High Performance Silver Inks for Cost-Efficient Manufacturing
- khashayar Ghaffarzadeh
- Oct 6
- 8 min read
Author: Thibaut Soulestin, PhD; Technology Manager Printed Electronics; Henkel Adhesive Technologies; thibaut.soulestin@henkel.com
Henkel Adhesive Technologies holds leading market positions worldwide in the industrial and consumer business. As a global leader in the adhesives, sealants, and functional coatings markets, Henkel has developed a large material portfolio of LOCTITE® conductive inks and coatings. The LOCTITE® Printed Electronics portfolio offers more than 100 different material solutions. Among those, Henkel silver inks are known to be exceptionally reliable, easy to use, and require only simple handling. This portfolio refers to products with proven superior performance in terms of conductivity and printability.
This article focuses on a handful of silver inks to provide insights into the selection of the most cost-effective inks for various applications, such as membrane switches, capacitive touch sensors, heaters, and antennas. It introduces the latest Henkel developments in very high conductive inks with LOCTITE® ECI 1017 and cost-efficient silver-plated copper inks with the LOCTITE® ECI 4000 series. Efficient manufacturing of hybrid electronics is also enabled by proven compatibility with a range of electrically conductive adhesives or low-temperature solder pastes.
1. Silver Inks Overview
1.1 Main properties
With the large range of silver inks available for PET substrates - selecting the most cost-efficient is not easy as you need to balance the material cost in €/kg, electrical conductivity, coverage and processability.
Ink cost is strongly driven by the silver content, the quality of the silver particles, and performances of the polymer binder.
1.1.1 Sheet Resistance
Electrical conductivity is expressed as sheet resistance. ASTM F1896 describes the test method.
From the sheet resistance value, it is easy to calculate the expected track resistance:
By using a low sheet resistance ink, you can reduce the thickness of the ink by printing with a finer screen or print narrower tracks.
1.1.2 Theoretical Coverage
Theoretical coverage is the surface you can print in m², at a target dry thickness (often normalized to 10 µm), with 1 kg of liquid ink. The higher the coverage, the higher the number of prints you can make with 1 kg of ink.
1.1.3 Curing Process
Ink curing can refer to different processes related to ink solidification.
Solvent evaporation: Most of the silver inks for PET substrates become solid by simple solvent evaporation. The evaporation speed is driven by the temperature and air flow.
Solvent evaporation + cross-linking: The chemical cross-linking reaction can be activated by heat or UV.
Solvent evaporation + sintering: Heat sintering can be performed in a standard oven or may require high energy radiation sources like near-infrared, xenon, or photonic.
1.2 Highlighted LOCTITE® Silver Inks
Among more than 30 different silver inks in LOCTITE® portfolio, 4 are particularly relevant for screen-printing on PET and covers are large range of applications (Table 1). Table 1. Overview of high-runners Henkel LOCTITE® silver inks.
LOCTITE® EDAG PF-410 is a highly reliable silver ink qualified in numerous applications across industries. The formulation brings long-open screen time. It has good adhesion on a large range of substrates, including metals, glass or ceramics. This ink is compatible with a wide range of carbon inks, dielectric inks, but also numerous electrically conductive adhesives or low-temperature solder pastes. Processing up to 180°C for a few minutes will not trigger accelerated aging. It is the go-to ink when low sheet resistance is not mandatory.
LOCTITE® ECI 1001 is suitable for non-demanding applications where low track resistance is not required. Excellent choice for membrane switches or capacitive touch sensors. This ink has the lowest price in the Henkel silver ink range thanks to the low silver content. The cost-efficiency is even improved with the high coverage of 17 m²/kg at 10µm dry. The cost performance still comes along with good reliability in 85°C/85%RH and excellent flexibility.
LOCTITE® ECI 1010 is Henkel state-of-the-art silver inks. With one of the lowest sheet resistances (0,006 Ohm/sq/25µm) for a flexible ink on the market, this ink is the perfect balance between electrical conductivity and cost. It is very flexible and shows minimal resistance increase under double-crease test. Thanks to the small silver flake size, this ink can be printed with fine screens for low thickness and narrow tracks, improving further the cost-efficient without compromising the technical performances. Next to HMI applications, LOCTITE® ECI 1010 is suitable for antenna or heaters up to 100°C.
LOCTITE® ECI 1011 is the lowest sheet resistance ink in the portfolio with 0,003 Ohm/sq/25µm. Such a low sheet resistance is enabled by sub-micron particles that sinter at 150°C in traditional conveyor ovens. In comparison to nano-particles inks or molecular inks, the use of sub-micron inks provides higher dry thickness and higher production throughput. The small particle size gives low surface roughness and sharp edges. Combined with the excellent electrical conductivity, LOCTITE® ECI 1011 is particularly suitable for antenna applications.
1.3 Reliability
All LOCTITE® silver inks undergo accelerated ageing for at least 1000 hrs in a climate chamber at 85°C and 85% of relative humidity before commercialization in Henkel R&D laboratories. The bare silver ink on PET is tested. Compatibility by overprinting carbon and dielectric inks is also evaluated.
Figure 1 displays the sheet resistance change of the 4 highlighted silver inks after 1000 hrs in 85°C/85%RH condition. Due to the low silver content, ECI 1001 shows a slight increase of sheet resistance, not detrimental for the targeted applications. EDAG PF-410 sheet resistance decreases until stabilization. This decrease can be explained by the improved stacking of the large silver flakes. Both ECI 1010 and ECI 1011 demonstrate excellent sheet resistance stability.
