I have a piece of equipment that has a ROM chip in it which I'd like to
upgrade to a newer firmware revision.

I don't want to destroy the old EPROM by cutting the pins, but I'm
finding it very hard to desolder the 28-pin chip from the board using an
iron and solder sucker.

Is there a better way to do this?

Chemwick. Not as good on two sided plated through holes but usually works well enough.

You mean a desoldering bulb ? Those aren't that good. For plated through, something like a Hakko 808 works well. On lead free, you have to turn the heat all the way up. Also, when you see it melt, do not push the vacuum button tight away or else you will have an air pocket in there and solder at the top where you cant get a good thermal connection to it.

In any case, if it is lead free the first thing to do is to add some 83/37 to the connection.

Not tight away, right away.

And of course that is 63/37, not 83/37.

Half blind, can't type.

On Tuesday, April 26, 2016 at 7:31:15 PM UTC-4, wrote:
Not tight away, right away.

And of course that is 63/37, not 83/37.

Half blind, can't type.

Whle it is usually used to remove SMD components, Chip-Quik might be helpful here. Remove as much solder using solder-wik as you can, then apply the Chip-Quik. This with a little heat should allow for easy removal.

Dan

bitrex wrote:

I have a piece of equipment that has a ROM chip in it which I'd like to
upgrade to a newer firmware revision.

I don't want to destroy the old EPROM by cutting the pins, but I'm
finding it very hard to desolder the 28-pin chip from the board using an
iron and solder sucker.

Is there a better way to do this?
I have a Pace machine with a vacuum pump in it, and a hollow soldering tip.
It does an amazing job of desoldering parts even from multi-layer boards
with heavy copper planes. Generally, after using it, the parts just fall
free of the board. The trick is you heat the joint for about 6 seconds,
then "swirl" the tip around the hole once, and then keep swirling while you
hit the vacuum pedal. The vacuum pump can pump for a lot longer than the
plunger-type solder sucker. Usually I take 1-2 full seconds of vacuum while
swirling the tip, this gets ALL the solder out of the plated through hole.

When you do this, the swirling of the desoldering tip wiggles the end of the
component lead, making sure all the solder in the hole is extracted.

This works about 10 X better than the desoldering suckers, or even the
hollow-tip irons that have the vacuum plunger built into the iron.

Jon

On 2016-04-26 22:42:12 +0000, bitrex said:

I have a piece of equipment that has a ROM chip in it which I'd like to
upgrade to a newer firmware revision.

I don't want to destroy the old EPROM by cutting the pins, but I'm
finding it very hard to desolder the 28-pin chip from the board using
an iron and solder sucker.

Is there a better way to do this?

desoldering stations are great, but expensive...
I have one now but I had a soldier sucker before, and managed to
desoldier such circuits with quite success.
you must first re-soldier the circuit, with fresh leaded soldier
then use the soldier sucker, one pin at a time and it will come off
(except if it's a multi layer board there you really need a desoldering
station)

practice on another board you can destroy if needed.
good luck
--

Jean-Yves.

On 26/04/2016 23:42, bitrex wrote:
I have a piece of equipment that has a ROM chip in it which I'd like to
upgrade to a newer firmware revision.

I don't want to destroy the old EPROM by cutting the pins, but I'm
finding it very hard to desolder the 28-pin chip from the board using an
iron and solder sucker.

Is there a better way to do this?

You have to practise the following on a scrap board , before going for
it proper.
Retouch solder on each pin, mask off surrounding areas with a "frustrum"
made of PTFE slabs, tied together and tied to the pcb.
Blast the chip with freezer spray and then blast solder side with hot
air gun on full blast, ie as short as possible, while pulling the chip
from the other side with bent large circlip pliers, holding the board in
a vice while doing all this.

Jon Elson wrote:

Usually I take 1-2 full seconds of vacuum while
swirling the tip, this gets ALL the solder out of the plated through hole.

Any air flow (vacuum) after the initial sucking is a waste. The molten solder
is sucked away and the continuing air cools the area and... no more molten
solder.

The idea is to heat, heat, heat (as much as you determine is safe) and hit
the vacuum once. Repeat the whole process if required. If it is required,
usually longer heating period or higher heat is necessary.

jeanyves wrote:

you must first re-soldier the circuit, with fresh leaded soldier
then use the soldier sucker, one pin at a time and it will come off
(except if it's a multi layer board there you really need a desoldering
station)

Yes Ive found sometimes soldering a joint with fresh solder before
de-soldering it makes the process easier.
Kind of a mystery why (except if the original is lead-free solder--we all
know about that...)

In article -
september.org, says...

jeanyves wrote:

you must first re-soldier the circuit, with fresh leaded soldier
then use the soldier sucker, one pin at a time and it will come off
(except if it's a multi layer board there you really need a desoldering
station)

Yes I?ve found sometimes soldering a joint with fresh solder before
de-soldering it makes the process easier.
Kind of a mystery why (except if the original is lead-free solder--we all
know about that...)

I just started playing with the surface mounted devices about 3 weeks
ago after working with the older types for about 50 years. Just glad
the old computer boards I have been practicing on must have had the
lead solder on them. They seemed easy to work with.

Then I got an old mother board that must have the lead free stuff on it.
Using the hot air gun was not difficult to get the old part off. When
I tried to clean up the pads the device was on with some solder wick
with the old setting of the soldering iron about all I got done was to
stick the braid to the pads. Cranked up the heat on the iron and still
not much luck. Finally heated the area with the hot air gun then used
the braid and iron and that worked much beter.

Any other good hints on workig with the lead free solder other than
preheating the board ? Even putting some tin/lead solder on the pads
don't seem to help.

DaveC wrote:

Jon Elson wrote:

Usually I take 1-2 full seconds of vacuum while
swirling the tip, this gets ALL the solder out of the plated through
hole.

Any air flow (vacuum) after the initial sucking is a waste. The molten
solder is sucked away and the continuing air cools the area and... no more
molten solder.

The idea is to heat, heat, heat (as much as you determine is safe) and hit
the vacuum once. Repeat the whole process if required. If it is required,
usually longer heating period or higher heat is necessary.
The vacuum has to last long enough to remove ALL the solder in one go. If
it doesn't, the tiny remaining bits of solder don't conduct heat to the far
end of the pin. With the hollow copper desoldering tip on the joint, it
does NOT cool off, in the second or two it takes to pull all the solder out.

I wish you could see this Pace unit work, it is totally amazing! I fairly
routinely desolder some 68-pin connectors, and they just fall off the board
when you are done.

Jon

On 27/04/2016 19:34, Ralph Mowery wrote:
In article -
september.org, says...

jeanyves wrote:

you must first re-soldier the circuit, with fresh leaded soldier
then use the soldier sucker, one pin at a time and it will come off
(except if it's a multi layer board there you really need a desoldering
station)

Yes I?ve found sometimes soldering a joint with fresh solder before
de-soldering it makes the process easier.
Kind of a mystery why (except if the original is lead-free solder--we all
know about that...)

I just started playing with the surface mounted devices about 3 weeks
ago after working with the older types for about 50 years. Just glad
the old computer boards I have been practicing on must have had the
lead solder on them. They seemed easy to work with.

Then I got an old mother board that must have the lead free stuff on it.
Using the hot air gun was not difficult to get the old part off. When
I tried to clean up the pads the device was on with some solder wick
with the old setting of the soldering iron about all I got done was to
stick the braid to the pads. Cranked up the heat on the iron and still
not much luck. Finally heated the area with the hot air gun then used
the braid and iron and that worked much beter.

Any other good hints on workig with the lead free solder other than
preheating the board ? Even putting some tin/lead solder on the pads
don't seem to help.




You have to overload each PbF joint with PbSn solder, the result is not
supposed to be pretty or pass QC, doubling the blob size at least,
to have good effect at reducing the required tempearature to desolder them

You have to overload each PbF joint with PbSn solder, the result is not
supposed to be pretty or pass QC, doubling the blob size at least,
to have good effect at reducing the required tempearature to desolder them

Yeah but on plated through holes that might result in a bog blob on the top of the board, which will be harder to heat up and suck out. You really need to heat the **** out of it to mix ALL the solder. And that is what creates this risk.

