21 Dec
2007
21 Dec
'07
1:54 p.m.
If you feel this subject is too far off-topic, please respond
privately. OTOH, it just might help some who are trying to repair
some of the old gear that uses SMT.
At any rate, I've got some 68-pin TQFP packages that I need to mount
on a PCB. I've searched the web and become throughly confused over
recommendations.
I'd like to stay away from using a hot-air rework iron as I don't
think I have enough skill to use it without causing some damage to
the PCB or component. I'd like to use my temperature-controlled
Weller soldering station as the heat source. I'll also be using Sn-
Pb solder rather than lead-free.
Two approaches that I've seen for conventional soldering iron
mounting involve what I'll call "flood and suck" that involves
covering all of the leads on one side of the QFP on the PCB with
solder and then using a solder "sucker" (such as a Soldapullt) to
remove the excess.
The other approach uses solder wick (solder removal braid), laying
the braid over the QFP leads and PCB and heating and applying solder
*through* the braid to the leads.
I'm fairly confident that I could do either, but who's had real
success with either method?
Thanks,
Chuck
21 Dec
21 Dec
3:37 p.m.
On Fri, 21 Dec 2007, Chuck Guzis wrote:
Date: Fri, 21 Dec 2007 13:54:16 -0800
From: Chuck Guzis <cclist at sydex.com>
Reply-To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
To: cctalk at classiccmp.org
Subject: Slightly OT: TQFP mounting
If you feel this subject is too far off-topic, please respond
privately. OTOH, it just might help some who are trying to repair
some of the old gear that uses SMT.
At any rate, I've got some 68-pin TQFP packages that I need to mount
on a PCB. I've searched the web and become throughly confused over
recommendations.
I'd like to stay away from using a hot-air rework iron as I don't
think I have enough skill to use it without causing some damage to
the PCB or component. I'd like to use my temperature-controlled
Weller soldering station as the heat source. I'll also be using Sn-
Pb solder rather than lead-free.
Two approaches that I've seen for conventional soldering iron
mounting involve what I'll call "flood and suck" that involves
covering all of the leads on one side of the QFP on the PCB with
solder and then using a solder "sucker" (such as a Soldapullt) to
remove the excess.
The other approach uses solder wick (solder removal braid), laying
the braid over the QFP leads and PCB and heating and applying solder
*through* the braid to the leads.
I'm fairly confident that I could do either, but who's had real
success with either method?
Thanks,
Chuck
I've done the flood method many times, you dont actually need to use a solder
sucker or wick much if you use a _LARGE_ excess of flux, and tilt the card as
you solder each side so the solder you are 'flooding' with makes a little wave
following the soldering iron tip. If you have enough flux and the correct
angle (pins down and with a tilt to help the wave move), the surface tension
of the solder will pull the solder bridges apart at the end of the 'wave'.
Usually only the last two pins on a side will end up with a solder bridge.
requiring solder wick to remove.
That said, there is a danger in flooding: if you cant get it right in a few
passes, you may dissolve the copper pads in the excess solder, causing a
distinct lack of holiday cheer...
Best thing is to practice on cards/parts you dont care about.
Peter Wallace
11:52 p.m.
On Friday 21 December 2007 16:54, Chuck Guzis wrote:
If you feel this subject is too far off-topic, please
respond
privately. OTOH, it just might help some who are trying to repair
some of the old gear that uses SMT.
At any rate, I've got some 68-pin TQFP packages that I need to mount
on a PCB. I've searched the web and become throughly confused over
recommendations.
I'd like to stay away from using a hot-air rework iron as I don't
think I have enough skill to use it without causing some damage to
the PCB or component. I'd like to use my temperature-controlled
Weller soldering station as the heat source. I'll also be using Sn-
Pb solder rather than lead-free.
Two approaches that I've seen for conventional soldering iron
mounting involve what I'll call "flood and suck" that involves
covering all of the leads on one side of the QFP on the PCB with
solder and then using a solder "sucker" (such as a Soldapullt) to
remove the excess.
I've *never* heard this recommended. And with that setup you're talking about
pulling the solder out between the part lead and the trace without pulling
the trace off the board. I wouldn't care to try it.
The other approach uses solder wick (solder removal
braid), laying
the braid over the QFP leads and PCB and heating and applying solder
*through* the braid to the leads.
