Perhaps the assembler is using only 2 fiducials on their printer ?
Then the deviation can be partly due to the board, with the remainder resulting
from the fact that a 2 fiducial cannot compensate for rotation in the
machine.
----- Original Message -----
Sent: Friday, March 29, 2002 9:15
PM
Subject: Re: [TN] solder paste
registration
Hey Folks,
The solder paste is being applied with a stencil.
Thanks for all the info.
Tony steinke
----- Original Message
-----
From: Brian Ellis <[log in to unmask]>
To:
TechNet E-Mail Forum. <[log in to unmask]>; tony steinke
<[log in to unmask]>
Sent:
Friday, March 29, 2002 9:01 AM
Subject: Re: [TN] solder paste
registration
> Tony
>
> You don't say what type of
screen is being used. If it's a
> nylon/polyester one, then I'd say
you're in deep trouble. If it's a
> stainless steel one, it can still
stretch as the squeegee distorts it.
> You really should use a
stencil.
>
> Brian
>
> > tony steinke
wrote:
> >
> > Ladies and Gentlemen,
> >
>
> We are having a major problem with an assembly house with
registering
> > the solder paste to surface mount features prior to
pick and place.
> > They
> > are claiming that the boards
are growing/shrinking some 15-20 mils.
> > We have done extensive
measuring on unpopulated boards in-house
> > and cannot see more than
3-5 mils misregistration. The panel size
> > is approximately 14.00 x
16.00 inches, 20-24 mil pitch, and 15 BGA's
> > throughout the panel.
Overall thickness .080. Is it possible that the
> > mesh
> >
screen that they are using can expand/contract over time? has anyone
>
> heard of this experienced this situation before. Any information
would
> > be
> > greatly appreciated.
> >
>
> Thanks
> > Tony Steinke
> >
AIT-Atlanta
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