Microlamination

1
Microlamination

• B. K. Paul

2
Outline

• How do we make microchannel arrays?
• Patterning
• Laser Machining
• Chemical Etching
• Diffusion Bonding
• Microlamination Economics

3
Microreactor Specifications

• Operate at lt 100 C and lt 1 atm
• Corrosive environment
• Explosive reaction
• Small volume of resin
• Minimize dead spots
• 316L Stainless Steel
• 200 µm diameter channels
• Flow rates demand millions of channels
• ? Number Up

4
Number Up Channels
200 µm wide channels in 316L SS
header

• Channels
• 200 µm wide 100 µm deep
• 300 µm pitch
• Lamina (24 long x 12 wide)
• 1000 µchannels/lamina
• 300 µm thickness
• Double-sided etch

channels
Chemically etched lamina
5
Number Up Layers

• Straight-through flow
• Counter-flow for HX
• (if necessary)
• Device (12 stack)
• 1000 laminae
• 1 x 106 reactor µchannels

6
Number Up Devices
Bank of Microchannel Reactors (9 x 106
microchannels)
Microlamination of Reactor
7
MECS Fabrication

• Precision typically achieved with Silicon
• MECS are larger than IC/MEMS/µTAS
• MECS are high-throughput fluidic devices
• Silicon is generally not the favored base
  material
• Cost
• Properties

Courtesy of DOE ARC
10 x 10 x 20 cm HX
Courtesy of DOE PNNL
100 µm high microchannels
5 µm pores
8
Microlamination Paul et al. 1999, Ehrfeld et
al. 2000

• Bonding
• diffusion bonding
• solder paste reflow
• ultrasonic welding

• Registration
• thermally-enhanced edge registration
• compliant registration
• thermal compliance

• Patterning
• machining (laser )
• micromolding
• forming (punching )

W. Ehrfeld, V. Hessel, H. Löwe, Microreactors
New Technology for Modern Chemistry, Wiley-VCH,
2000.
9
Microlamination Paul et al. 1999, Ehrfeld et
al. 2000
Microchannel Array
Copper
Cross-section of SS Array
Micrograph courtesy of PNNL
W. Ehrfeld, V. Hessel, H. Löwe, Microreactors
New Technology for Modern Chemistry, Wiley-VCH,
2000.
10
Microchannel Arrays
65 x 130 µm
100 µm
Cu
150 µm
Al2O3
100 x 100 µm
316L SS
Ti
11
Microlamination Challenges

• Identical dimensions across 1E6 channels
• Silicon is generally not the favored base
  material
• High aspect ratio features
• Susceptible to warpage
• Embedded geometry
• Distribution of flow between layers and channels

35 µm high microchannels
microchannel warpage
header design
12
Outline

• How do we make microchannel arrays?
• Patterning
• Chemical Etching
• Laser Machining
• Diffusion Bonding
• Microlamination Economics

13
Microlamination
14
Metal Patterning

• Through cut
• Laser Machining
• Wire Electrical Discharge Machining
• Sheet Metal Punching/Blanking
• Blind cut
• Micro Electrical Discharge Machining
• Photochemical Machining
• Sheet Metal Drawing

15
Laser Machining
UPE membrane
20 µm hole arrays
16
Wire EDM
17
microEDM
Spindle
Collet

• Tool wear is a key concern and makes this
  technique difficult to produce more than one
  lamina.
• Better for adding features to tooling.

Tool
MicroEDM
18
Photochemical Machining
19
Sheet Metal FormingBlanking/Punching
20
Sheet Metal FormingDrawing
21
Outline

• How do we make microchannel arrays?
• Patterning
• Chemical Etching
• Laser Machining
• Diffusion Bonding
• Microlamination Economics

22
Photochemical Machining
23
Designers Perspective
24
Manufacturers Perspective

• Etch factor, E
• where
• U undercut
• d etch depth
• Anisotropy, A
• Mask width, Wm
• where
• Wf feature width

NOTE Etch factor in readings is not same.
25
Outline

• How do we make microchannel arrays?
• Patterning
• Chemical Etching
• Laser Machining
• Diffusion Bonding
• Microlamination Economics