Steve,
It's exactly VME Backplanes that we use press-fits for. They're about the
same number of layers, but much thicker for rigidity (0.250" !) We have a
bunch of small discretes on the underside and some SOIC16's etc. Really
don't envy you the BGA RAM chips with that thickness of board and press-fit
conns. Oh! The Flexure! I hope your board's physical support is really good
so you don't pop the BGA's off during pressing (I presume you're fitting
components first, as I don't know what thermal profile temperatures will do
to the connector pin: hole barrel interfacing.Certainly the pins will
expand and the hole diameters will contract with temperature and the pin
corners will cut even more into the plating. Then when they cool again
....)
Good luck, Buddy!
Peter
[log in to unmask] 28/10/2002 09:01 AM
To: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group@ST Domain, [log in to unmask]
cc:
Subject: Re: [TN] Press fit connectors...
Thanks Peter!
I'm about to build a VME card that's density is beyond belief, that
utilizes press-fit connectors. When Jack suggested that they be soldered as
a standard practice, I almost had a coronary!!!
Just to let you know, we're talking about a 16-layer, .062" thick board,
with a of bunch .020"-pitch components on the bottom, along with BGA RAM on
the bottom...
No wave at all...so Jack, do we hand solder this stuff? Remember, we're
talking 16-layers...
-Steve Gregory-
Hi, Steve,
Press fit connectors are just that - press fit - and they are designed not
to be soldered. The quality, diameter and tolerance of the plated hole
into
which they are pressed is critical, though, for successful press fitting,
but you must know all this. If you then solder the pins you'll have the
devil's own job getting them out again, quite apart from not having enough
clearance in most cases
At least for class 3 boards, wherever I've been, we mechanically support
them as well - nuts and bolts, though I've also seen them just pressed
with
no mechanical support, and they've worked fine, especially high pin-count
conns with plenty of insertion/extraction force. Check out the Harwin .com
site for info.
If incompetence is being sought, I suggest that your customer review their
requirements, assumptions, source information, etc., before slinging mud
at
you.
Peter
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