Kapton Cable Quality Assurance Procedure

Toshiyuki Shiina

The University of Alabama in Huntsville

September 22, 1999

  1. Introduction

    This note documents the procedures, equipment, and specifications used in testing the kapton cables. The kapton cable is used in the MVD to connect the 256 readout traces of the silicon strip detector to the MCM and to supply bias voltage to the detector from the MCM. The kapton cable consists of five layers of materials as follows:






    We use 6 different kinds of kapton cables for 6 geometries of silicon strip detectors as shown below.





  2. Testing

    [Setup and Procedure]

    The cables received from ALLFLEX are clearly labeled, e.g. POM-01 (Production kapton cable Outer/Middle number 01). Then the visual inspection is conducted first. The cable is placed between glass plates under the microscope. It takes about 5-10 minutes to scan the trace side of the cable depending on the surface area. Cables that have discontinuities in the trace, inter-trace shorts, and/or very thin traces (trace width < 50% of nominal trace width) are marked as bad. At this stage a quick bias line continuity test is conducted with a handheld multimeter. The bias lines run on one side of the cable and go to the bias pads on the other side through via holes. Electrical continuity between the bias lines and the bias pads is tested by measuring the resistance between the former and the latter. Only kapton cables which pass the visual inspection and the bias line continuity test should proceed to the electrical QA test.

    Setup

    The second step is the electrical tests to ensure the visual inspection result. Two types of electrical tests are conducted. One is a measurement of inter-trace resistance to find inter-trace shorts. The inter-trace resistance should measure larger than 100 MOhms to ensure no cross signals between channels. The other is a measurement of resistance of two adjacent traces to find discontinuities in the traces. (Two traces are shorted together, and the resistance between two bonding pads are measured.) The 32 pin 200 micron pitch probes touch the bonding pads on the silicon end of the cable. LabView controlled switch box selects two adjacent traces, and the electrometer measures the resistance between them. In the inter-trace resistance measurement the circuit should be open and the resistance should measure infinity. In the trace resistance measurement the circuit should be closed through the shorting bar on the bonding pads on the MCM end of the cable and yield less than 10 Ohms. (The wiring has internal resistance of ~5 Ohms and cannot be eliminated.) The kapton cable resistance measurement scheme is shown below.





    Procedure



  3. Result

    If one finds low inter-trace resistance (suspect for shorts) or high trace resistance (suspect for discontinuity) that was not found in the visual inspection stage, the cable should be re-inspected under the microscope to locate the defects. A trained tester's eye can detect >95% of the defects visually, and the rest should be caught electrically, which is reconfirmed visually to ensure a 100% confidence in the cable's performance.

    All the inspection result is available in the form of hard-copies in the 3-ring binder note labeled "kapton testing data" and in the form of ASCII file table on the CD_ROM labeled "kapton testing data."

    Appendix - Links to the final kapton cable inventory list

     1. Inner/Bottom kapton cable data sheet
    2. Inner/Middle kapton cable data sheet
    3. Inner/Top kapton cable data sheet
    4. Outer/Bottom kapton cable data sheet
    5. Outer/Middle kapton cable data sheet
    6. Outer/Top kapton cable data sheet