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

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

What is MIM?

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

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

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

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

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

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

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

Post-Sintering Structure 3000x Magnification

CNC Machining and Plating MIM tolerances +/- 0.5% For features <4.0 mm it is +/- 0.02 mm CNC tolerances +/- 15 µm Plating Gold Nickel Other

MIM Materials: Kovar® Photonic and optoelectronics packages which match CTE of borosilicate glass 29% W, 17% Co, 53% Fe Properties CTE (30-400oC) 4.4-5.2 ppm/ oC Density – 7.95 g/cm3 % Density – 97%

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%

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 – 14.89 g/cm3 % Density - 95%

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

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

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 ►

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 ►

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

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

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

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