Bonding Stereo Modules

1
Bonding Stereo Modules
1
2

• We found a few problems bonding on the region of
  the pitch adapter not supported directly from the
  back (1). With difficulties (i.e. time and
  effort) we managed to bond/re-bond on some of
  these channels with a loss of only 2 channels in
  total (out of 30 modules bonded). But in many
  more cases some doubt remains on the strength on
  the bonds.
• This problem appears to us more severe than for
  the Axial module probably due to the presence of
  the supporting ceramic (2) which forces us to
  support the bonding region further away.

2
Bonding Stereo Modules
3

• We mitigated the problem by adding an independent
  support (3) of the exposed ceramic, shaped left
  or right depending on the stereo type.
• It is also very important to insert a spacer
  (200um Al 120um Kapton tape) in the 2 gaps, in
  the attempt of better supporting the pitch
  adapter under the bonding pads. Still in some
  cases difficulties remain.

3
Bonding Stereo Modules
Bias ring
(b)
(c)
(d)
Guard ring

• We notice the presence of wiskers protruding from
  the wire-bond footprint (a) not present on the
  pitch adapter pads (b). This is in general not a
  problem.
• However, in some cases, for the bias wire-bonds,
  a big wisker may develop (c) shortening the
  bias ring with the guard ring. This problem is
  very hard to spot as the wisker develop along
  the direction of the wire-bond (d).

(a)
(a)