Evaluation of Coatings Applied to Flexible Substrates to ... - IEEE Xplore

342

IEEE TRANSACTIONS ON COMPONENTS, PACKAGING AND MANUFACTURING TECHNOLOGY, VOL. 2, NO. 2, FEBRUARY 2012

Evaluation of Coatings Applied to Flexible Substrates to Enhance Quality of Ink Jet Printed Silver Nano-Particle Structures Henrik Andersson, Cecilia Lidenmark, Thomas Öhlund, Jonas Örtegren, Anatoliy Manuilskiy, Sven Forsberg, and Hans-Erik Nilsson

Abstract— Different types of the commercial surface treatment InkAid have been evaluated as a surface treatment to enhance print quality of silver nano-particle ink structures printed on polyimide and polyethene substrates. Originally these coatings were designed to be applied on substrates for graphical ink jet printing. On the coated polyimide and polyethene substrates lines of different widths have been printed using a Dimatix materials printer together with silver nano-particle ink manufactured by Advanced Nano-Products. The prints have then been evaluated in terms of print quality and resistivity before and after sintering. The results show that the application of these coatings can improve the print quality considerably, making it possible to print lines with a good definition, which is not otherwise possible with this type of ink on this substrate types. It has been found that the semi-gloss coating provides the best results, both in terms of print quality as well as the lowest resistivity. The resistivity on polyethene is 3.5 × 10−7 m at best when sintered at 150 °C and for polyimide 8.9×10−8 m sintered at 200 °C. This corresponds to a conductivity of about 4.5% and 18% of bulk silver, respectively. It can be concluded that applying such polyvinylpyrrolidone (PVP)based coatings to polyethene and polyimide will increase the print quality quite substantially, making it possible to print patterns with requirements of smaller line widths and more details than what is possible without coating. Index Terms— Conductive ink, flexible printed circuits, nanoparticles.

I. I NTRODUCTION

T

HERE is a growing interest in printed electronics and functions manufactured on flexible substrates. One important aspect when manufacturing flexible electronics is to have reliable, low resistance interconnects between different components and the power source. This is particularly true

Manuscript received March 31, 2011; revised September 30, 2011; accepted November 8, 2011. Date of publication December 21, 2011; date of current version February 3, 2012. Recommended for publication by Associate Editor R. N. Das upon evaluation of reviewers’ comments. H. Andersson, A. Manuilskiy, and H.-E. Nilsson are with the Department of Information Technology and Media, Mid Sweden University, Sundsvall SE-851 70, Sweden (e-mail: [email protected]; [email protected]; [email protected]). C. Lidenmark and S. Forsberg are with the Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, Sundsvall SE-851 70, Sweden (e-mail: [email protected]; [email protected]). T. Öhlund and J. Örtegren are with the Department of Information Technology and Media, Mid Sweden University, Örnsköldsvik SE-891 18, Sweden (e-mail: [email protected]; [email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TCPMT.2011.2176125

as one of the benefits associated with printed electronics is their ability to cover a large area and the lengths of the interconnects can be considerably longer than those for traditional electronics. Depending on the application, the demands on the tracks could be different with some constructions requiring narrow tracks which are closely spaced and thus, in this case, it is important that the printing produces well-defined patterns. For other applications there is a greater concern in terms of the overall resistance and thus it becomes possible to have much wider tracks. Overall, the ability to print low resistivity interconnects with the best possible print quality on the substrate of choice should prove to be of general interest. Several print techniques have been used for printed electronics including screen printing and flexography, but ink jet has gained significant attention during recent years as a flexible manufacturing tool. Some of the benefits associated with ink jet include the fact that material is only deposited where it is required and that it is very easy to modify the patterns to be printed. There are many examples of electrical components and interconnects manufactured by ink jet and other printing techniques; a few are shown in [1]–[11]. One of the drawbacks associated with ink jet printing is that it is sometimes difficult to achieve good print quality with certain inks on certain substrates and this is generally due to the fact that the ink must be formulated within certain specifications in order to work with ink jet print heads. Some silver nano-particle inks result in better print quality than others on different substrates, both plastic and paper. The ink chosen here is not the only possible option, there are many others inks available, of which some will give a better print quality on uncoated substrates, for example Cabot silver nano ink. However, the investigation presented is motivated because sometimes there is a need to use a specific ink with substrates that does not give an optimal print quality when used uncoated. This could be because a certain ink must be used on a certain substrate or that an ink has certain specific properties such as low sintering temperature or special content. This means, primarily, that the viscosity must be substantially lower than for other printing techniques and that the particle size must be sufficiently small to be able to pass through the nozzles without clogging. Because the ink formulation is fixed within rather narrow boundaries, the solution could involve modifying or changing the substrate. This modification could involve the application of a coating or in changing

