How to use conductive adhesives/silver pastes

Conductive adhesives and silver pastes are attracting increasing attention, but incorrect handling can prevent them from delivering their intended performance.
This page explains how to use conductive adhesives, using thermosetting and solvent-drying types as examples. It covers the basic steps of thawing, cleaning, dispensing, and curing or drying, together with important handling points.

What Is a Conductive Adhesive / Silver Paste?

A conductive adhesive is an adhesive that conducts electricity. Many products contain silver as the conductive filler and are therefore also called silver paste or silver-filled conductive adhesive.
Because conductive adhesives can bond certain metals, resins, and other materials that may be difficult to solder, they are used in a wide range of applications.

As the use of heat-sensitive films and resins has increased, conductive adhesives have expanded as an alternative conductive joining method where soldering temperatures may be unsuitable.
This page uses KAKEN TECH's TK PASTE Series as an example to explain the basic handling procedure.

TK PASTE Product Information

Basic Steps for Using Conductive Adhesives

How to Use Thermosetting Conductive Adhesives

	[Thawing] Thaw the frozen conductive adhesive while keeping the container tightly sealed. Leave it at room temperature for at least 30 minutes. Before opening, wipe away any condensation from the outside of the container. Thaw at room temperature. Do not force-thaw the product using hot water, a hot plate, oven, hair dryer, or other direct heating method. Prevent condensation from entering the adhesive. Opening the cap while the container is still cold can allow moisture to enter and may adversely affect the material.
	[Cleaning] Clean the bonding area with a suitable solvent such as alcohol or acetone, where compatible with the substrate. Flux residue, oil, and other contamination can reduce electrical and bonding performance. Allow the cleaning solvent to dry completely before applying the adhesive.
	[Dispensing] Apply an appropriate amount of adhesive. A dispenser can help control deposit volume and placement accurately. Select a needle with an internal diameter appropriate for the adhesive. A needle that is too small may clog. After dispensing, proceed to curing promptly. Excessive delay before curing can affect final performance. Temperature and humidity in the work environment can affect handling and performance. For the products described here, a working temperature of 25℃ or below is recommended.
	[Curing] Thermosetting conductive adhesives develop their intended properties through heat curing. Use a temperature-controlled oven and cure according to the recommended conditions for each product. Use an oven capable of maintaining a stable and uniform temperature. Hot plates and hair dryers may heat the workpiece unevenly. Curing behavior varies with temperature, time, applied amount, workpiece thermal mass, and oven loading. Validate the curing profile using the actual equipment, substrate, bond geometry, and production conditions.

How to Use Solvent-Drying Conductive Pastes

	[Thawing] Thaw the frozen conductive paste while keeping the container tightly sealed. Leave it at room temperature for at least 30 minutes and wipe away external condensation before opening. Do not force-thaw the product using direct heating, and prevent condensation from entering the paste.
	[Cleaning] Clean the application area with a suitable solvent such as alcohol or acetone, where compatible with the substrate. Allow the cleaning solvent to dry completely before applying the paste.
	[Dispensing] Apply an appropriate amount of paste. Select a needle with an internal diameter appropriate for the paste. For the products described here, a working temperature of 25℃ or below is recommended.
	[Drying] Solvent-drying conductive pastes develop their intended properties as the solvent evaporates. Dry according to the recommended conditions. Drying behavior varies with temperature, time, applied amount, ventilation, workpiece geometry, and oven loading. Validate the drying conditions using the actual equipment and materials.

Key Points for Stable Conductive Adhesive Performance

Even when the same conductive adhesive is used, electrical conductivity and adhesion can vary depending on storage conditions, thawing method, the surface condition of the adherend, the applied amount, and curing or drying conditions. To achieve stable performance, it is important to control not only the adhesive itself but also the entire handling and application process.

1. Store Under the Specified Conditions

Conductive adhesives should be stored at the temperature specified for each product to minimize reactions during storage, solvent loss, and changes in material condition. Some TK PASTE products require frozen storage. Check the storage requirements before use and maintain the specified temperature.

2. Thaw at Room Temperature with the Container Sealed

Conductive adhesives stored frozen should be thawed at room temperature while the container remains tightly sealed. Opening a cold container may allow moisture from the air to condense and enter the adhesive. Allow the container to warm sufficiently, wipe off any condensation from the outside, and then open it.
Avoid forced thawing using hot water, a hot plate, oven, hair dryer, or other direct heating method.

3. Remove Contamination from the Bonding Surface

Oil, flux residue, and other contamination remaining on the adherend can affect electrical conductivity and bond strength. Before applying the adhesive, clean the bonding surface using a cleaning agent compatible with the adherend and allow it to dry completely.

4. Keep the Applied Amount Consistent

Performance after bonding can vary with the applied amount and bond-line condition. In mass production, a dispenser can help keep the dispensing position and amount consistent. Select a needle diameter appropriate for the adhesive viscosity and conductive particle size.

5. Control Curing and Drying Conditions Properly

For thermosetting types, consider not only the oven set temperature but also whether the adhesive itself reaches the required temperature. Heating behavior varies with the applied amount, the material and size of the adherend, and oven loading.
For solvent-drying types, solvent evaporation also varies with temperature, time, and applied amount. Use the published conditions as a reference, then evaluate the adhesive with the actual equipment, materials, and application amount.

6. Evaluate Under Actual Application Conditions Before Production

Conductive adhesive performance is affected by adherend material, surface condition, application method, bonding area, and curing conditions. Before mass production, evaluate electrical conductivity, bond strength, curing or drying condition, and other required properties using the actual materials and equipment.

Frequently Asked Questions About Conductive Adhesives

	Product Information Conductive Adhesive FAQs Answers frequently asked questions about the TK PASTE Series, including how to open syringes, whether a dispenser is required, storage and handling, and how to obtain product-property data.

Related Articles & Products for Conductive Adhesives

	Technical Solutions Conductive Adhesives Using TK Silver Powder Introduces low-silver, low-specific-gravity conductive adhesives using specially shaped TK Silver Powder.
	Technical Solutions What Is a Conductive Adhesive? Explains how conductive adhesives conduct electricity, their main types, and their differences from solder and conventional adhesives.
	Product Information TK PASTE Conductive Adhesives Conductive adhesives for bonding heat-sensitive materials and other substrates that can be difficult to solder.
	Product Information TK PASTE CR-5200 Conductive Adhesive A conductive adhesive developed for heat-sensitive materials and circuits such as resins and films.