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Desoldering Problems for a transistor

Desoldering Problems for a transistor

2004-02-24 by sirish minapalli

Hello everybody...

I hope somebody could solve my problem with regards to soldering and desolderin a transistor. i'm currently workin on building a s-parameter test board for measuring the s-parameters of transistor. the plan is to hav a single board and make all students put their transistors on the board, measure s-parameters and then take it off. at first i thought solderin wud b good...but wats happening is while desoldering atleast one of the pins is getting broken . and by the time i melt the solder on all the 4 pads having 4 pins in order to remove the transistor, they become cold and i'm not able to take the transistor off...So i was wondering there shud b another way to do it. if nebody could come up with a suggestion, it would b gr8. thanks
regards
chris



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Re: [Homebrew_PCBs] Desoldering Problems for a transistor

2004-02-24 by Rick C.

Why not use a socket? Available from many supply houses. Digikey,
Jameco, etc.
Rick

sirish minapalli wrote:

Show quoted textHide quoted text
> Hello everybody...
>
> I hope somebody could solve my problem with regards to soldering and
> desolderin a transistor. i'm currently workin on building a
> s-parameter test board for measuring the s-parameters of transistor.
> the plan is to hav a single board and make all students put their
> transistors on the board, measure s-parameters and then take it off.
> at first i thought solderin wud b good...but wats happening is while
> desoldering atleast one of the pins is getting broken . and by the
> time i melt the solder on all the 4 pads having 4 pins in order to
> remove the transistor, they become cold and i'm not able to take the
> transistor off...So i was wondering there shud b another way to do it.
> if nebody could come up with a suggestion, it would b gr8. thanks
> regards
> chris
>
>


[Non-text portions of this message have been removed]

Re: [Homebrew_PCBs] Desoldering Problems for a transistor

2004-02-24 by Stefan Trethan

On Tue, 24 Feb 2004 12:54:26 -0800 (PST), sirish minapalli
<sirish4jobs@...> wrote:

Show quoted textHide quoted text
> Hello everybody...
>
> I hope somebody could solve my problem with regards to soldering and
> desolderin a transistor. i'm currently workin on building a s-parameter
> test board for measuring the s-parameters of transistor. the plan is to
> hav a single board and make all students put their transistors on the
> board, measure s-parameters and then take it off. at first i thought
> solderin wud b good...but wats happening is while desoldering atleast
> one of the pins is getting broken . and by the time i melt the solder on
> all the 4 pads having 4 pins in order to remove the transistor, they
> become cold and i'm not able to take the transistor off...So i was
> wondering there shud b another way to do it. if nebody could come up
> with a suggestion, it would b gr8. thanks
> regards
> chris
>

well, you heat one leg, just pull as much as the other legs will flex,
then do this with every
leg in turn. after some rounds (depending on how many legs the part has)
it comes off.

for temporary mounting it is much faster if you don't put it through a
plated hole but on solder
pins or such.

you coud use a solder sucker (please the expensive heated version).
you could use a iron big enough to heat all pins (special shape).
you yould use hot air to heat all pins.

you could use a socket (which is the best idea if you want not to teach
them soldering)

ask if you have further questions

st

Re: [Homebrew_PCBs] Desoldering Problems for a transistor

2004-02-25 by Ron Amundson

> > Hello everybody...
> >
> > I hope somebody could solve my problem with regards to soldering and
> > desolderin a transistor. i'm currently workin on building a
> > s-parameter test board for measuring the s-parameters of transistor.
> > the plan is to hav a single board and make all students put their
> > transistors on the board, measure s-parameters and then take it off.
> > at first i thought solderin wud b good...but wats happening is while
> > desoldering atleast one of the pins is getting broken . and by the
> > time i melt the solder on all the 4 pads having 4 pins in order to
> > remove the transistor, they become cold and i'm not able to take the
> > transistor off...So i was wondering there shud b another way to do it.
> > if nebody could come up with a suggestion, it would b gr8. thanks
> > regards
> > chris
> >
> >
Its hard to find a reasonably priced socket to measure S parameters. Diamond
powder sockets work well, and are used in production, but would be overkill
and way to spendy for educational purposes. You might see if you can create
a stable pogo nest in some really high dieletric material. You should be
able to charaterise it, and then remove its influence. Even the HP fixtures
have to be calibrated prior to s-parameter measurement.

Ron

Re: [Homebrew_PCBs] Re: Desoldering Problems for a transistor

2004-02-25 by Ron Amundson

----- Original Message -----
From: "Ben H. Lanmon" <bhleavi@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, February 24, 2004 9:52 PM
Subject: [Homebrew_PCBs] Re: Desoldering Problems for a transistor


> Put a socket on the board so they just plug and unplug the
> Transistor.
>
> Ben
>
Where are you finding sockets that are adequate to measure s-parameters? I
do a fair amount of RF design, and unless the socket is over $5,000 the
sockets parasitics kill the measurement.

Thanks
Ron

Re: [Homebrew_PCBs] Re: Desoldering Problems for a transistor

2004-02-25 by Ron Amundson

>
> Well, then the best will be to test it in "real life conditions".
> --> soldering. make a few boards to allow for changing them after a while.
>
> ST

I agree, but incoming inspection does not warrant the labor costs to solder
the parts in place, and I'm always looking for good ideas and lower priced
alternatives. Certinaly for prototyping and test, extra pcbs are the only
way to go.

Ron

Re: [Homebrew_PCBs] Re: Desoldering Problems for a transistor

2004-02-25 by Stefan Trethan

> Where are you finding sockets that are adequate to measure s-parameters?
> I
> do a fair amount of RF design, and unless the socket is over $5,000 the
> sockets parasitics kill the measurement.
>
> Thanks
> Ron
>

Well, then the best will be to test it in "real life conditions".
--> soldering. make a few boards to allow for changing them after a while.

ST

Re: [Homebrew_PCBs] Re: Desoldering Problems for a transistor

2004-02-25 by Jeremy Taylor

I've had good luck using a desoldering - powered suction type iron.
It will completely suck off all the solder on each leg individually. I use
my iron set on about 7 on the scale , so I'm assuming it's running at 30+
Watts, I only center the leg tip on the nozzle, attempting to not directly
contact it, and the solder - especially fresh solder, comes off very
quickly.

JT

---
http://www.soundclick.com/jtsound

----- Original Message -----
Show quoted textHide quoted text
From: "Ron Amundson" <ron_amundson@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 25, 2004 3:16 AM
Subject: Re: [Homebrew_PCBs] Re: Desoldering Problems for a transistor


> >
> > Well, then the best will be to test it in "real life conditions".
> > --> soldering. make a few boards to allow for changing them after a
while.
> >
> > ST
>
> I agree, but incoming inspection does not warrant the labor costs to
solder
> the parts in place, and I'm always looking for good ideas and lower priced
> alternatives. Certinaly for prototyping and test, extra pcbs are the only
> way to go.
>
> Ron
>
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
> Yahoo! Groups Links
>
>
>
>
>

Re: [Homebrew_PCBs] Re: Desoldering Problems for a transistor

2004-02-25 by Russell Shaw

Ron Amundson wrote:
>>Well, then the best will be to test it in "real life conditions".
>>--> soldering. make a few boards to allow for changing them after a while.
>>
> I agree, but incoming inspection does not warrant the labor costs to solder
> the parts in place, and I'm always looking for good ideas and lower priced
> alternatives. Certinaly for prototyping and test, extra pcbs are the only
> way to go.

Solder some thin beryllium copper strips onto the microstrip so that
the springness holds down the flat leads of the device onto the track.
There's little extra fringing effects then. If you're testing thousands,
just make a simple pick and place gadget that picks the transistor out
with a vacuum tube, holds it down against the pcb for the test, then
places it back into the packaging.

Re: [Homebrew_PCBs] Re: Desoldering Problems for a transistor

2004-02-25 by Stefan Trethan

On Wed, 25 Feb 2004 05:19:05 -0500, Jeremy Taylor <jt@...> wrote:

Show quoted textHide quoted text
> I've had good luck using a desoldering - powered suction type iron.
> It will completely suck off all the solder on each leg individually. I
> use
> my iron set on about 7 on the scale , so I'm assuming it's running at 30+
> Watts, I only center the leg tip on the nozzle, attempting to not
> directly
> contact it, and the solder - especially fresh solder, comes off very
> quickly.
>
> JT
>

I have worked with such a unit in the past, it is great.
it was all (pump and all) contained in a gun like unit.
it is way better than the "piston type solder suckers".
They tend to suck off the pads too, and that sucks ;-) .

I already have made a nozzle from copper, to fit a 80watt iron.
But i have not had time to make the vacuum.
(i tried with a fridge compressor suction side and it works fine.
but you have to store the vacuum in a container, the fridge pump
can't generate it fast enough. (with a valve and a button to switch it
on on the soldering iron)

I must look for replacement nozzles, for professional desolder irons, my
copper
tip will not last long....

I have hooked it all up with the compressor and all some time ago and it
worked
pretty well....

ST

Re: [Homebrew_PCBs] Re: Desoldering Problems for a transistor

2004-02-25 by Ron Amundson

> Solder some thin beryllium copper strips onto the microstrip so that
> the springness holds down the flat leads of the device onto the track.
> There's little extra fringing effects then. If you're testing thousands,
> just make a simple pick and place gadget that picks the transistor out
> with a vacuum tube, holds it down against the pcb for the test, then
> places it back into the packaging.
>
Thats a great idea.I'm so used to using pogo's I had never thought of a DIY
spring right on the microstrip. This is very good.

Ron

Re: Desoldering Problems for a transistor

2004-02-25 by sirish4jobs

Thanks a lot everyone for ur suggestions...i really appreciate
it...i looked around for sockets, but i find them to b really
expensive and probably my prof wont allow me to use them for labs.
this is wat i did - > i silvered the copper pads first to prevent
further oxidation and to give a cleaner surface. then i placed the
transistor on the pads and put a tape on it to hold it to the PC
board. and checked in the network analyzer. i was seeing lotta
resonance points. so, i went ahead and tried to put some more
pressure on the transistor to hold it firmly to the pads. then i
could c no resonance points. So for now i'm using a clip arrangement
to exert pressure and that kinda works fine. its wooden clip and so
it isnt affecting my calculations. its not a permanent solution, but
hey it was an easy solution. any comments abt this ??
Sirish
--- In Homebrew_PCBs@yahoogroups.com, "Ron Amundson"
<ron_amundson@h...> wrote:
> > Solder some thin beryllium copper strips onto the microstrip so
that
> > the springness holds down the flat leads of the device onto the
track.
> > There's little extra fringing effects then. If you're testing
thousands,
> > just make a simple pick and place gadget that picks the
transistor out
> > with a vacuum tube, holds it down against the pcb for the test,
then
> > places it back into the packaging.
> >
> Thats a great idea.I'm so used to using pogo's I had never thought
of a DIY
Show quoted textHide quoted text
> spring right on the microstrip. This is very good.
>
> Ron

Re: [Homebrew_PCBs] Re: Desoldering Problems for a transistor

2004-02-25 by JanRwl@AOL.COM

Why hasn't some guru mentioned "solder wick" on this thread? With reasonable
digital (that's FINGERS for you orthographically-challenged) dexterity, one
can "clean off" a soldered-on part with NO damage, and leave things "pretty"!!!


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