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ANDERSSON et al.: EVALUATION OF COATINGS APPLIED TO FLEXIBLE SUBSTRATES

the surface energy by means of corona, plasma or some other treatment [12]–[13]. Applying a coating will change the surface roughness, the surface energy and also possibly the porosity. This will have an effect on the ink spreading and absorption, and thus also on the setting and drying of the ink. In this paper, the commercial surface treatment InkAid has been evaluated as a coating in order to enhance the print quality of polyimide (brand name Kapton) and polyethene substrates on which silver nano-particle ink structures are printed. The main objective has been to achieve a higher print quality with better defined lines as compared to uncoated substrates. Polyimide has been chosen because it is commonly used for flexible electronics and can be used in relatively high temperatures and polyethene because it is an inexpensive substrate, although the drawback is that it cannot withstand higher temperatures. InkAid was originally specified in order to enhance surfaces for graphical ink jet printing and not specifically for metal particle inks. The line of InkAid products consists of several different formulations for different types of surfaces, such as porous and non-porous substrates. II. E XPERIMENT The ink used was the ANP DGP 40LT-15C silver ink which contains a polar solvent and a solid silver content of 40–45%. This ink is a nano-particle ink, in which the silver particles have a diameter of about 30 nm and it is surrounded by a polymer shell [14]. In order to obtain a good conductivity it is necessary for the silver particles to be sintered, which can be performed by thermal heating in an oven, by electric sintering or by other methods [15]–[20]. The curing temperature for this ink is stated by the manufacturer as falling within the range of 100–150 °C, although a higher temperature will increase the conductance toward some maximum obtainable conductance. Two different types of InkAid have been evaluated, Clear Semi Gloss Precoat (hereafter abbreviated to Coating A) that is specified to be generally used on both porous and nonporous media. The other tested coating is Clear Gloss Precoat Type II (hereafter abbreviated to Coating B) that is specified to be used on non-porous substrates such as plastics and metals as it contains a small amount of adhesive. For this investigation 100-μm thick polyimide and polyethene substrates were used, which provides a very poor line quality of printed structures when used uncoated. The test substrates were prepared by fixing sheets of A4 size onto a Zehntner vacuum table and the sheets were then coated using a Zehntner ZUA 200.80 universal manual applicator. Each of the coatings was applied at three different thicknesses (5, 30, and 100 μm) on polyimide and four different thicknesses (5, 10, 20, and 50 μm) on polyethene. On each coated substrate a pattern of two test lines, 200 and 500 μm wide with larger contact pads at the ends, were printed, see Fig. 1 for the layout and dimensions. The printer used was a Dimatix 2831 ink jet materials printer together with 10 pL cartridges set to 18 V firing voltage. In order to achieve an optimal line quality it is advantageous to have a high temperature on the printer plate. This leads to a

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8 mm Width 200 μm Width 500 μm

Fig. 1. Layout of the test line pattern that was printed with ANP silver nano-particle ink. TABLE I W ET AND D RY T HICKNESSES OF THE D IFFERENT C OATINGS

