Additive Manufacturing Methods and Materials Requirements for the Fabrication

of 3DPrinted Hybrid Electronic Circuits

D. R. HinesLaboratory For Physical Sciences

College Park, MD, USAhines@lps.umd.edu

(L1) Thermal processing up to 250 ˚C.

(L2) Fabrication on flat surfaces.

(L3) Surface mounted electronic components.

Current

Fabrication

Limitations:

Needed

Fabrication

Improvements:

Develop Fabrication Methods for the Elimination

of Surface Mounted (SMT) Electrical Components for Electronic Circuit Fabrication.

Direct-Write Printing Limitations and Needed Improvements

Platform Demonstrators:• LPS Power Supply • LM Micro-Controller

(1) Identify & characterize ink materials that can be

processed at temperatures below 150 ˚C

without loss in performance.

(2) Develop printing methods for the fabrication of

circuits onto non-flat, 3D printed surfaces.

(3) Develop methods for integrating/embedding

components into circuits during fabrication.

Object:

1. Deposition rate Rpp > 0.001 mm3/sec with the ability to establish a desired rate.

2. > 3 hours stable deposition rate (DR < 10%) with no more than one purge per hour.

3. Feature sizes down to 20 μm and surface roughness (Dh)< 10% of layer thickness (h).

4. In-situ and/or post processing at temperatures < 150 ˚C.

5. Resistivity < 6×10−8 Ωm for conducting inks. Good electrical insulation for dielectric inks. Dimensional stability for structural inks.

6. Adhesion good enough to pass scotch tape test.

7. Also need automatic calculation of total Volume (V) and total Length (L) to be printed for a given print file (this allows determination of desired Deposition Rate (R) and print Speed (s) for the file).

Minimum Processability Requirements of Ink Materialsfor Direct-Write Manufacturing (related to AJ printing)

Design Requirement

LPS Power Supply Circuit - Single Room layout

List of main components:(a) Capacitors: 10 µF & 20 µF(b) Resistors: KΩ(c) Si IC chip: (d) Inductor: µH

64-Pin QFP µC

J-TAG

Conn

3V Battery

ON/OFF Switch

LED Display

Sensor

I/O

(+)

C1

LM Micro-Controller Circuit

List of main components:

(c) Capacitors: 0.1 µF (d) Resistors: 220Ω to 50KΩ

(a) LEDs(b) Si IC chip

LPS Power Supply

~1 mm

Circuitization:Aerosol-Jet Printed using

Ag-N Ink for Conducting Layers &

P-PI ink for Dielectric Layer

AJ Printed onto Polyimide coated SiO2/Si Substrate.

Processing temperature 255 °CComponents : Surface Mounted~(15 x 20) mm

13 Working Boards• Functional Test process (Room Temp)• 24 Hr ESS Temp Cycling• 96 Hr High temp Burn-in• Functional Test process (Room temp)

Over 4000 hrs of Thermal Cycling &Accelerated Life Testing

As Printed Circuitization

Populated Circuit

Input:5 Volts1 Amp

Requirements of Embedded/Integrated Components

Requirements:• Processing Temperature < 150

with no loss in material performance.

• Printed Circuitization (previously demonstrated).

• Printed Interconnects to Bare die IC chips with smooth transitions between different leveled surfaces.

• Resistors for 200 Ω to 160 K Ω

• Capacitors up to 20 µF (consider bare die Si-based caps).

• Inductors in the µH range with Q-factor > 10.

Line Pitch Pyramid

Examples of AJ Printed Structures with in-situ curing of UV-curable Polymer Ink

1mm

Tubes(black streak is felt marker note on back surface of glass subst.)

Note: aspect ratio for smallest cylinder Þ 2.8Cylinders

~1 mm Sq Base

5 mm long traces

Smooth transitions between components are expected to be

important and require -

1. Structural stability.2. Good adhesion.3. Good electrical insulation.

Substrate Surface Electronics Components

ElectricalInterconnect

Well formed fillets require –Known and Stable Ink Deposition Rate (R).

< R > R= R

Y. Gu et. al., Journal of Micromechanics and Microengineering, 27, 097001 (2017).

Requirements for Printed Interconnects

AJ Printed Interconnects-over-Fillets

1 mm fillet 375 um fillet

Y. Gu et. al., Advanced Materials Technologies, 2 (2017).

Fillet – edge on views

Bare Si IC Chip with AJ Printed Interconnects

LM µ-Controller Chip

Close up image of Interconnects-over-Fillets

100 µm

LM u-Controller Circuit with Integrated Bare Si IC Chip

as printed

after SMT component attach

10 mm

AJ Printed Resistors

PS Circuit with Si based Capacitors as Substrate

~(15 x 20) mm

3.3μF/sq

2. Interconnects & Jumpers

3. Original PSCS

1. 4X8 Caps Substrate

AJ Printed Inductors

Polymer-Core, Straight SolenoidPlanar-Spiral

Ferrite-Core Iron-Core

AJ Printed InductorsPolymer-Core, Tapered Solenoid

Simulated and measured Results of AJ Printed Inductors

! "#$%&'>! "(')*($+ > ! -&#)%)+./0 "#$%&' < ./0 "(')*($+ < ./0 -&#)%)+

234 = 128 9 : ;

Q-factorOperating Frequency

Summary of Embedded/Integrated Components for Electronic Circuit Fabrication.

ResultsComponent Material(s) Status

Circuitization AJ printed Ag ink & Polymer ink

DemonstratedIntegrated into PS & uC

tested (PS - TC & HTOL)

Resistors AJ printed Carbon based resistor paste

Demonstrated

Capacitors Si based 3.3 uF Capacitors DemonstratedWorking to integrate into PS

Inductors AJ printed Ag ink w/ polymercore

Demonstrated

Si Bare IC chips Interconnect electrical attach to 300 um thick

bare die

DemonstratedIntegrated into uC

Interconnects AJ printed Ag ink over polymer fillets

DemonstratedIntegrated into uC

Test sample - in TC testing

Summary of Demonstrated AJ Printed ComponentsCapacitor Substrate

Printed Resistors

Printed Solid-core Inductors

Printed Interconnects-over-Fillets with Bare Si IC chips