Research Papers

Ohmic Curing of Three-Dimensional Printed Silver Interconnects for Structural Electronics

[+] Author and Article Information
David A. Roberson

W. M. Keck Center for 3D Innovation,
The University of Texas at El Paso,
El Paso, TX 79968
e-mail: droberson@utep.edu

Ryan B. Wicker, Eric MacDonald

W. M. Keck Center for 3D Innovation,
The University of Texas at El Paso,
El Paso, TX 79968

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received May 15, 2013; final manuscript received March 30, 2015; published online April 17, 2015. Assoc. Editor: Paul Conway.

J. Electron. Packag 137(3), 031004 (Sep 01, 2015) (8 pages) Paper No: EP-13-1041; doi: 10.1115/1.4030286 History: Received May 15, 2013; Revised March 30, 2015; Online April 17, 2015

Ohmic curing was utilized as a method to improve the conductivity of three-dimensional (3D) interconnects printed from silver-loaded conductive inks and pastes. The goal was to increase conductivity of the conductive path without inducing damage to the substrate. The 3D via/interconnect structure was routed within 3D polymeric substrates and had external and internal sections. The 3D structures were created by the additive manufacturing (AM) process of stereolithography (SL) and were designed to replicate manufacturing situations which are common in the fabrication of 3D structural electronics that involve a combination of AM and direct write (DW) processing steps. The photocurable resins the 3D substrates were made of possessed glass transition temperatures of 75 °C and 42 °C meaning that a nonthermal method to increase the conductivity of the printed traces was needed as the conductive inks tested in this study required oven cure temperatures greater than 100 °C to perform properly. Ohmic curing was shown to decrease the measured resistance of the via/interconnect structure without harming the substrate. Substrate damage was observed on thermally cured samples and was characterized by discoloration and scaling of the substrate. Resistance measurements of the via/interconnect structures revealed samples cured by the ohmic curing process performed equal or better than samples subjected to thermal curing. The work presented here demonstrates a method to overcome the thermal cure temperature limitations of polymeric substrates imposed on the processing parameters of conductive inks during the fabrication of 3D structural electronics and presents an example of overcoming a manufacturing process problem associated with this emerging technology. An ink selection process involving characterization of the compatibility of inks with the substrate material and the use of different inks for the via and interconnect sections was also discussed.

Copyright © 2015 by ASME
Your Session has timed out. Please sign back in to continue.