Polyimide

Polyimide

Polyethene

Polyethene

Coating A

Coating B

Coating A

Coating B

Applied wet thickness

Dry thickness

Dry thickness

Dry thickness

Dry thickness

5 μm

600 nm

550 nm

600 nm

100 nm

10 μm

-

-

700 nm

350 nm

20 μm

-

-

900 nm

650 nm

30 μm

1300 nm

950 nm

-

-

50 μm

-

-

1300 nm

1800 nm

100 μm

2000 nm

3300 nm

-

-

more rapid evaporation of the ink solvent and therefore a faster setting of the ink particles. The temperature was thus set to 60 °C and the substrate was left on the plate after printing until the ink had visibly dried. In order to evaluate the resistivity the samples were heat treated in a convection oven using steps of 20 min accumulating intervals. The temperatures were 90, 110, 130, 150 °C and in case of polyimide also 200 °C, which is a too high temperature for the polyethene substrates. The resistance was measured in between each step. III. R ESULTS After drying the coatings were measured using atomic force microscopy (AFM), which results are displayed in Table I. The dry contents of the two coatings were established to be 6.2% for Coating A and 6.6% for Coating B by gravimetric analysis. For consistency and in order to avoid any confusion in relation to exactly which coating is being referred to, the wet thickness values will be used when discussing the result if not otherwise stated, although all the coated substrates were thoroughly dried before use. Fourier Transform Infrared Spectroscopy (FT-IR) analysis shows that the main component in both coatings is polyvinylpyrrolidone (PVP), although other contents cannot be ruled out. Mercury intrusion porosity measurements show that the coatings are nonporous. The contact angle for the same solvent as used in the ink, triethylene glycol monoethyl ether, is in the interval of 18–22° for Coating A and 19–23° for Coating B. An interval is given instead of a specific value because the drops were absorbed within 3 s and the coatings starts to dissolve. To be able to state a more precise value the contact angle measurement must be performed during a longer time, which in this case was not possible.

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1 mm Fig. 2.

Measurement areas for calculating line width and raggedness. TABLE II L INE W IDTH AND R AGGEDNESS OF L INES P RINTED ON P OLYIMIDE S UBSTRATES

Uncoated Coating A 5 μm Coating A 30 μm Coating A 100 μm Coating B 5 μm Coating B 30 μm Coating B 100 μm

Line Width Polyimide (μm) 852 490 548 483 471 479 449

Raggedness Polyimide (μm) 13 12 15 25 13 8 9

Fig. 3. Printing quality can be seen to be poor for these 200 and 500 μm wide reference lines printed on polyimide without coating.

1 mm

Fig. 4. Printing quality can be seen to be poor for these 200 and 500 μm wide reference lines printed on polyethene without coating.

TABLE III L INE W IDTH AND R AGGEDNESS OF L INES P RINTED ON P OLYETHENE S UBSTRATES Line Width Polyethene (μm)

Raggedness Polyethene (μm)

Uncoated

856

10 6

Coating A 5 μm

296

Coating A 10 μm

315

7

Coating A 20 μm

343

9

Coating A 50 μm

340

9

Coating B 5 μm

339

11

Coating B 10 μm

358

16

Coating B 20 μm

331

14

Coating B 50 μm

315

5

1 mm

Fig. 5. Printed 200 and 500 μm wide test lines on polyimide with 5-μm thick Coating A.

1 mm

Line quality measurements were performed on 200 μm wide lines. These measurements were made by scanning the printed patterns and analyzing the images in custom image processing software, calculating image quality parameters according to the ISO 13660 standard [21]. The calculations made on these samples (line width and raggedness), were performed on the horizontal parts of the line, between the contact pads. Each line was measured in two separate sections, see Fig. 2, and an average of the two sections was taken as the value in Tables II and III. Raggedness is the geometric distortion of an edge from its ideal position. It is measured as the standard deviation of the residuals from a line fitted to the edge threshold of the line under study, calculated perpendicular to the fitted line. As a reference for line quality measurements the test pattern was also printed on untreated substrates, which showed a very poor line quality, see Figs. 3 and 4. From Tables II and III it is seen that the line definition improvement by the coatings is most distinct for the polyethene substrate. While the line width is similar on both substrate types when uncoated, coating improves (lessens) line width by 36–47% for the polyimide

Fig. 6. Printed 200 and 500 μm wide test lines on polyethene with 5-μm thick Coating A.