I'm fairly confident that I could do either, but who's had real
success with either method?
I've actually done very little with surface mount, mostly finding it not
worth the bother for salvage, but while attending a technical seminar some
time back (Yamaha P.A.C.E. if anybody's interested) they recommended the
second technique for dealing with some of their stuff that was surface-mount,
most notably a 286 Laptop they had out that had something like 16 MIDI ports
on the back of it. That's how I'd do it, anyhow.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
22 Dec
22 Dec
8:03 a.m.
On Sat, 22 Dec 2007, Roy J. Tellason wrote:
Peter Wallace
Mesa Electronics
(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.
Date: Sat, 22 Dec 2007 02:52:27 -0500
From: Roy J. Tellason <rtellason at verizon.net>
Reply-To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
Subject: Re: Slightly OT: TQFP mounting
On Friday 21 December 2007 16:54, Chuck Guzis wrote:
I've soldered at least at least 500 parts the flood way for protos over the
years, from SO packages to .5 mm 208 pitch QFPs. I think the flood method is
by far the best way, as when done properly, _NO_ pressure is put on the PCB
pads when hot (the main cause of lifted pads). This does not mean that you
create a solder bridge between every pin pair, the object is to have enough
flux and the correct board tilt so the surface tension prevents the bridges
If you feel this subject is too far off-topic,
please respond
privately. OTOH, it just might help some who are trying to repair
some of the old gear that uses SMT.
At any rate, I've got some 68-pin TQFP packages that I need to mount
on a PCB. I've searched the web and become throughly confused over
recommendations.
I'd like to stay away from using a hot-air rework iron as I don't
think I have enough skill to use it without causing some damage to
the PCB or component. I'd like to use my temperature-controlled
Weller soldering station as the heat source. I'll also be using Sn-
Pb solder rather than lead-free.
Two approaches that I've seen for conventional soldering iron
mounting involve what I'll call "flood and suck" that involves
covering all of the leads on one side of the QFP on the PCB with
solder and then using a solder "sucker" (such as a Soldapullt) to
remove the excess.
I've *never* heard this recommended. And with that setup you're talking about
pulling the solder out between the part lead and the trace without pulling
the trace off the board. I wouldn't care to try it. from forming in the first case. This results in a very
even solder
distribution, much better, faster, and easier than soldering pins one
at a
time and much less likely to damage the PCB...
The other approach uses solder wick (solder
removal braid), laying
the braid over the QFP leads and PCB and heating and applying solder
*through* the braid to the leads.
I'm fairly confident that I could do either, but who's had real
success with either method?
I've actually done very little with surface mount, mostly finding it not
worth the bother for salvage, but while attending a technical seminar some
time back (Yamaha P.A.C.E. if anybody's interested) they recommended the
second technique for dealing with some of their stuff that was surface-mount,
most notably a 286 Laptop they had out that had something like 16 MIDI ports
on the back of it. That's how I'd do it, anyhow.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
11:15 a.m.
On Saturday 22 December 2007 02:52, Roy J. Tellason wrote:
On Friday 21 December 2007 16:54, Chuck Guzis wrote:
The way that they taught us to do it in college was basically the same
way, except using solderwick to pull up the excess, instead of a solder
sucker.
The technique was basically to tack down the corners of the chip first,
so that the chip is/stays properly aligned with the board, and then
drag the soldering iron along each side (using a wedge tip), with the
solder along the trailing edge.. if you get just the right speed,
you'll get a good connection. Then, just take solderbraid and an iron
to pick up the excess.
It works, and unless you're careless (or using a 100W soldering gun or
something), it works pretty well, once you've tried it a time or two.
Pat
--
Purdue University ITAP/RCAC --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
Two approaches that I've seen for
conventional soldering iron
mounting involve what I'll call "flood and suck" that involves
covering all of the leads on one side of the QFP on the PCB with
solder and then using a solder "sucker" (such as a Soldapullt) to
remove the excess.
I've *never* heard this recommended. And with that setup you're
talking about pulling the solder out between the part lead and the
trace without pulling the trace off the board. I wouldn't care to
try it.
11:20 a.m.
