Will There Ever Be a Role for Nanosilver?

Published: February 07, 2013 Category: Advanced Materials

Nanosilver inks and pastes have been under development for some time. One of the major claims of printable nanosilver has been that, although it is certainly more costly on a per-weight-unit basis, less of the material is needed to achieve the same level of conductivity compared to conventional materials.  In addition, nanosilver's smaller particle size enables lower-temperature sintering and inherently higher resolution in printed patterns.

But these claims have not resulted in successful commercialization of printed nanosilver on a large scale:

• In reality, the high price of nanosilver has heretofore largely precluded its use in many traditional electronics applications. Even in today's market, in which silver's price is rising faster than the price of nanosilver materials, the balance has not (yet?) appreciably shifted in favor of nanosilver.

• Furthermore, even if high silver prices do eventually shift the economics in favor of nanosilver, this shift will be converted into opportunity only by those nanosilver suppliers who can tangibly demonstrate both technical and economic benefits for their customers. In other words, customers will look for materials that provide high performance, comparable or lower cost-in-use than conventional silver products, and easy-to-handle options.

Demonstration of the benefits should come the easiest in emerging electronics applications, where new printed electronics technologies are on an upswing of their own, and conventional silver is not already entrenched, such as in printed electronics applications that are emerging as part of the ubiquitous computing and/or Internet-of-Things phenomenon.  These new applications may also be more able to support nanosilver's higher price, at least for a few more years, than traditional electronics applications.

Of course, the downside to this approach is that many of these novel printed electronics applications are not yet on the market in a significant way. Thus, a complementary strategy for the nanosilver ink and paste business is to stress niche products that actually exist, and in which printed nanosilver has obvious and immediate competitive advantages-like miniaturized PCBs, certain types of capacitors, and printed sensors.

Nanosilver inks: Most of the nanosilver ink products on the market have been targeted towards inkjet processing, which is typically a good fit for high-resolution printing, if not for high-throughput (although some advancements in the speed of inkjet printing have occurred over the last couple of years).

To meet the needs of high-throughput processes, nanosilver inks designed for flexographic, gravure, offset, and other high-volume printing methods have also been of interest, although they generally lag behind inkjet inks in development and commercialization. Note that low-viscosity printing-also a feature of inkjet, flexographic, and gravure printing-is tailor-made for nanosilver. 

What about nanosilver pastes?

Although most applications for screen-printed silver are still defined by conventional silver pastes, there have also been advancements in nanosilver pastes.

For example, Advanced Nanotech (Korea) and Harima (Japan) both offer nanosilver pastes for higher-resolution screen-printing as a way to help manufacturers transition to nanosilver materials without wholesale changes in the printing method. These nanosilver products will come into play more frequently where finer patterning and better uniformity are needed. However, this commercialization effort has been going on for several years now, with very little to show for it.

But how far can nanosilver go?

While any successes in the inkjet sector will be associated with nanosilver, such a relationship may not be the case for the other printing methods. We note that conventional silver materials are also being successfully developed into inks compatible with flexographic, gravure, and other printing methods, which means that the use of nanosilver may not be required after all. In fact, NanoMarkets' belief is that end users will remain with the tried and tested materials unless they can be persuaded to move to more sophisticated materials.

Furthermore, today the advantages of nanosilver inks over conventional silver inks and pastes come at the cost of greater difficulty in preparing them and the nanosilver particles they contain.  This greater process difficulty carries through to a higher cost-per-gram of silver contained in the inks. 

In other words, often, the additional cost of going "nano" negates the savings of using less material, and the cost of nanosilver inks per square meter of printed area ends up being higher than for conventional silver inks and pastes.  For firms that are already looking for ways to lower costs in a world of high silver prices, this equation does not sit particularly well.

Nevertheless, we continue to hold the view that the development of silver nanoparticle inks may be an important long-term formulation trend in silver inks. The advantages obtainable with nanosilver inks could, we believe, still pay off in certain circumstances.  In particular, we see four possible ways that nanosilver could improve its prospects:

• Obviously, reductions in the cost of nanosilver inks would go a long way toward making them more attractive.  The benefits of using smaller quantities of silver are obvious, and while nanosilver may be expensive now, it is still an immature material.  It may take a few years for the cost of those smaller quantities of nanosilver inks and pastes to fall below that of the larger quantities of conventional silver inks and pastes, but it is reasonable to believe that it will happen in the long run.

• Printing precision is increasingly important as electronics across many applications are being miniaturized, i.e., as more and more electronic functionality is being crammed into ever-smaller units. Nanosilver ink formulations can produce finer, more reliable line widths than their conventional silver counterparts, even if multiple layers are required to build suitable aspect ratios. 

• When fragile substrates (very thin wafers used in PV applications, for example) or roll-to-roll (R2R) printing are used, an argument might be made in some cases that one or more of these alternative printing methods is the way to go. Inkjet, for example, makes sense when non-contact printing is desired.

• Low-temperature processing could be an enabler for some very low-cost, flexible electronics technologies fabricated on flexible substrates.  Here, the small size of the nanoparticles can facilitate lower-temperature curing of the printed silver, since sintering temperature in metallic pastes and inks is a function of particle size. This advantage potentially produces additional important opportunities for nanosilver as an alternative to conventional silver pastes.