substrate and 58–75% for the polyethene substrate, depending on coating type and thickness. Differences in the raggedness characteristic can be observed in Figs. 3–8 for the polyimide versus polyethene substrate. Both for the uncoated and coated samples, the polyimide raggedness shows a higher amplitude, lower frequency appearance, whereas the polyethene lines have a higher frequency and lower amplitude appearance. Microscope pictures of 200- and 500-μm test lines printed on different coating types are displayed in Figs. 3–8. Profilometer measurements were done on all prints with a “Micro Prof” profilometer manufactured by FRT. The printed lines were measured using a step length of 1 μm in x-direction (across the lines) repeating this for 100 scans in the y-direction (along the lines) with 20 μm between the scans for a total measured length of 2 mm. The resolution in


345

10−4 5 μm, Coating A 30 μm, Coating A 100 μm, Coating A

10−5 Resistivity (Ωm)

1 mm

Fig. 7. Printed 200 and 500 μm wide test lines on polyimide with 5-μm thick Coating B.

10−6

10−7

10−8 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Temperature (°C)

1 mm

Fig. 10. Resistivity as a function of sintering temperature for silver ink lines printed on polyimide with 5, 30, and 100-μm thick coatings of Coating A.

10−1

Fig. 8. Printed 200 and 500 μm wide test lines on polyethene with 5-μm thick Coating B.

10 Resistivity (Ωm)

×10−7 16 14 12

z-axis (m)

8

800 700 600 500 400 300 200 100 y-axis (μm)

2000 1800 1600 1400 1200 1000 800 600 400 x-axis (μm) 200 0

10−5 10−6 10−7 60

0

0

z-direction is 10 nm. Because the substrates are transparent they were coated with a thin film of carbon using a sputter to be able to make measurements on the prints. However, the samples are still far from ideal to measure using an optical profilometer. From the data, one average cross-section each for the 200 and 500 μm wide lines was calculated. The 200-μm wide lines have an average cross-section of 245 μm2 and the 500-μm lines an average of 525 μm2 . Fig. 9 displays profilometer scans showing a 500-μm wide line printed on polyimide substrate coated with 100 μm Coating B. The resistivity was calculated based on the measured resistance of the lines for each coating type and thickness. Some assumptions and simplifications regarding the line geometry had to be made for practical reasons, as in reality the ink spreads and forms somewhat irregular lines and, in addition, the thickness will vary over the length. The calculations were based on the average cross sections calculated from the profilometer measurements. This offers a geometry which can be considered to be reasonably correct. The resistivity, ρ, was obtained by inserting the length of the line between contact pads, l, the measured average crosssection, C, and measured resistance, R, in the well-known equation for resistivity C . l

10−4

2

Fig. 9. Profilometer scans showing a 500-μm wide line printed on polyimide substrate coated with 100 μm Coating B.

ρ=R

10−3

6 4

(1)

80

100

120 140 160 Temperature (°C)

180

200

Fig. 11. Resistivity as a function of sintering temperature for silver ink lines printed on polyimide with 5, 30, and 100-μm thick coatings of Coating B.

10−2 5 μm, Coating A 10 μm, Coating A 20 μm, Coating A 50 μm, Coating A

10−3 Resistivity (Ωm)

×10 20 15 10 5 0 −5 1000 900

10

−7

5 μm, Coating B 30 μm, Coating B 100 μm, Coating B

−2

10−4 10−5 10−6 10−7 60

70

80

90 100 110 120 130 Temperature (°C)

140

150

Fig. 12. Resistivity as a function of sintering temperature for silver ink lines printed on polyethene with 5, 10, 20, and 50-μm thick coatings of Coating A.

Plots showing resistivity of the printed lines for different coatings and thicknesses is displayed in Figs. 10–13. When examining the resistivity of the printed lines it can be noted that a common feature for all coating types is that the thinnest coating of 5 μm generally produces the lowest resistivity with the exception of Coating B coated on polyimide. In this case the lowest resistivity obtained for sintering temperatures below

346


100 10−1

5 μm, Coating B 10 μm, Coating B 20 μm, Coating B 50 μm, Coating B

10 Resistivity (Ωm)

−2

10−3 10−4 10−5 10−6 10−7 60

70

80

90 100 110 120 Temperature (°C)

130

140

150

Fig. 13. Resistivity as a function of sintering temperature for silver ink lines printed on polyethene with 5, 10, 20, and 50-μm thick coatings of Coating B.

