LBNL CCD Packaging “Yale Mount” Mechanical Analysis Dan Cheng LBNL

4/19/2003Dan Cheng2 First Guess for SNAP 1.4mm thick AlN substrate with 200  m via’s, not under bumps or CCD CCD, 200  m thick Gold bump (flattened wire bond bump) applied in house Underfill with Epotek glue at 60 o C Gold plated Invar Connector mounted to Invar with spring loaded pins against AlN AlN circuits from COORS Bumps on AlN applied at 4” wafer size level then diced No success yet in wafer scale bump bonds with AlN… dicing leaves large chips on edges

4/19/2003Dan Cheng3 Yale CCD Mount

4/19/2003Dan Cheng4 Solid Model Geometry (Pro/E) Rear View Front View

4/19/2003Dan Cheng5 Quarter-Symmetry Solid Model CCD (200 microns thick) Substrate (1.5-mm thick AlN Or 2-mm thick Si) EA9361 Epoxy (250 microns thick) Molybdenum Base (~5-mm thick) EPO-TEK (50 microns thick)

4/19/2003Dan Cheng6 Finite Element Mesh

4/19/2003Dan Cheng7 FEA Notes Quarter-symmetry model —Approximately 80,000 elements Symmetric boundary constraints —X- and Y- symmetry planes fixed, allowed to “slide” —Z-symmetry plane about square hole fixed in Z-direction Most material properties are temperature-dependent —With the exception of some Young’s Modulus numbers

4/19/2003Dan Cheng8 FEA Assumptions Mounting holes —Assumed constraints—see previous slide Did not model Gold/Indium bump bonds

4/19/2003Dan Cheng9 FEA Notes Ran four cases —Case 1: AlN Substrate, Square hole —Case 2: Si Substrate, Square hole —Case 3: AlN Substrate, Square hole w/Fillets —Case 4: Si Substrate, Square hole w/Fillets

4/19/2003Dan Cheng10 FEA Epo-Tek Stress Contour Plot

4/19/2003Dan Cheng11 FEA AlN Substrate Results Case 1, ALN Substrate, Square Hole Max Z Displacement 24 micronsAt corner edge Max VM Stress347 MPa ~50 ksi Corner of square hole in Moly CCD Max Stress26 MPa 3.7 ksi Max. Substrate Stress 51 MPa 7.4 ksi EA9361 Joint37 MPa 5.4 ksi Closer to Mpa average (2.7 ksi) Epo-Tek Joint7.5 MPa 1.1 ksi Bending shear*

4/19/2003Dan Cheng12 FEA Si Substrate Results Case 2, ALN Substrate, Square Hole Max Z Displacement 28 micronsAt corner edge Max VM Stress325 MPa ~47 ksi Corner of square hole in Moly CCD Max Stress17 MPa 2.5 ksi Max. Substrate Stress 64 MPa 9.3 ksi EA9361 Joint36 MPa 5.4 ksi Closer to Mpa average (2.7 ksi) Epo-Tek Joint6.6 MPa.9 ksi Bending shear

4/19/2003Dan Cheng13 FEA AlN Substrate Results #2 Case 3, ALN Substrate, Square Hole with Fillets Max Z Displacement 25 micronsAt corner edge Max VM Stress305 MPa ~43 ksi Corner of square hole in Moly CCD Max Stress25 MPa 3.5 ksi Max. Substrate Stress 50 MPa 7.4 ksi EA9361 Joint34 MPa 4.9 ksi Closer to Mpa average (2.7 ksi) Epo-Tek Joint7.4 MPa 1 ksi Bending shear*

4/19/2003Dan Cheng14 FEA Si Substrate Results #2 Case 4, ALN Substrate, Square Hole with Fillets Max Z Displacement 30 micronsAt corner edge Max VM Stress276 MPa ~40 ksi Corner of square hole in Moly CCD Max Stress15 MPa 2.2 ksi Max. Substrate Stress 64 MPa 9.3 ksi EA9361 Joint35 MPa 5.4 ksi Closer to Mpa average (2.7 ksi) Epo-Tek Joint6.6 MPa.9 ksi Bending shear

4/19/2003Dan Cheng15 FEA Summary Some material properties need to be defined at operating temperature (140 K) Current design shows critical Epo-Tek joint at above Yield Stress of 926 psi (may change with model)