If the board is of high volume, can you get the designer to change the soldered resistor net works to press-fit SIP-Sockets and plugged in SIPs? Would that be even better or would it add extra steps to your process?
Regards,
Lakshmi
----- Original Message -----
From: Steve Gregory
To: [log in to unmask]
Sent: Monday, April 14, 2003 8:32 PM
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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