Cano, J. L. C., 2011, “The Cambrian Explosion of Popular 3D Printing,” IJIMAI, 1(4), pp. 30–32. [CrossRef]
Pearce, J. M., Blair, C. M., Laciak, K. J., Andrews, R., Nosrat, A., and Zelenika-Zovko, I., 2010, “3-D Printing of Open Source Appropriate Technologies for Self-Directed Sustainable Development,” J. Sustainable Dev., 3(4), pp. 17–29. [CrossRef]
Malone, E., and Lipson, H., 2007, “Fab@Home: The Personal Desktop Fabricator Kit,” Rapid Prototyping J., 13(4), pp. 245–255. [CrossRef]
Roberson, D. A., Espalin, D., and Wicker, R. B., 2013, “3D Printer Selection: A Decision-Making Evaluation and Ranking Model,” Virtual Phys. Prototyping, 8(3), pp. 201–212. [CrossRef]
Whadcock, I., 2013,“A Third Industrial Revolution,” The Economist (online), accessed: Apr. 9, 2013, http://www.economist.com/node/21552901
Berman, B., 2012, “3-D Printing: The New Industrial Revolution,” Bus. Horiz., 55(2), pp. 155–162. [CrossRef]
Valero-Gomez, A., Gonzalez-Gomez, J., Gonzalez-Pacheco, V., and Salichs, M. A., 2012, “Printable Creativity in Plastic Valley UC3M,” IEEE Global Engineering Education Conference (EDUCON), Marrakech, Morocco, Apr. 17–20 [CrossRef].
Gonzalez-Gomez, J., Valero-Gomez, A., Prieto-Moreno, A., and Abderrahim, M., 2012, “A New Open Source 3D-Printable Mobile Robotic Platform for Education,” Advances in Autonomous Mini Robots, U.Rückert, S.Joaquin, and W.Felix, eds., Springer, Berlin, pp. 49–62.
Schmidt, A., Doring, T., and Sylvester, A., 2011, “Changing How We Make and Deliver Smart Devices: When Can I Print Out My New Phone?,” IEEE Pervasive Comput., 10(4), pp. 6–9. [CrossRef]
Kim, N.-S., and Han, K. N., 2010, “Future Direction of Direct Writing,” J. Appl. Phys., 108(10), p. 102801. [CrossRef]
Mancosu, R. D., Quintero, J. A. Q., and Azevedo, R. E. S., 2010, “Sintering, in Different Temperatures, of Traces of Silver Printed in Flexible Surfaces,” 11th International Conference on Thermal, Mechanical & Multi-Physics Simulation, and Experiments in Microelectronics and Microsystems (EuroSimE), Bordeaux, France, Apr. 26–28. [CrossRef]
Ko, S. H., Pan, H., Grigoropoulos, C. P., Luscombe, C. K., Fréchet, J. M. J., and Poulikakos, D., 2007, “All-Inkjet-Printed Flexible Electronics Fabrication on a Polymer Substrate by Low-Temperature High-Resolution Selective Laser Sintering of Metal Nanoparticles,” Nanotechnology, 18(34), p. 345202. [CrossRef]
Huang, D., Liao, F., Molesa, S., Redinger, D., and Subramanian, V., 2003, “Plastic-Compatible Low Resistance Printable Gold Nanoparticle Conductors for Flexible Electronics,” J. Electrochem. Soc., 150(7), pp. G412–G417. [CrossRef]
Jang, S., Seo, Y., Choi, J., Kim, T., Cho, J., Kim, S., and Kim, D., 2010, “Sintering of Inkjet Printed Copper Nanoparticles for Flexible Electronics,” Scr. Mater., 62(5), pp. 258–261. [CrossRef]
Li, Y., Wu, Y., and Ong, B. S., 2005, “Facile Synthesis of Silver Nanoparticles Useful for Fabrication of High-Conductivity Elements for Printed Electronics,” J. Am. Chem. Soc., 127(10), pp. 3266–3267. [CrossRef] [PubMed]
Russo, A., Ahn, B. Y., Adams, J. J., Duoss, E. B., Bernhard, J. T., and Lewis, J. A., 2011, “Pen-On-Paper Flexible Electronics,” Adv. Mater., 23(30), pp. 3426–3430. [CrossRef] [PubMed]
Hu, J., 2010, “Overview of Flexible Electronics From ITRI's Viewpoint,” 28th VLSI Test Symposium (VTS), Santa Cruz, CA, Apr. 19–22, pp. 84 [CrossRef].
Roberson, D., MacDonald, E., Church, K., and Wicker, R., 2010, “Failure Investigation of Direct Write Pen Tips,” J. Failure Anal. Prev., 10(6), pp. 504–507. [CrossRef]
Roberson, D. A., Wicker, R. B., and MacDonald, E., 2012, “Microstructural Characterization of Electrically Failed Conductive Traces Printed From Ag Nanoparticle Inks,” Mater. Lett., 76, pp. 51–54. [CrossRef]
Hoffman, J., Hwang, S., Ortega, A., Kim, N.-S., and Moon, K., 2013, “The Standardization of Printable Materials and Direct Writing Systems,” ASME J. Electron. Packag., 135(1), p. 011006. [CrossRef]
Tobjörk, D., Kaihovirta, N. J., Mäkelä, T., Pettersson, F. S., and Österbacka, R., 2008, “All-Printed Low-Voltage Organic Transistors,” Org. Electron., 9(6), pp. 931–935. [CrossRef]
