Freiburg Kapton Forward Hybrid (Kapton3)

    * Hyrid/Module Performance with no Detector
    * Hybrid/Module Performance with Detectors


Introduction

A Freiburg Forward  Hybrid (Kapton 3) populated with 12 x ABCD2T  is currently under evaluation here at Liverpool, the intention is to construct an ATLAS Forward Module (the readout chips will be wire bonded to 12cm Silicon Detectors) which will then be used in a 'Forward Module System Test' based at CERN. Performance of the module will be evaluated with and without the Silicon Detectors bonded to readout.
The DAQ (DRAFT+SEQSI) is linked to a modified Melbourne Support Card (Opto Hybrid) V2.0 for pseudo optical operation, this includes a BPM encoding circuit (for the encoding of Clock and Command) with Kapton interconnects between the support card and hybrid. The Doric and VDC are driven electrically not optically.

Hybrid/Module Performance with no detector

Operating Conditions

Vdd = 4.00V (measured on hybrid)
Vcc = 3.50V (measured on hybrid)

Bias Current = 267 uA
Shaper Current = 30uA

Strobe Delay = 28

Edge detect is enabled
Compression mode is Edge (01X)

The module is organised so that the top and bottom of the hybrid are readout as individual planes into the DRAFT (due to constraints with the DRAFT, the DAQ is restricted to only a single plane readout at anyone time), their nomenclature is as follows:
 
Top M0 S1 S2 S3 S4 E5
Bottom M8 S9 S10 S11 S12 E13


Chip Trimming

Without trimming, Trimdac's are set to 0, the Vmean values for Qinj = 2.0fC, are as follows: Vmean after trimming for Qinj = 1.0fC and 2.0fC, the algorithm adopted aims to trim the maximum number of channels with minimum spread:
Untrimmed and Trimmed Response (Qinj = 2.0fC)
Channel Vmean (mV) Vrms (mV) Channel Vmean (mV) Vrms (mV) Untrimmed Channels
0 - 384 179.52 56.08 0 - 384 190.44 6.01 4
385 -767 193.39 51.93 385 - 767 190.97 6.38 8
768 - 1152 167.54 57.14 768 - 1152 190.37 8.45 28
1153 - 1536 167.86 49.91 1153 - 1536 189.37 13.59 25

As can be seen the action of trimming reduces considerably the spread of the Vmean, from 57.14mV to 13.59mV (worst case RMS for both). Unfortunately with the present trimming algorithm there is a trade-off between obtaining the maximum number of trimmed channels against being able to keep the value of Vmean uniform and consistent for the nominal value of injected charge.

Hybrid/Chip Characteristics after Trimming

Threshold Scans

Note that the horizontal axis (Threshold) is shown in DAC steps (2.5mV/step).
There is no evidence of oscillation at low threshold.

Gain and Input Noise channel by channel


Hybrid/Module Performance with W21+W22 Detectors  (Prelimanary) 

Hybrid is bonded to W21+W22 pair detectors, strip length (approx) 65mm and 54mm respectively, which gives a combined strip length of 119mm. The initial bonding of the readout to detectors takes the following format:

Important: AGND and DGND must be linked together, there are bond pads adjacent to each chip to allow this, for optimum performance.

Operating Conditions (as above)

Vdet = +100V
Idet = 4uA

Module is housed within a Faraday cage, the Faraday cage is linked to AGND on the support card.
 

Module Characteristics after Trimming

Observations

The module does not oscillate!

The results clearly show that there is a large number of bad channels, especially on the bottom plane. The primary cause of this problem is the chip to fan-in bonding where neighbouring channels have been found to be short-circuited to each other on the fan-ins. This is due to the close packing of the bond pads on the fan-in and hence when a wire bond is made there is a possibility of it short-circuiting to the neighbouring channel (as is the case for a large number of channels). As of present this problem cannot be rectified.
 
 
 
 



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Last modified: 28/07/00