10−1 −2

10

5 μm Coating B on polyimide 5 μm Coating A on polyimide 5 μm Coating B on polyethylene 5 μm Coating A on polyethylene

Resistivity (Ωm)

10−3 10−4 10−5 10−6 10−7 10−8

60 70

80

90 100 110 120 130 140 150 160 170 180 190 200

Temperature (°C)

Fig. 14. Resistivity as a function of sintering temperature for silver ink lines printed on polyethene and polyimide coated with 5-μm thick layers of Coating A or Coating B.

100 °C is for samples printed on 100 μm coating. Overall, the resistivity difference between the coating thicknesses is particularly large at lower sintering temperatures. On Polyethene substrates, Coating A provides the lowest resistivity at all sintering temperatures. For the polyimide, Coating B provides slightly lower resistivity for 130 °C and 150 °C sintering temperatures, but for all other temperatures Coating A provides the lowest resistivity. The difference between the coating types is particularly large for lower temperatures with a factor of 100 or even greater. Fig. 14 shows a comparison of the resistivity results for 5-μm thick coatings on polyethene and polyimide substrates, which generally give the lowest resistivity values. The lowest measured resistivity values for samples printed on polyethene are 3.5 × 10−7 m for Coating A and 5.7 × 10−7 m for Coating B at 150 °C sintering temperature. For samples printed on polyimide and sintered at 200 °C Coating A gives a resistivity of 8.9 × 10−8 m compared to 1.45 × 10−7 m for Coating B. The lines printed on the coated polyethene sintered at 150 °C have a conductivity of about 4.5% as compared with bulk silver that has a stated resistivity of 1.59×10−8 m. The

Fig. 15. Photo showing printed nano silver ink circuit on polyethene coated with 5-μm Coating A, consisting of a 3 V soft battery (Enfucell) powering two LEDs and controlled by a switch, all mounted with 3M conductive tape.

lines printed on the coated polyimide and sintered at 150 °C have a conductivity of about 7% and on the coated polyimide and sintered at 200 °C about 18%. When these are compared with other substrates, the conductance when sintered at 150 °C fall within the same range as previously reported for ANP nano silver ink printed on photo paper, when sintered at 150 °C [16]. As a demonstration, a circuit pattern was printed on a sheet of polyethene coated with 5-μm Coating A. Sintering was performed in 150 °C after printing. On this pattern two LEDs was mounted powered by a 3 V soft battery manufactured by Enfucell [22]. A momentary switch was also mounted to turn the LEDs on and off. See Fig. 15 for a photo showing the LEDs turned on by applying pressure to the switch by means of a pen. All components were mounted using 3M (9713) conductive tape The line width is 2.5 mm and the total trace length is about 140 mm. The total resistance of the tracks is about 25 . IV. D ISCUSSION An examination of the print quality results shows that the best print quality is achieved on polyethene coated with 5-μm thick Coating A which gives a line width of about 300 μm. When compared to the print pattern of 200 μm, this is an ink spread of 50%. When this is compared to the print pattern it is important to consider that the resolution of prints produced using the Dimatix printer is always dependent on the spreading of the ink drop on the substrate and, as a comparison, it is worth mentioning that the best resolution on highly absorbing photo paper is approximately 240 μm for a 200-μm wide print pattern. The raggedness measurement shows that Coating A provides the most even lines on the polyethene and Coating B on the polyimide substrates. The best coating in terms of conductance was determined to be the Coating A, with a small deviation for coated polyimide sintered at 130 °C and 150 °C. However, it can definitely be stated that this coating provides the best result for lower sintering temperatures. When the thicknesses of the coatings are compared in Table I, the difference between the wet and


Nano particle ink Solvent under ink

Coating

Solvent mixed with coating Nano particle ink Solvent under ink Substrate

Fig. 16. Schematic view showing printed nano-particle ink on coatings of different thickness, where the solvent volume directly beneath the print is larger for the thicker coating.

