How does this compare to a CCGA construction?

-----Original Message-----
From: Higgins Leo [mailto:[log in to unmask]]
Sent: Thursday, October 03, 2002 10:38 AM
To: [log in to unmask]
Subject: Re: [TN] TBGAs



I cannot fully understand your question, but it appears that the
construction you describe is not that of a typical TBGA.  A normal wire
bonded TBGA is constructed as follows:

The polyimide flex circuit film is adhesively bonded to a copper stiffener
with an opening in it to expose the die attach and wire bond area.  The
silicon die is die attached to the film using a fairly typical epoxy-based
material.  The die is wire bonded to the flex.  The die and wire are
encapsulated.  Solder balls are applied to the bottom side of the flex.
There are many variants to this construction to provide die-down
configurations and flip chip configurations.  In one variation, the copper
has a depression formed to act as a die attach cavity, and the flex unit
(with an opening to match the die attach cavity) is bonded to the cavity
side of the copper stiffener.  The die is then wire bonded to the flex and
encapsulated.  Here the stiffener also acts as a heat spreader.  In all
designs the copper stiffener keeps the solder balls coplanar, and allows the
TBGA thermal expansion to be reasonably close to the motherboard CTE.

Regards,
Leo Higgins

-----Original Message-----
From: Louis, Edwin @ CSE [ mailto:[log in to unmask]
<mailto:[log in to unmask]> ]
Sent: Wednesday, October 02, 2002 8:30 AM
Subject: TBGAs


Does anyone have experience using TBGAs? I understand that a thermal bond is

made between the lands on a ceramic chip
and a Copper laminate tape to which is added solder balls on the bottom of
the tape to make bond to PWBs. This is supposed to solve the CTE difference
problem. What is the nature of the chip bond to tape and how and why does it

survive CTE differences?
Does anyone out there have thermal cycling data on them and assembly
experience with them?

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