In a message dated 3/9/99 7:05:30 AM Pacific Standard Time,
[log in to unmask] writes:
<< Fellow techies:
We are going to be using an Actel CQ132 Ceramic Quad Flatpack (25 mil
pitch). From a process standpoint I have ordered a die from Fancort to form
the part, and we will be dispensing solder paste through a Camalot Poisitve
Displacement pump (can't stencil due to component location), component will
be placed then run through my Heller 1088 reflow system. All this forming
and dispensing stuff is new to me but the pitch and the reflow is not.
There is one part of the process that I'm taking for granted and that is the
tinning of the part. The part is received with gold leads.(Doesn't come in
anything but gold, and besides, the part will not form well with solder on
the leads) I'm assuming that after the part is formed, I can dip the feet
of the formed part in RMA flux then tin in a 500 degree F solder pot like
any other part, one side at a time. I would then clean the part in
Flux-Off-CZ then place into my matrix tray to hold until placement time.
I'll probably use a vacuum pencil to hold the part.
Is the tinning of this part as routine as I think its going to be or do I
need to worry about another new process ? Recommendations are needed.
Bill Kasprzak
Moog Inc.
(Have we hit the 2000 mark yet ? [Just havin' fun Steve, I know how it
feels])
>>
Hi ya' Bill!
Watch the Las Vegas 400 this last weekend? Pretty decent race...I bet the
two Burton brothers were diggin' it going side-by-side, one-two like that at
180 mph for the last 10-20 laps of the race!
Yeah, I don't think I'll ever live that 2000 thing down (GRIN)...fact,
my headstone will probably say; "Here lies the Millenium Man...'cept he was
200 years late" hehehe...
Anyhoo, them gold plated ceramic QFP's...myself, I don't think I'd mess
with trying to pre-tin them myself...especially since that's what a company
called Six Sigma does for a living (408) 526-1350, or you can get to their WEB
page by going to www.solderquik.com.
The reason I say that is because I built boards for a company called MIPS
a while ago (they got gobbled-up by Silicon Graphics I think..) and they had
these little 31-mil and 25-mil, 32-pin and 28-pin gold plated QFP's that we
had to place...RISC processors I think they were. Had to put these tall heat
sinks on them after we built the boards, BOY was that fun! That's a whole
nuther story though...
They needed to be pre-tinned as well, but the problem was that you could
very easily bridge adjacent pins because the solder would flow up the leads
and short to each other up next to the body very easily, the part was like a
ceramic "sandwich" where the leadframe and the die was in between. There was a
very,very, VERY fine line where if you dipped the part too deep in the solder,
it would wick and short...then yo' inna heap o' trouble boy...ain't easy
clearing shorts from there where that happens. I don't know if your part is
put together like the one did was.
Six Sigma has robots and everything for doing that kinda stuff...I was
worried that the parts might have trouble passing a FUJI FIP vision check
before I built my first board, but when I got them back it was a concern that
I didn't even have to worry about, the parts placed fine!
-Steve Gregory-
P.S. Still workin' on getting my wave solder up...
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