1. Metal Injection Molded Photonic Device Packaging
Rob Linke
MIMforms LLC 1 1

2. Outline Metal injection molding defined Manufacturing process
Materials for photonics packaging
Benefits of metal injection molding
Future directions
Conclusions and resources

3. What is MIM?

4. Metal Injection Molding
Utilizes wealth of technology developed for plastic injection molding
Injection molding of metal powder compounded with binder (plastic/wax)
Debinding of component (solvent or thermal)
Sintering of part to final density 2 2

5. Manufacturing Process
Design of Component
Tooling of Mold
Injection Molding
Debinding
Sintering
Optional CNC Machining
Finishing/Plating

6. Compounding Components Goals Metal powder Wax Polymers
Sufficient binder to fill all voids
Uniform mixture
Metal powder at 100x
D50 : 2-10 µm

7. Injection Molding Virtually identical to plastic injection molding
“Feedstock” is molded at low temperatures (150oC) with consistency of toothpaste
Consists of metal powder in binder matrix (~ 40% binder by volume)
Yields “green” part

8. Debinding Binder removal from matrix (disposable component)
Solvent – water or other solvent
Thermal decomposition
Results in structurally weak component with small amount of binder remaining

9. Sintering
Sintering densification increases the atomic bonds between particles
Temperature is near melting point
Density of up to 98.5%
Real world example – ice cubes sticking together in freezer
Sintering Furnace

10. Shrinkage in Sintering
Green part typically shrinks 15% during sintering
Density increases
Strength increases
Final mechanical properties attained

11. Post-Sintering Structure
3000x Magnification

12. CNC Machining and Plating
MIM tolerances
+/- 0.5%
For features <4.0 mm it is +/ mm
CNC tolerances
+/- 15 µm
Plating
Gold
Nickel
Other

13. MIM Materials: Kovar®
Photonic and optoelectronics packages which match CTE of borosilicate glass
29% W, 17% Co, 53% Fe
Properties
CTE (30-400oC) ppm/ oC
Density – 7.95 g/cm3
% Density – 97%

14. MIM Materials: Iron-Nickel
Photonic and optoelectronics packages
50% Fe, 50% Ni
Properties
CTE – 8.8 ppm/ oC
Density – 7.75 g/cm3
% Density - 95%

15. MIM Materials: Tungsten-Copper
Heatsinks for photonic housings which mirror CTE of borosilicate glass
80%W, 20% Cu as Example
Properties
CTE – 7.4 ppm/ oC at 50oC
Themal Conductivity – 189 W/m K
Density – g/cm3
% Density - 95%

16. Tungsten Copper Structures
Infiltrated Tungsten skeleton with liquid Copper
Vacuum Sintered Tungsten-Copper powder

17. Why use MIM? Reduce or eliminate individual CNC machining
Reduce material waste
Enable mass production of intricate, highly detailed structures
Reduce total cost
Kovar Lens Holder

18. Machine Once or Many? CNC machining MIM
Each part is machined to final shape individually
MIM
The mold is machined once and parts are molded to final shape
CNC
MIM
package cost ►
production volume ►

19. Shape Complexity CNC machining MIM Each detail adds to cost (and time)
Details are machined into the mold – once
Reproduced in each package during molding
CNC
MIM
package cost ►
shape complexity ►

20. Material Waste Reduction
CNC removes large amounts of metal to yield housing
MIM uses only metal necessary
75% waste reduction typical
Runners, gates can be recycled on-site
Material waste with CNC Machining

21. Future Directions Complex designs specifically for MIM manufacturing
Custom MIM alloys/mixtures
Higher dimensional tolerance MIM components
Increasing adoption of MIM package use in North America

22. Conclusions
MIM can be an enabling technology for photonic and optoelectronic packaging
Mass production
Low/no cost structures
Reduced material waste
Designs not possible or economical with CNC machining
Greater alloy flexibility through batch compounding

23. Additional Information on MIM
Organization:
CISP-Center for Innovative Sintered Products-Penn State
Book:
Injection Molding of Metals and Ceramics German & Bose