dry thickness is very large and these do not scale linearly with increasing wet thickness. It is possible that what is happening is that when more coating material is applied it is not being distributed evenly over the surface but is, instead, forming areas with more or less coating and that this is not detected in the AFM measurements because of the rather limited area this instrument can measure. This could then possibly be detected by making a larger number of AFM measurements over the surface, however, the main focus has been to evaluate the applied wet thickness of the coating and its influence on the resulting print quality. It can also be seen that the thinner coating layers result in a lower resistance, the exception being the Coating B on polyimide in which the 5-μm thick coating results in a higher resistance than the 30 μm for a sintering temperatures below 110 °C. The ink consists of silver nano-particles coated in a protective PVP shell that impedes coalescence of the particles dispersed in a solvent. To get a good conduction after printing, the silver particles need to get in a close proximity of each other in order to sinter. As long as solvent and polymers are shielding the particles, this cannot take place. One possible explanation for the high initial resistivity for prints on thick coatings is the retention of the solvent within the coating. Directly after printing the solvent will be adsorbed and partially dissolve the polymer in the coating. For a thin coating the solvent will to a larger extent spread sideways when the volume underneath the ink is saturated. For the thick coating saturation is possibly not obtained, thus a less sideway spreading. This is schematically presented in Fig. 16. The softening of the coating underneath the print also opens for the possibility of partial particle intrusion into the polymer which would shield them to a larger extent compared to their initial polymer shell. This was, however, not possible to establish experimentally due to practical difficulties with sample preparations. After printing, a heating step is necessary to enforce solvent evaporation. For the thin coating the evaporation rate is probably higher thanks to the larger surface area open for the evaporation. For the thick coating where the solvent has penetrated into the coating, the evaporation rate should be less pronounced. The heating step will also provide thermal energy for the polymers and silver particles embedded in the coating (as well as to the particles located above the coating) enabling movements of the polymer chains and the sintering

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of silver. As the temperature is raised the reaction rate is increased. The relatively small resistivity difference that still exists after sintering at higher temperatures, a few times, is quite possibly caused by differences in surface topography. V. C ONCLUSION There are, naturally, more types of nano-particle inks and coatings than those which have been tested in this paper. However, considering that the tested ink is specified for low temperature sintering, which is necessary if low cost polyethene is to be used, it is a good starting point and a good candidate for low cost printed flexible printed electronics. In practice, all nano-particle ink/substrate/coating combinations that are to be used must be evaluated individually before production in order to optimize the combinations and obtain the best performance. The 200 μm wide pattern printed on the coated polyethene substrates resulted in line widths that are about 1.5–2 times the original print pattern as compared to about 4.5 times on the uncoated substrates. Although prints performed on coated polyimide resulted in somewhat wider line widths, both substrates benefit greatly from coating. It can be concluded that applying such PVP-based coatings to polyethene and polyimide will increase the print quality quite substantially, making it possible to print patterns with requirements of smaller line widths and more details than that which is possible without coating. When examining the conductivity it can be seen that the best conductivity is achieved on coated polyimide with about 7% conductance of silver when sintered at 150 °C and 18% when sintered at 200 °C. The difference in conductance between the coatings is very large for lower sintering temperatures and in these cases Coating A is the best choice. R EFERENCES [1] A. Alastalo, T. Mattila, J. Leppäniemi, M. Suhonen, T. Kololuoma, A. Schaller, H. Andersson, A. Manuilskiy, J. Gao, H.-E. Nilsson, A. Rusu, S. Ayöz, I. Stolichnov, S. Siitonen, M. Gulliksson, J. Sidén, T. Lehnert, J. Adam, M. Veith, A. Merkulov, Y. Damaschek, J. Steiger, M. Cederberg, and M. Konecny, “Printable WORM and FRAM memories and their applications,” in Proc. LOPE-C, Frankfurt, Germany, 2010, pp. 1–14. [2] S. M. Bidoki, D. M. Lewis, M. Clark, A. Vakorov, P. A. Millner, and D. McGorman, “Ink-jet fabrication of electronic components,” J. Micromech. Microeng., vol. 17, no. 5, pp. 109–111, Apr. 2007. [3] J.-T. Wu, S. L.-C. Hsu, M.-H. Tsai, and W.-S. Hwang, “Direct inkjet printing of silver nitrate/poly(N-vinyl-2-pyrrolidone) inks to fabricate silver conductive lines,” J. Phys. Chem. C, vol. 114, no. 10, pp. 4659– 4662, Feb. 2010. [4] J. Noh, D. Yeom, C. Lim, H. Cha, J. Han, J. Kim, Y. Park, and V. Subramanian, “Scalability of roll-to-roll gravure-printed electrodes on plastic foils,” IEEE Trans. Electron. Packag. Manuf., vol. 33, no. 4, pp. 275–283, Oct. 2010. [5] S. P. Wu, K. C. Yung, L. H. Xu, and X. H. Ding, “Fabrication of polymer silver conductor using inkjet printing and low temperature sintering process,” IEEE Trans. Electron. Packag. Manuf., vol. 31, no. 4, pp. 291– 296, Oct. 2008. [6] J. Miettinen, K. Kaija, M. Mäntysalo, P. Mansikkamäki, M. Kuchiki, M. Tsubouchi, R. Rönkkä, K. Hashizume, and A. Kamigori, “Molded substrates for inkjet printed modules,” IEEE Trans. Comp. Packag. Technol., vol. 32, no. 2, pp. 293–301, Jun. 2009. [7] S. Joo and D. F. Baldwin, “Advanced package prototyping using nanoparticle silver printed interconnects,” IEEE Trans. Electron. Packag. Manuf., vol. 33, no. 2, pp. 129–134, Apr. 2010.

