Question

JCL Inc. is a major chip manufacturing firm that sells its products to computer manufacturers like Dell, HP, and others. In simplified terms, chip making at JCL Inc. involves three basic operations: depositing, patterning, and etching.

• Depositing: Using chemical vapor deposition (CVD) technology, an insulating material is deposited on the wafer surface, forming a thin layer of solid material on the chip.
• Patterning: Photolithography projects a microscopic circuit pattern on the wafer surface, which has a light-sensitive chemical like the emulsion on photographic film. It is repeated many times as each layer of the chip is built.
• Etching: Etching removes selected material from the chip surface to create the device structures.

The following table lists the required processing times and setup times at each of the steps. Assume that the unit of production is a wafer, from which individual chips are cut at a later stage.

Note: A setup can only begin once the batch has arrived at the machine.

Process Step	1 Depositing	2 Patterning	3 Etching
Setup time	58 min.	26 min.	16 min.
Processing time	0.21 min./unit	0.31 min./unit	0.26 min./unit

(a) What is the process capacity in units per hour with a batch size of 100 wafers?

Answered in a table like:

Deposition units/hr

Patterning units/hr

Etching units/hr

(c) Suppose JCL Inc. came up with a new technology that eliminated the setup time for step 1 (deposition), but increased the processing time to 0.58 minute/unit. What would be the batch size you would choose so as to maximize the overall capacity of the process? (Round your intermediate computations to 2 decimal places. Round your final answer to the nearest whole number.)

Batch size is ___ units?

Answer 1

JCL Inc
process step	1. depositing	2. patterning	3. etching
setup time (min)	58	26	16
processing time (m/unit)	0.21	0.31	0.26
capacity = batch size/(setup time + batch processing time)
a. batch size	100	wafers
step	capacity (unit/min)	capacity (unit/hour)
1. depositing	1.3	76
2. patterning	1.8	105
3. etching	2.4	143
b.
process step	1. depositing
setup time (min)	0
processing time (m/unit)	0.58
process capacity	1.724137931	units/min
this is the maximum process capacity.
to achieve this capacity, step 1 has to be the bottleneck, hence:
for batch size B:
B/(26+0.31B)>=1.72	(Data for step b. patterning)
1.72*(26+0.31B)<=B
44.83+0.53B<=B
44.83<=(1-0.53)B
44.83<=0.47B
B>=96.3 units
hence, to maximize the overall capacity of the process, the Batch size is 96 units.

formula used: