Liverpool BeO Forward Hybrid with ABCD2-P


Introduction

A Liverpool BeO Forward Hybrid has been populated with 6 x ABCD2-P (thinned) to one side only. The chips are mounted onto individual Aluminium foil substrates using conductive glue. Wire bond connections, of imporatance, are: The ABCD2 has Edge Detect enabled and is using Edge Data Compression , unless stated.
40MHz clock mark-space ratio set to 1:1.
Nominal values of  VCC = 3.5V and VDD =  4.0V (measured on hybrid).
VCC and VDD are floating, Bias Card BC96 is not used.
Single trigger data collection.
 

Chip Location and ID

Chip Location
1
2
3
4
5
6
Wafer ID
P3-14
P3-15
P3-00
P3-07
P2-07
P4-15
 
 
* ABCD2 with no detector

* ABCD2 with detector

*ABCD2 oscillation fix


ABCD2 performance with no detector

Digital tests indicate that all 6 (1 to 6) chips work: Analogue testing reveals:  Optimum settings are tabulated below:
 
Chip
F.E.Bias (uA)
Shaper Bias (uA)
Strobe Delay
1
239.2
18
25
2
239.2
18
25
3
239.2
19.2
25
4
n/a
n/a
n/a
5
239.2
19.2
21
6
239.2
19.2
23
 

Results

Using the settings, shown above, for F.E.Bias and Shaper Bias, the following results have been obtained for Input noise (fC), Threshold (mV) and Gain (mV/fC) vs Channel for nominal Qinj of 2.0fC and 3.0fC.

Observations



 

ABCD2 performance with Wedge detector

 Conditions

 Results

Using nominal settings for the F.E.Bias and Shaper Bias, 239.2uA.and 20.4uA respectively, plots are shown  for Input noise (fC), Threshold (mV) and Gain (mV/fC) vs Channel for nominal Qinj of 2.0fC and 3.0fC.

 Observations

ABCD2 Oscillation at Low Threshold

Of the 5 'working' chips only 2 work correctly in that no oscillation is observed at low threshold. The cause of this oscillation has never really been properly understood and thus the ability of being able to resolve has proved problematic.
Why 2 chips work, which both come from different wafers, compared to the remaining 3 chips (from the same wafer) which do oscillate initially suggested that the problem could be processing related. Recent correspondence has indicated that this is not the case, it appears that the main contributary factor is the electrical interface between the backplane of the chip and the foil substrate that the chip is glued to, this should be a low Ohmic connection. The integrity of this connection is determinded by the conductive epoxy and its application.

Results

Using the nominal settings for F.E.Bias and Shaper Bias, the following Scurves have been obtained for nominal Qinj of 2.0fC: Chips 1, 2 & 3 are not bonded to the detector. Chips 5 & 6 are bonded to the detector.
 

Preliminary Results for Forward Hybrid with detector

Again using the nominal settings for biasing, not yet optimised, the following results have been obtained for Input noise (fC), Threshold (mV) and Gain (mV/fC) vs Channel for nominal Qinj of 2.0fC.
 

Chips 1, 2 & 3 are not bonded to the detector. Chips 5 & 6 are bonded to the detector.

 



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Last modified: 03/02/99