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Henrik Andersson was born in 1975. He received the M.Sc. degree from Umeå University, Umeå, Sweden, and the Ph.D. degree in electronics from Mid Sweden University, Sundsvall, Sweden, in 2003 and 2008, respectively. He is currently with the Electronics Design Division, Mid Sweden University. His current research interests include printed electronics, printed sensor technology, and semiconductor photon detectors.

Cecilia Lidenmark was born in 1976. She received the Masters degree from Mid Sweden University, Sundsvall, Sweden, in 2002. Her current research interests include chemical aspects of printing and sintering of nanoparticle-inks.

Thomas Öhlund received the M.Sc. degree in engineering physics from the University of Umeå, Umeå, Sweden. He is currently a Ph.D. student with the Digital Printing Center, Mid Sweden University, Sundsvall, Sweden. His current research interests include printed electronics and novel applications, substrate-ink interaction, and sintering.

Jonas Örtegren was born in 1970. He received the Ph.D. degree in polymer technology from the Royal Institute of Technology, Stockholm, Sweden, in 2001. He is currently a Research Leader with the Digital Printing Center, Mid Sweden University, Sundsvall, Sweden. His current research interests include inkjet technology, interfaces, and functional materials.

Anatoliy Manuilskiy was born in 1943. He received the Ph.D. degree in lasers and optics properties from the Department of Radio Physics, Kiev State University, Kiev, Ukraine, in 1971. He is currently a Senior Researcher with the Electronics Design Division, Mid Sweden University, Sundsvall, Sweden. His current research interests include development of laser systems, laser optics, and printed nano-structures.

Sven Forsberg was born in 1956. He received the Masters degree in chemistry, and the Lic.Eng. degree in physical chemistry both from the Royal Institute of Technology, Stockholm, Sweden, in 1982 and 1990, respectively. He was with Surface Chemistry Institute, Stockholm, for seven years. He has ten years of experience from industrial research in the paper industry. He is currently with Mid Sweden University, Sundsvall, Sweden. His current research interests include novel applications of paper.

Hans-Erik Nilsson received the Ph.D. degree in solid state electronics from the Royal Institute of Technology, Stockholm, Sweden, in 1997. He became a Senior Researcher with Mid Sweden University, Sundsvall, Sweden, in 1997, focusing on modeling of advanced semiconductor devices. In 2002, he became a Full Professor in electronics. His current research interests include quantum transport in electron devices, radiation imaging detectors, radio-frequency electron devices, printed radio-frequency identification antennas, printed sensor technology, and wireless sensor networks.