Dry heat storage tests at 100°C or above, for the bare silver inks or when overprinted with carbon or dielectric inks, are available upon request to your Henkel contact.
2 Towards More Cost-Effective Inks
2.1 Very Low Track Resistance - LOCITITE® ECI 1017
Launched in 2025, LOCITITE® ECI 1017 completes the range of very high conductivity sintered silver inks. Similarly to LOCTITE® ECI 1011, it sinters in traditional conveyor ovens at 140-150°C. With a sheet resistance of 2.6 mOhm/sq/25µm, the main difference with ECI 1011 lies in the dry films thickness. ECI 1017 prints 2x thicker than ECI 1011.
The higher dry ink thickness and the very low sheet resistance gives extremely conductive silver tracks. Particularly suitable for sensing or antenna applications. Figure 3 shows the influence of temperature and time, in a ventilated box oven, for 3 silvers inks: ECI 1010, ECI 1011, and ECI 1017. ECI 1010 dries in 10 min at 120°C while 5 min is only required at 150°C. Shorter times are observed with conveyor ovens. ECI 1011 needs 150°C for sintering as observed by the resistance drop between thermal treatments for 15 min at 120°C or 150°C. ECI 1017 dries and sinters faster than ECI 1011. Partial sintering already occurs at 120°C but it is recommended to process at 140-150°C to achieve the lowest track resistance.
As displayed in Figure 3, there is a 3x resistance difference between ECI 1010 and ECI 1017 when printed with the same screen. ECI 1010 has a remarkable sheet resistance of 0,006 Ohm/sq/25µm combined with an excellent flexibility. The resistance increase after a double crease test is below 10%. All sintered silver inks can withstand small bending radius of a least 4 mm but will crack under double-crease test.
2.2 Silver-plated copper – LOCTITE® 4000 series
Silver price volatility is a constant challenge for the Printed Electronics industry. After record prices in 2011, above 40 USD/oz, in 2025 prices are again at a similar level. Pure copper inks are expected to offer more stable prices and overall lower cost. Different technologies have been developed to prevent copper oxidation. They all require additional processing like 2K ink blending, inert atmosphere sintering, hot pressing, high-power radiation. In addition, sintering reduces the flexibility of the printed copper tracks. Those drawbacks slowed down the adoption rate of those inks.
Silver-plated copper inks appear as an alternative solution for more cost-effective conductive inks. The silver shell protects the copper from oxidation in high-humidity environments. Recent developments in flake manufacturing and ink formulation are now leading to flexible conductive inks with good electrical conductivity, and high reliability in high-humidity environment, suitable for membrane switches or capacitive touch sensor applications.
3 Hybrid Electronics
3.1 Electrically Conductive Adhesives
Henkel is the premier materials supplier for the electronics assembly and semiconductor packaging industries. The advanced formulations include a range of products that facilitate electrical interconnect, provide structural integrity, offer critical protection, and transfer heat for reliable performance.
Attaching components, such as LEDs, on printed silver lines is enabling Hybrid Electronics and combines the “best of the two worlds”. Compatibility between silver inks and electrically conductive adhesives (ECA) were tested by accelerated aging for 1000 hrs at 85°C and 85% relative humidity. The die shear stress (DSS) and the single joint contact resistance (SJCR) were measured. EDAF PF-410, ECI 1010, and ECI 1011 are compatible with Ablestik CE 3104WXL, Ablestik 3103WLV, Ablestik 2030SC, Ablestik QMI516IE, and Ablestik 57C 2K. After 1000 hrs at 85°C/85%RH, the die shear stress is above 0,5 kg and single joint contact resistance below 50 mOhm. The main adhesion failure is between the substrate and the silver ink. For even higher long-time reliability, it is recommended to use noble component finish like AgPd or Au instead of Sn.
A straightforward way to evaluate the compatibility between an ECA and a silver ink is by looking from the bottom side of the print. Any discoloration of the silver under the ECAs indicates a risk of incompatibility (Figure 5)
3.2 Low Temperature Soldering
In addition to ECAs, it is possible to bond components using Tin-Bismuth, Sn42Bi58, low-temperature solder paste. To allow the formation of a good intermetallic compound and keep adhesion on the substrate, a thick layer of silver ink is needed. A second print can be done on the contact pads. LOCTITE® EDAG PF-410 is recommended for its compatibility with low temperature soldering and can also be used as an additional layer on the contact pads when other silver inks are printed.
4. Conclusion
Built on decades of expertise in Printed Electronics, Henkel ink portfolio keeps evolving to offer more sustainable, more conductive, more reliable, and more cost-efficient solutions to the industry. This article highlighted the main silver inks for screen-printing onto PET substrates.
All new developments aim at improving the end product sustainability by (i) reducing the ink carbon footprint, (ii) improving the sustainability of the manufacturing, and (iii) improving the end product life cycle. Supporting claim (i), product carbon footprint of all Henkel inks and calculation methodology are available for Henkel customers.
The silver ink range is much wider with inks for a variety of substrates such as PC for In-Mold-Electronics, TPU for medical and wearables, FR-4 for printed circuit boards. It is also worth mentioning the available wide variety for a large range of printing processes such as 3D printing by pad-printing or jetting; or high-speed printing with rotogravure and flexographic printing.
What to expect in Berlin?
Comments