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Kapton bias circuits delaminations Alessandro Brez INFN - Pisa Brez@pifn.it

Gamma-ray Large Area Space Telescope. Kapton bias circuits delaminations Alessandro Brez INFN - Pisa Brez@pi.infn.it. The problem.

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Kapton bias circuits delaminations Alessandro Brez INFN - Pisa Brez@pifn.it

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  1. Gamma-ray Large Area Space Telescope Kapton bias circuits delaminations Alessandro Brez INFN - Pisa Brez@pi.infn.it

  2. The problem • Several trays show a delamination of the Kapton bias circuit in the peripheral area, up to the shield Cu plane. The shielding plane stays covered by the upper Kapton layer. • we had a first isolated case (tray MID093, back side, bias s/n 4606), i.e. 1 failure over 317 cases between SN/4000 and SN/4699 • batch with SNs/4700-4899 show much higher rate of defective bias circuits (9/47 glued to trays) • current batch (SNs 49xx) has not been used yet

  3. Test Method Kapton layers Cu shield plane double tape Al base The bias circuit is attached to an Al plane with a double adhesive tape A corner of the bias circuit is cut out with a scalpel The adhesion of the 2 Katpon layers is qualitatively tested with the scalpel edge , trying to remove the upper layer, simulating the trimming operation

  4. Test results from Bias circuit #4504 Good Bias circuit: Working hard with the scalpel it was possible to delaminate only very small flaps of the upper Kapton layer. The adhesion of the 2 layers is higher than the adhesion to the tape. Cu Kapton+Kapton Cu tape

  5. Test results from Bias circuit #4759 Bad Bias circuit from batch with some problem (SNs/4700-4899): Working with the scalpel it was possible to delaminate flaps of few mm size of the upper Kapton layer. The adhesion of the 2 layers is smaller than the adhesion to the tape. Flaps

  6. Test results from Bias circuit #4969 Bad Bias circuit from current batch: Working with the scalpel it was possible to delaminate flaps of several mm size of the upper Kapton layer. The delamination stops at the Cu layer: very similar to the defective trays. The adhesion of the 2 layers is very poor: when the edge of the scalpel in inserted between the layers, the delamination propagates by itself.

  7. Conclusion • We cannot use Bias circuits with S/N > 4700 • We ask urgent production of new bias circuits – we can cover up to tower 7 tray production with other bias circuits currently in Plyform • We will send back the whole batches 47xx and 49xx for test

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