1

Short update

Itzhak Tserruya

HBD meeting BNL, April 11, 2006

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Update on the PCB production• There were problems at each of the three production steps (drilling, plating, etching) and three production cycles were needed before one full cycle could be completed. This happened on March 30.

•Ilia traveled to Geneva and brought the PCB to WI on March 31.

•A thorough check of the PCB revealed two problems:

-172 holes (app. 15%) were not plated-through

- app. 50% of the holes for the pins to support the GEMs were not at the correct place. We could mount the pins of three panels only, the rest was increasingly off (maximum deviation is of the order of 1 mm)

• A thorough comparison with the PCBs that failed in the previous cycles revealed that the material suffers some contraction mainly during the plating process but also during etching.

• CERN is producing a new PCB introducing a scaling factor in the drilling that will hopefully compensate for the contraction.

•In the meantime we have developed the tools and means to repair the existing PCB, in case that this new cycle would turn out to fail again.

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Hole mismatch

Bottom middle Bottom Right

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Mesh Electrode: Stretching

• The mesh is carefully aligned along one of the bars and then clamped.

• A similar alignment is done on an adjacent side.

• The other two sides are then usually properly aligned.

• The mesh is stretched by turning the screws. A reproducible tension of 6N/cm (± 10%) is achieved by 1.5 turn of each screw.

• With such a tension the mesh deforms by less than when a 1000 V are applied to the mesh against a flat ground plate.

stretching device

stretching completed

clamping

alignment

5

Mesh Electrode:Gluing

• The frame is positioned with pins on a supporting plate

•A glue dispenser is used to apply a uniform layer of glue 200 micron thick over 4mm of the frame (5mm width)

• The regular glue is replaced by conductive glue at the foreseen location of the HV contact .

• The frame with glue is positioned below the stretched mesh and lifted till the mesh is well embedded under the glue

• After curing, the mesh is carefully cut first outside and then on the mesh, and the edges are covered with glue.

gluing device

Glue dispenser

Gluing mesh to frame

Conductive glue

6

Mesh Electrode:Cutting

• After curing, the mesh is carefully cut first outside, and later on the frame.

• The edges of the mesh along the frame and close to the holes are covered with glue.

• Once released from the pins, the mesh electrode is deformed under the mesh tension. This is normal. The flatness is restored when mounting the electrode on the pins supporting the whole detector module.

Mesh protection during cutting

Electrode deforms once released from the pins