Yves:
We have just started into the 1.0mm BGA's ourselves. Our PCB Assembly
yields have been identical (actually slightly higher) than the 1.27. Of
course we are in the <300 ball regime for the 1.00, whereas we were in
the >400 ball range for the 1.27. Package size appears to have a great
deal to do with our yields. If we use a 1.00 27X27 at 196 balls, we get
better yeilds than a 35X35 1.27 at 196 balls. Likewise a 452 ball 35X35
1.00 yielded better than a 40X40 452 1.27mm package. Most of the
theories here have something to do with laminar coplanarity. The BT
substrate moves considerably (2~3X) in the Z axis during reflow (when
compared to all of the other materials).  Constrictions to this movement
and levers exist where the overmold package body meets the BT; likewise,
the center configuration will also be a localized constrictor.

Finally, we have also seen a vriation in yields when considering the
number of layers in the BT substrate as well. It may be where our
process is optimized (we originally did it for 4 layers). With 2 layer
or 6 layer subs we tend to get lower yields. So what we have don is
required all substrates to be at the same layer count on a given
assembly (i.e., no mixing of # of layers within a given assembly).

Hope this helps...

> Bill Davis, Ph.D.
> Diamond Multimedia Systems
> Senior Scientist
> Tel. 408.325.7868
> Cell. 408.888.5650
> e-mail: [log in to unmask]
>
>
>
>
> -----Original Message-----
> From: Yves Trudell [SMTP:[log in to unmask]]
> Sent: Friday, November 13, 1998 9:20 AM
> To:   [log in to unmask]
> Subject:      [TN] 1mm PBGA Assembly
>
> Dear TechNetters, we're venturing into assembling 1mm BGAs onto our
> PCBs.
> We're starting with a 196-pin PBGA package.
> If you have experience with assembling this package technology onto
> PCBs,
> what kind of assembly (not electrical) yields (DPMO) do you consider
> to be
> good?  If you don't feel comfortable in sharing this information in a
> quantified manner, how does it compare to other PBGA packages such as
> 1.27mm
> pitch?
>
> Yves Trudell
> Nortel, Wireless Networks Calgary
> Quality System Engineering
>
> ################################################################
> TechNet E-Mail Forum provided as a free service by IPC using LISTSERV
> 1.8c
> ################################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in the body:
> To subscribe:   SUBSCRIBE TechNet <your full name>
> To unsubscribe:   SIGNOFF TechNet
> ################################################################
> Please visit IPC's web site (http://www.ipc.org) "On-Line Services"
> section for additional information.
> For technical support contact Hugo Scaramuzza at [log in to unmask] or
> 847-509-9700 ext.312
> ################################################################
>

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################