On Saturday 22 December 2007 14:15, Patrick Finnegan wrote:
The technique was basically to tack down the corners
of the chip
first, so that the chip is/stays properly aligned with the board, and
then drag the soldering iron along each side (using a wedge tip),
with the solder along the trailing edge.. if you get just the right
speed, you'll get a good connection. Then, just take solderbraid and
an iron to pick up the excess.
I forgot to mention, coating everything in excessive amounts of flux is
essential..
Pat
--
Purdue University ITAP/RCAC --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
2:08 p.m.
From: pat at computer-refuge.org
On Saturday 22 December 2007 02:52, Roy J. Tellason wrote:
Hi
I've probably reworked 100's of boards. I've found the safes method
is to use a solder sucker and thin blade to move the lead around ( doesn't
absorb too much heat ).
Using the solderwick, I've found it is more likely to lift a lead. If you
make too much contact and can't heat it all, it is difficult to remove the
wick without damage.
I always add fresh solder and flux before sucking. If you don't get
a clean suck, add solder again and repeat. Don't try to clean the last
bit by reheating only, you need to re-add solder.
For through hole ICs, I will first clear the hole and then apply slight
sideways pressure with the iron. The instant the lead moves, remove
the heat. The lead will usually be free or have a tiny connection one
can break with pliers. If it didn't come lose, repeat by adding solder.
For surface devices I may just lift the leads one at a time after cleaning
solder or use a heat gun ( depending on package type ). Patience
and timing are what it takes.
Dwight
_________________________________________________________________
Don't get caught with egg on your face. Play Chicktionary!
http://club.live.com/chicktionary.aspx?icid=chick_wlhmtextlink1_dec
On Friday 21 December 2007 16:54, Chuck Guzis
wrote:
The way that they taught us to do it in college was basically the same
way, except using solderwick to pull up the excess, instead of a solder
sucker.
The technique was basically to tack down the corners of the chip first,
so that the chip is/stays properly aligned with the board, and then
drag the soldering iron along each side (using a wedge tip), with the
solder along the trailing edge.. if you get just the right speed,
you'll get a good connection. Then, just take solderbraid and an iron
to pick up the excess.
It works, and unless you're careless (or using a 100W soldering gun or
something), it works pretty well, once you've tried it a time or two.
Two approaches that I've seen for
conventional soldering iron
mounting involve what I'll call "flood and suck" that involves
covering all of the leads on one side of the QFP on the PCB with
solder and then using a solder "sucker" (such as a Soldapullt) to
remove the excess.
I've *never* heard this recommended. And with that setup you're
talking about pulling the solder out between the part lead and the
trace without pulling the trace off the board. I wouldn't care to
try it. 
27 Dec
27 Dec
1:35 p.m.
At 12:54 PM 12/21/2007, you wrote:
If you feel this subject is too far off-topic, please
respond
privately. OTOH, it just might help some who are trying to repair
some of the old gear that uses SMT.
At any rate, I've got some 68-pin TQFP packages that I need to mount
on a PCB. I've searched the web and become throughly confused over
recommendations.
I'd like to stay away from using a hot-air rework iron as I don't
think I have enough skill to use it without causing some damage to
the PCB or component. I'd like to use my temperature-controlled
Weller soldering station as the heat source. I'll also be using Sn-
Pb solder rather than lead-free.
Two approaches that I've seen for conventional soldering iron
mounting involve what I'll call "flood and suck" that involves
covering all of the leads on one side of the QFP on the PCB with
solder and then using a solder "sucker" (such as a Soldapullt) to
remove the excess.
The other approach uses solder wick (solder removal braid), laying
the braid over the QFP leads and PCB and heating and applying solder
*through* the braid to the leads.
I'm fairly confident that I could do either, but who's had real
success with either method?
I've never done it with either method.
http://www.youtube.com/watch?v=wQXhny3R7lk
28 Dec
28 Dec
1:19 a.m.
I've never done it with either method.
http://www.youtube.com/watch?v=wQXhny3R7lk
What shape of tip is he using?
6204
days inactive
6211
days old
8 comments
7 participants
participants (7)
-
bert＠brothom.nl -
cclist＠sydex.com -
dkelvey＠hotmail.com -
grant＠stockly.com -
pat＠computer-refuge.org -
pcw＠mesanet.com -
rtellason＠verizon.net