On Tue, 26 Apr 2016 22:39:36 -0500, Jon Elson
wrote:

bitrex wrote:
Is there a better way to do this?

I have a Pace machine with a vacuum pump in it, and a hollow soldering tip.
It does an amazing job of desoldering parts even from multi-layer boards
with heavy copper planes.

Agreed. I have and use an old Pace:
http://802.11junk.com/jeffl/crud/pace-desoldering-station.jpg
Note the gas brazing tip cleaning tool. You'll need it. There's a
glass tube inside the handle which also needs to be cleaned. The
vacuum inline filter also tends to get clogged every few years and
will need to be replaced. However, an automobile fuel pump filter
also works.

Pace desoldering stuff on eBay:
http://www.ebay.com/sch/i.html?_nkw=pace+desoldering

Generally, after using it, the parts just fall
free of the board. The trick is you heat the joint for about 6 seconds,
then "swirl" the tip around the hole once, and then keep swirling while you
hit the vacuum pedal. The vacuum pump can pump for a lot longer than the
plunger-type solder sucker. Usually I take 1-2 full seconds of vacuum while
swirling the tip, this gets ALL the solder out of the plated through hole.

When you do this, the swirling of the desoldering tip wiggles the end of the
component lead, making sure all the solder in the hole is extracted.

Yeah, that works but I do it a bit differently. I "swirl" the tip
around to get the last bits of solder, but I don't try to clean the
hole at this point. Once the part is removed, I either make another
pass with the vacuum pump, or I clean up the mess with an ordinary
soldering iron and a mechanical solder sucker. The problem is that if
I use too much vacuum, the solder gets cold, turns to dross, and is
then difficult to reflow or remove.

This works about 10 X better than the desoldering suckers, or even the
hollow-tip irons that have the vacuum plunger built into the iron.

I have several soldering irons with hollow tips and either a bulb or
mechanical vacuum solder sucker attached. They were a waste of time
and money. The Pace vacuum desoldering station works the best.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In article ,
bitrex wrote:

I have a piece of equipment that has a ROM chip in it which I'd like to
upgrade to a newer firmware revision.

I don't want to destroy the old EPROM by cutting the pins, but I'm
finding it very hard to desolder the 28-pin chip from the board using an
iron and solder sucker.

Is there a better way to do this?

Go ahead and cut the pins, but as close to the board as possible. Then
solder the "amputee" to a 28-pin header. You stand a far smaller chance
of damaging it that way, than if you try to get all the legs out at
once. Also much less chance of ripping the plating out of any of the
holes.

Isaac

"bitrex" wrote in message
...
I have a piece of equipment that has a ROM chip in it which I'd like to
upgrade to a newer firmware revision.

I don't want to destroy the old EPROM by cutting the pins, but I'm finding
it very hard to desolder the 28-pin chip from the board using an iron and
solder sucker.

Is there a better way to do this?

The type of soldering iron with a rubber bulb solder sucker attachment can
work well, but if you take care to avoid damage from the recoil, a piston
type solder sucker can also work.

add flux and make sure all the solder is liquid before activating the
sucker.

If at first you don't succeed - remake the joint with fresh cored 60/40
solder and try again.

As long as you can shift about 90% of the solder out of the hole; you can
wiggle each pin free with small pointy nose pliers. Sometimes the chip will
almost fall out, but an overlooked sliver of solder can rip a via out as you
pry the chip.

Before levering the chip; grip the chip body and flex it in each direction,
this will contribute to freeing stuck pins and also show up the ones that
need another visit from the solder sucker.

wrote in
:

On Tuesday, April 26, 2016 at 7:31:15 PM UTC-4,
wrote:
Not tight away, right away.

And of course that is 63/37, not 83/37.

Half blind, can't type.

Whle it is usually used to remove SMD components, Chip-Quik might be
helpful here. Remove as much solder using solder-wik as you can, then
apply the Chip-Quik. This with a little heat should allow for easy
removal.

Dan

+1. Chip-Quik will get the melting point of the remaining solder down to
around 100 deg C so you can keep all 28 joints molten with a hot air gun
on a fairly low temperature setting without cooking the board.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL