Or you could buy an IR rework station that will remove just about anything
(SMT & PTH) without all these nozzles and masking.
Peter
"Kasprzak, Bill (sys) USX" <[log in to unmask]> 15/04/2003 07:27 PM
Sent by: TechNet <[log in to unmask]>
Please respond to "TechNet E-Mail Forum."; Please respond to "Kasprzak,
Bill (sys) USX"
To: [log in to unmask]
cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: Re: [TN] An apology, and a question...
Steve:
What I would normally propose for your SIP's is to mask off the surrounding
solder joints with some combination of kapton tape and water soluble mask.
Heat the board in an oven for about 15 - 30 mins at 200 - 250 deg F. Take
the assembly from the oven then place the board with the exposed joints
over
a small solder pot then pull the part out. It's times like this that I wish
I had one of those Air-Vac solder fountains that has different nozzles to
make a mini wave machine for whatever part you want to remove or install..
A secondary method would be to cut the leads at the body then remove the
lead left behind using an iron and a pair of tweezers. Obviously, parts are
lost with this method.
Good luck, I'd like to know how you made out.
Bill Kasprzak
Moog Inc. Manufacturing Engineering, Electronics
> -----Original Message-----
> From: Steve Gregory [SMTP:[log in to unmask]]
> Sent: Monday, April 14, 2003 8:32 PM
> To: [log in to unmask]
> Subject: [TN] An apology, and a question...
>
> It seems sometimes that what I post opens a big can of worms...open
mouth,
> insert foot. I've received some emails directly, that have put me in my
> place.
>
> I want to apologize to everyone, and I promise to leave the list
> moderation up to the moderator; Jack Crawford.
>
> My hope is, that my occasional indiscretions can be forgiven. I try to
> support this distinguished list with whatever I can do. I just want to
say
> I'm sorry to everybody.
>
> Now on to my question. I've just recently been confronted with a big,
> thick, lots of copper back-plane. It's the same one I posted about wave
> soldering just recently. BTW, I was able to get satisfactory topside
> fillets by baking the assembly at 100 C., whisking out of the oven to the
> wave machine, fluxing the top-side, and hitting it with both the
turbulent
> and laminar waves.
>
> The next big challenge is rework. Wished we could have built them without
> having to rework anything, but we have a few SIP resistor networks that
> were put in with the wrong polarity, and it seems almost impossible to
> rework these guys without lifting a pad on the bottomside. The pads have
> no traces connected to them on the surface layer, and the barrel looks
> fine...it's just the annular ring pad is gone. I have a AIR-VAC PCBRM-12
> and I've tried to "Pre-heat" things by just placing the area into the
> nozzle, for a few seconds, then remove it, multiple times, so as to drive
> heat into the laminate, before I attempt the actual removal.
>
> I'm thinking I probably need to pre-heat the assembly over a fairly large
> area around where I'm trying to attempt rework, because the thickness of
> the PCB, and the way it sucks heat away from the rework location. I'm
> learning there is no-way to rework the PTH on a AIR-VAC the same way we
do
> with .062" boards. I'm thinking of a laboratory hot plate to pre-heat
> (that's because I have one here).
>
> Any tips or help that anyone can share would be greatly appreciated...
>
> -Steve Gregory-
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