Church, K., MacDonald, E., Clark, P., Taylor, R., Paul, D., Stone, K., Wilhelm, M., Medina, F., Lyke, J., and Wicker, R., 2009, “Printed Electronic Processes for Flexible Hybrid Circuits and Antennas,” Flexible Electronics & Displays Conference and Exhibition, Phoenix, AZ, Feb. 2–5. [CrossRef]
Lopes, A. J., MacDonald, E., and Wicker, R. B., 2012, “Integrating Stereolithography and Direct Print Technologies for 3D Structural Electronics Fabrication,” Rapid Prototyping J., 18(2), pp. 129–143. [CrossRef]
Wicker, R. B., and MacDonald, E. W., 2012, “Multi-Material, Multi-Technology Stereolithography,” Virtual Phys. Prototyping, 7(3), pp. 181–194. [CrossRef]
Navarrete, M., Lopes, A., Acuna, J., Estrada, R., MacDonald, E., Palmer, J., and Wicker, R., 2007, “Integrated Layered Manufacturing of a Novel Wireless Motion Sensor System With GPS,” 18th Annual Solid Freeform Fabrication Symposium, Austin, TX, Aug. 6–10, pp. 575–585. http://sffsymposium.engr.utexas.edu/Manuscripts/2007/2007-49-Wicker.pdf
Castillo, S., Muse, D., Medina, F., MacDonald., Wicker, R., 2009, “Electronics Integration in Conformal Substrates With Additive Layered Manufacturing,” 20th Annual Solid Freeform Fabrication Symposium, Austin, TX, Aug. 3–5, pp. 730–737. http://sffsymposium.engr.utexas.edu/Manuscripts/2009/2009-63-Castillo.pdf
DeNava, E., Navarrete, M., Lopes, A., Alawneh, M., Contreras, M., Muse, D., Castillo, S., MacDonald, E., and Wicker, R., 2008, “Three-Dimensional Off-Axis Component Placement and Routing for Electronics Integration Using Solid Freeform Fabrication,” 19th Annual Solid Freeform Fabrication Symposium, Austin, TX, Aug. 4–6, pp. 362–369. http://sffsymposium.engr.utexas.edu/Manuscripts/2008/2008-33-DeNava.pdf
Roberson, D. A., Wicker, R. B., Murr, L. E., Church, K., and MacDonald, E., 2011, “Microstructural and Process Characterization of Conductive Traces Printed From Ag Particulate Inks,” Materials, 4(6), pp. 963–979. [CrossRef]
Greer, J. R., and Street, R. A., 2007, “Thermal Cure Effects on Electrical Performance of Nanoparticle Silver Inks,” Acta Mater., 55(18), pp. 6345–6349. [CrossRef]
Saraf, R. F., Roldan, J. M., Jagannathan, R., Sambucetti, C., Marino, J., and Jahnes, C., 1995, “Polymer/Metal Composite for Interconnection Technology,” 45th Electronic Components and Technology Conference (ECTC), Las Vegas, NV, May 21–24, pp. 1051–1053. [CrossRef]
Kim, D., and Moon, J., 2005, “Highly Conductive Ink Jet Printed Films of Nanosilver Particles for Printable Electronics,” Electrochem. Solid-State Lett., 8(11), pp. J30–J33. [CrossRef]
DSM Somos®, ProtoTherm™ 12120 Product Data Sheet, 2012, DSM Somos®, Elgin, IL.
DSM Somos® WaterShed™ 11120 Product Data Sheet 2012, DSM Somos®, Elgin, IL.
Lopes, A. J., Lee, I. H., MacDonald, E., Quintana, R., and Wicker, R., 2014, “Laser Curing of Silver-Based Conductive Inks for In Situ 3D Structural Electronics Fabrication in Stereolithography,” J. Mater. Process. Technol., 214(9), pp. 1935–1945. [CrossRef]
Choi, J. H., Ryu, K., Park, K., and Moon, S.-J., 2015, “Thermal Conductivity Estimation of Inkjet-Printed Silver Nanoparticle Ink During Continuous Wave Laser Sintering,” Int. J. Heat Mass Transfer, 85, pp. 904–909. [CrossRef]
Roberson, D. A., 2012, “A Novel Method for the Curing of Metal Particle Loaded Conductive Inks and Pastes,” Ph.D. dissertation, Materials Science and Engineering, The University of Texas at El Paso, El Paso, TX.
Roberson, D. A., Wicker, R. B., and MacDonald, E., 2012, “Ohmic Curing of Printed Silver Conductive Traces,” J. Electron. Mater., 41(9), pp. 2553–2566. [CrossRef]
Allen, M. L., Aronniemi, M., Mattila, T., Alastalo, A., Ojanperä, K., Suhonen, M., and Seppä, H., 2008, “Electrical Sintering of Nanoparticle Structures,” Nanotechnology, 19(17), p. 175201. [CrossRef] [PubMed]
Lopes, A. J., Navarrete, M., Medina, F., Palmer, J. A., MacDonald, E., and Wicker, R. B., 2006, “Expanding Rapid Prototyping for Electronic Systems Integration of Arbitrary Form,” 17th Annual Solid Freeform Fabrication Symposium, University of Texas at Austin, Austin, TX, Aug. 14–16, pp. 644–655. http://sffsymposium.engr.utexas.edu/Manuscripts/2006/2006-56-Lopes.pdf
Olivas, R. I., 2011, “Conformal Electronics Manufacturing Through Additive Manufacturing and Micro-Dispensing,” M.S. thesis, Department of Electrical and Computer Engineering, The University of Texas at El Paso, El Paso, TX.


