-yourself) on the 'net about soldering SMDs:

http://www.wku.edu/~barceed/SolderPage/index.htm

Thanks,

The following instructions will work for removing smd chips.

1.) Take an oven tray and cover with aluminum foil, place board on foil.
2.) Set oven to 300-350 degrees F. depends on solder type used.
3.) Place tray in oven for approx. 10-15 minutes
4.) Open oven door, grab a pair of tweezers and try lifting component. If
component does not lift close oven door and try again every 2-3 minutes until
successful.


That's it ...cheap too!



Remove "HeadFromButt", before replying by email.

In article et,
says...
I need to desolder (with no damage to the components) some SMD ROM chips. Is
there a good tutorial somewhere on the 'net about how to go about this?

BTW, I found a great tutorial on technique and equipment (lo-cost, some of it
make-yourself) on the 'net about soldering SMDs:

http://www.wku.edu/~barceed/SolderPage/index.htm

Thanks,


The author of that page - Eduardo Barcellos - should consider giving
proper credit to the original source of his idea
(www.usbmicro.com/odn/index.html). He presents the hot-air idea as if it
were his own.

It is an unfortunate trend that students steal ideas from the internet
and boldly present the information without due credit. A whole
generation of people without morals would be the downfall of society.

DaveC wrote:
I need to desolder (with no damage to the components) some SMD ROM chips. Is
there a good tutorial somewhere on the 'net about how to go about this?

Given your requirement is to avoid damage to the SMD components, I
assume you need to re-use them?

As Tim H. posted, Chipquik is ideal for SMD removal by hand as it allows
you to reflow solder at temperatures low enough to avoid heat damage to
the board or component - the tricky part is removing and cleaning the
component without bending any pins. Most of the SMD rework information
available assumes devices will be discarded after removal.

I use the stainless steel strips orthodontists wrap around teeth. Coat
the pins with copious amounts of paste flux and reflow the solder with
Chipquik. The lowest temperature setting on my soldering station is
~325F, hotter than required but not hot enough to cause damage. Be
generous with the Chipquik as this will make it easier to maintain
molten material on all pins simultaneously. When the device is ready to
lift, it will be floating in a puddle of flux and solder, now you can
slide the stainless strip between the board and device to pick it up.
Warming the board from the underside with a hair dryer while working
facilitates the process. Where possible, slide the stainless strip under
the device body first, then keep it parrallel to the row of pins as you
move it under them to avoid bending. QFP devices are more difficult as
there's no 'pinless' side from which to access the underside of the
body, but trimming the stainless strip to a tapered point and starting
at one corner works reasonably well - the key is to make sure the device
is floating and avoid any sideways pressure on the pins. The stainless
strip method has the advantage of leaving the site much cleaner than
simply lifting the device with tweezers, so I use it when removing dead
devices too.

The freshly removed device will be somewhat protected by a coating of
Chipquik bridging all the pins, but still must be handled carefully.
Next you need a clamp capable of holding the device body while leaving
the pins accessible - mine came from the orthodontist. Hold the clamp at
an angle to the edge of the workbench, reflow the Chipquik with the iron
and tap the clamp against the edge of the bench to flick the pins clean.
Results are best if you can flick all the material off a row of pins in
one shot, so allow time for complete reflow before tapping the clamp.
The Chipquik can be collected and re-used several times.

HTH

Sunny


BTW, I found a great tutorial on technique and equipment (lo-cost, some of it
make-yourself) on the 'net about soldering SMDs:

http://www.wku.edu/~barceed/SolderPage/index.htm

Thanks,

Given your requirement is to avoid damage to the SMD components, I
assume you need to re-use them?

As Tim H. posted, Chipquik is ideal for SMD removal by hand as it allows
you to reflow solder at temperatures low enough to avoid heat damage to
the board or component - the tricky part is removing and cleaning the
component without bending any pins. Most of the SMD rework information
available assumes devices will be discarded after removal.



I had to replace an FPGA on a development board once. I used a $20 heat gun
clamped in a partially-completed CNC machine I was building. It only takes a
few seconds for the solder to melt when the heat gun is on its lowest
setting. I also used the heat gun to solder on the new FPGA, then touched up
a few pins with a soldering iron. Ideally there would be a heat shield to
prevent heating up other components, but in this case it wasn't a problem.
The pins heat up so much faster than the rest of the chip; all you need to
do is keep the internal temperature of the device less than 450 degrees F.
Here's a photo of the removed chip:
http://www.macetech.com/desolder-close.jpg