In a message dated 12/22/98 8:50:18 AM Pacific Standard Time,
[log in to unmask] writes:
<< Hi all :
We are doing boards with components on Top and Bottom sides (2 reflows), 1st.
process is bottom and we do not have any problem, but for the 2nd. process we
need a pallet for having a uniform support on the board, because the height of
the solder paste is not regular.
Do somebody have information about a company(ies) that makes this kind of
pallets for supporting ?
Miguel Angel Pulido>>
Hi Miguel,
In reading the replies to you, it looks like everybody has given you some
good sources for pallets. I'd however, like to throw this out there regarding
pallets. There's always going to be some boards that's going to require
fixturing of some sort when being built, be it surface mount, wave-soldering,
what have you. But before I go and get pallets, I'll try to do whatever I can
to keep from having to use them. Look at the layout and make recommendations
to change things to keep the board as flat as possible.
You didn't mention how you ran the first side through reflow...do you use a
edge rail conveyer? I've had boards warp because of the component density
running on the edge rails, your answer to your problem could be as simple as
running the first side reflow on the mesh belt instead of the edge rails. If
its warping on its own,that many times indicates that the copper or components
isn't balanced, or distributed evenly throughout the board.
Maybe you have some input to change things, or maybe the board is such that
things can't be changed. At any rate, the big thing I have against using
pallets is that they're cumbersome and slow things down, and unless you have
big bucks and can afford a whole mess of them, your poor operators wind-up
putting in quite a few miles running the bloody things from the end of the
line back up to the beginning. Plus, they inhibit the use of other automation
like bare board loaders and unloaders, and will prevent you from running the
boards in a "flip-line" (one that does both sides in one pass) if you are ever
in a postion to have such a nice line. Also, sometimes they can add to the
weight of a board so much that they can't travel down the conveyer (I've had
that happen a time or two in the past with FUJI machines when I was having
pallets made from aluminum before all the lighter composite materials started
showing up...)
But if you gotta' have pallets, ya' gotta'. Everybody has given you some good
sources (SP Precision is one I've used before and they're good, another one is
Stone Mountain Tool, they incorporate some unique board clamping systems in
their pallets)
-Steve Gregory-
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