Slide 1Susanne KyreTracker week, October 2005 TEC/TOB bias bonds Susanne Kyre University of California, Santa Barbara

Slide 2Susanne KyreTracker week, October 2005 TEC/TOB bias bonds Wirebonds will be added to the back of all TEC and TOB modules to add redundancy to the bias connection On TOB modules a bondable tab needs to be added to the module frame New modules Existing modules are retrofitted (~2600 modules) TEC modules already have a gold plated area on the module frame, where wirebonds can be placed All bias bonds get encapsulated to protect them from damage during handling

Slide 3Susanne KyreTracker week, October 2005 New TOB modules Two small tabs (gold plated kapton) are soldered to the module frame During module assembly the tabs are glued to the back side of the sensor

Slide 4Susanne KyreTracker week, October 2005 Existing TOB modules I For modules that have little or no silver epoxy under the the gold plated hole in the kapton of the module frame, a small tab (gold plated kapton) gets glued with silver epoxy to the gold The tab is also glued to the sensor Most of the 1200 modules at UCSB will be retrofitted using this method

Slide 5Susanne KyreTracker week, October 2005 Existing TOB modules II For modules that have a lot of silver epoxy under the gold plated hole in the kapton of the module frame, a wire is soldered to the resistor on front side of the module The wire gets looped around the edge of the frame to the back side A small tab (gold plated kapton), which has previously been soldered to the wire, gets glued to the sensors straddling the gap between the sensors All 1400 FNAL modules and about 80 UCSB modules will be retrofitted using this method

Slide 6Susanne KyreTracker week, October 2005 Bias wirebonding Height requirement: Maximum encapsulant height must be below the highest point on the module frame Wirebond loop height is kept to 280 microns Encapsulant height is kept below 630 microns After the front side of the module is wirebonded, the module gets removed from the module carrier, turned over and placed on a special vacuum fixture 15 wire bonds are placed on each of the 2 bias bond areas on the backside of the modules

Slide 7Susanne KyreTracker week, October 2005 Bias bond encapsulation For the detailed procedure see: For the drawings of UCSB designed tools see:

Slide 8Susanne KyreTracker week, October 2005 Material and Preparation Sylgard 186 Silicone Elastomer, 2 part kit, 10:1 mixing ratio (manufacturer: Dow- Corning) Mixing cups Mixing sticks Digital bench scale Small vacuum chamber or centrifuge for degassing

Slide 9Susanne KyreTracker week, October 2005 Dispensing Equipment Pneumatic glue dispenser with foot pedal and timed pulse option (manufacturer: EFD model: Ultra 1400) 3ccm syringe barrel and piston (EFD) Smooth-flow tapered tips, gage 20 (EFD)

Slide 10Susanne KyreTracker week, October 2005 Set up Equipment Base plate (UCSB design), to hold the module on a module carrier upside down Plastic trowel (UCSB design), to spread the encapsulant over the wirebonds and to keep the height of the encapsulant below the maximum height Stereo microscope (optional)

Slide 11Susanne KyreTracker week, October 2005 Procedure I Mix encapsulant, degas the mixture and fill syringe Set pneumatic dispenser to 15 psi and 1 second dispense time Set module in carrier upside down onto base plate Dispense a line of encapsulant across the width of the wirebonds

Slide 12Susanne KyreTracker week, October 2005 Procedure II Position the trowel with one leg on the sensor, one leg on the kapton Spread the encapsulant over all 15 wirebonds by sliding the trowel across the bonds Once the trowel is past the wirebonds, lift it up and clean it off with a dry tissue paper

Slide 13Susanne KyreTracker week, October 2005 Procedure III Check that all wirebonds are covered completely with the encapsulant (this can be done with or without a stereo microscope) If necessary apply more silicone and repeat the troweling procedure Cure for 24 hours with the backside of the module facing up to avoid beading up of the encapsulant