Grahic Jump Location
Fig. 1

The test structure used in this study which featured internal vias and external interconnects

Grahic Jump Location
Fig. 2

Examples of the process issues encountered when attempting to use DuPont CB028 ink on 3D structures: (a) dewetting of the ink in the via structure of a ProtoTherm™ structure; (b) ejection of the ink during the thermal curing process in a WaterShed™ structure; and (c) dewetting of the ink in the via portion of a WaterShed™ structure

Grahic Jump Location
Fig. 3

(a) Schematic of the scaffold support used to facilitate the 3D printing of complex geometries. (b) Photographs showing an example of the “scaling” substrate damage imposed by curing a ProtoTherm™ structure for 30 min at 138 °C on a substrate built on a scaffold support compared with a substrate cured at the same temperature, built on a polycarbonate sheet. Note the lack of scaling on the substrate built without a scaffold support.

Grahic Jump Location
Fig. 4

(a) Photograph of experiments where E1660 was used as vias and interconnects on ProtoTherm™ substrates and (b) the graphical results. Placement of the samples in the photographs corresponds with identifiers in the graphical results.

Grahic Jump Location
Fig. 5

(a) Photograph of experiments where CB102 used as vias and E1660 used as interconnects on ProtoTherm™ substrates and (b) the graphical results. Placement of the samples in the photographs corresponds with identifiers in the graphical results.

Grahic Jump Location
Fig. 6

Resistance versus time plots for ohmic curing cycles carried out at increasing applied current values for the hybrid E1660/CB102 conductive path printed in ProtoTherm™ 3D structures

Grahic Jump Location
Fig. 7

(a) Photographs of experiments involving substrates that were 3D printed from WaterShed™. Note the yellowing of the substrates associated with thermal curing at temperatures above 46 °C and (b) graphical results of the thermal cure process. Placement of the samples in the photographs corresponds with identifiers in the graphical results.

Grahic Jump Location
Fig. 8

(a) Photographs of experiments involving WaterShed™ substrates where E1660 used to print interconnects and CB102 was used to print vias and (b) graphical results of the thermal and ohmic cure processing. Placement of the samples in the photographs corresponds with identifiers in the graphical results.

Grahic Jump Location
Fig. 9

Example of tailoring the applied current based on wattage to cure process outliers from the thermal precure process for (a) E1660 conductive trace printed in a ProtoTherm™ substrate and (b) combination E1660/CB102 conductive path printed in a WaterShed™ substrate

Grahic Jump Location
Fig. 10

Typical resistance versus time behavior for an ohmic curing cycle. The first cycle at a given applied current causes a sharp drop in resistance. The subsequent cycles are not able to cause further significant curing effect. In this case the applied current was 4 A.

Grahic Jump Location
Fig. 11

(a) Optical micrograph showing evidence of charring of DuPont CB102 in a ProtoTherm™ substrate and (b) backscatter SEM micrographs showing charring of DuPont CB102 near the via/interconnect interface of a dual E1660/CB102 interconnect/via structure on a WaterShed™ substrate




Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In