# Homework Help: Glass crack on Aluminum and Copper tungsten

1. Sep 1, 2014

### andy203

1. The problem statement, all variables and given/known data

Here is the issue I met.Could you refer to attached file?

1.We glued one piece aluminum block and one piece copper tungsten block on substrate.
The aluminum and copper tungsten block have different height.The glue thickness underneath them
is different.
2.Then,we glued one piece glass on aluminum block and copper tungsten block.

3.However,after 120°C storage for overnight,we found crack as marked in the red.
We suspect the crack is due to thermal strain/stress.
4.We want to find a way to calculate the thermal strain/stress on the glass.

Here are some information that I can provide at this moment.

Glass material Silicon: 2.6X10E-6/°C
Copper tungsten:CuW, 6.5X10E-6/°C
Aluminum: 22X10E-6/°C
Glue20E epoxy CTE ,31X10E-6 /°C
Substrate:AlN 5.3X10E-6/°C

2. Relevant equations

ΔL=κ∇T.

3. The attempt at a solution

I am trying to use solidworks to simulate this design.The most hard thing for me is to define the glue property.Since the height of aluminum and copper tungsten is different.

Highly appreciated if any one can give me some help.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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