MCEN5228-011/4228-011: Microsystems Integration

Homework #7, Due Date: Friday, March 17

The Word file of the homework is posted on the class web site. Email your PDF or Word file with answers to before the class on the 17th. There is a penalty, e.g. 5 to 25 points, for late submission.

Name: ______, Email: ______

1.  (15 points) Please answer the following questions on ALD and MLD. A one-paragraph answer to each question is good enough.

·  Can we achieve ALD if we do not remove the precursors in the deposition chamber?

·  ALD Al2O3, TiO2 and SiO2 are hydrophilic coatings. Why do we want to apply such hydrophilic coatings over a hydrophobic polymer substrate for the polymer thermal ground plane?

·  What’s the difference between ALD and MLD?

·  The MLD illustrated by the Nylon 66 processes would produce a defective coating. Why?

·  Why do we want to apply multiple, inorganic/organic layers to encapsulate polymer substrates?

2.  (10 points) CU Boulder faculty and students have developed three enabling technologies for future microsystems represented by the 1-mm thin smartphone discussed in the class. Please propose an application that will benefit significantly from such a thin and flexible solution. Of course, you should not propose a smartphone since it was covered in the lecture.

3.  (10 points) We can use finite element method (FEM) simulations to calculate stresses/strains and apply inelastic strain energy to predict solder fatigue lives w.r.t. different effects. Please use the slides presented to identify three effects that are not covered by the simple Coffin Mason relationships. An example of the answer is illustrated as follows: the CTE local mismatch effect could not be simulated using this approach. As shown in the slide #13, the fatigue life is 5,337 cycles when both global and local mismatches are considered. It becomes 6,990 when only the local mismatch is considered. Such an effect could not be studied using the simple Coffin Mason relationship.

4.  (5 points) The PEEQ (equivalent plastic strain) distribution of a solder joint during thermal cycling are shown below. High PEEQs are at the interface between the solder joint and the upper substrate. Why? Give us a one-paragraph explanation.

5.  (10 points) In the study on the laser module, an experiment and three FEM simulations were conducted. Please use the slide numbers to identify the three FEM simulations. Use a short paragraph to describe each case of simulation. We should pay attention to an important feature of the three FEM models. What is this feature?