Hi Eric,

can you point us to the mechanical specs of the components you have problems
with? One picture (drawing) is worth a thousand words.
Or post some pictures of the failed assemblies somewhere, for us to see. You
can contact Steve Gregory for that.

Salutations,
Ioan

-----Original Message-----
From: Eric Castonguay
To: [log in to unmask]
Sent: 10/1/02 6:05 PM
Subject: [TN] Dual footprint on Stacked Memories

Technet,
we are using a very special component on our pcb designs that has dual
footprint (fine pitch and BGA arrays). This component is made of two
TSOP66
stacked in tower and have mixed terminals: gull wing leads and BGA
balls.
So, both TSOP are assembled together with an interposer PCB in order to
make a stack. Bottom TSOP is weld to motherboard and high-temperature
solder (lead-free paste) is used to weld TSOP leads to the interposer
pcb.
BGA solder balls are SN96/AG4 and also interfaced with motherboard.

First, is anybody out there ever used this type of lead-free package
before? Any success?

We had many issues so far at our CM with these stacked memories: open
contacts (microfractures, missing solder, poor wettability) and
misaligned
components. We think it is mainly because non-eutectic balls doesn't
reflow
with standard temperature profile (60 sec. at 183 deg. C with peak at
220
deg. C). Hence creating poor joints.

Regards,

Eric Castonguay
Hyperchip