Five Questions Before Choosing an Electronic Adhesive

Electronic adhesives are grouped in this portfolio by function: bonding and sealing, conformal coating, potting protection, electromagnetic shielding and conductive connection. Each function answers a different question, so the first step is to name the function before comparing grades.

1. Is the job bonding, coating or filling?

Bonding and sealing products are described as featuring excellent adhesion and resistance to high and low temperatures, usable long term from -60 to 200°C, and widely used for bonding and sealing of electronic components and electronic and electrical equipment.

Conformal coating is a surface treatment. The one-component silicone resin product CGFT-8181 is described as curing at room temperature with a tack-free time of ten minutes or less, as a phenyl silicone resin based product with high transparency and strength, and as meeting the verification requirements of the electrical insulating compounds standard for coated printed board assemblies.

2. What does the cure schedule allow?

Cure chemistry determines whether the product can be used on a heat-sensitive assembly. Room-temperature moisture curing is described for GD-443T at 25°C over 24 hours as a one-component condensation-type alkoxy product: neutral, solvent-free and low odour.

One-component heat curing is also available and is described as offering high efficiency and excellent universal adhesion.

One-component room-temperature curing silicone adhesives such as GD-883D and GD-852L for component fixing.
One-component room-temperature curing grades GDA-8152 and GD-950 for bonding and sealing of metal, glass and plastic parts.
One-component thermoset and neutral non-corrosive grades GDA-6090 and GD-406 for electronic encapsulation.

3. Does the assembly move?

Rigid adhesives transfer stress into the joint; elastomeric silicone adhesives absorb it. Silicone elastomer products are used where differential thermal expansion between substrate materials would otherwise crack a joint or a solder fillet.

Low cyclic siloxane content grades such as GD-8140B and self-levelling grades such as GD-408 are stated for bonding and coating in office automation equipment and sensors.

4. What is the environment?

The service temperature range, moisture, salt spray and fungus resistance all belong in the same question. The conformal coating products are described as having excellent moisture, fungus and salt-spray resistance and are mainly used for conformal coating of PCB boards in precision electronics.

For photovoltaic and outdoor equipment the stated grades include GD-769 and GD-883, described for bonding and sealing in the photovoltaic industry.

5. Is the connection electrical?

Once the joint has to conduct, the material class changes. Electromagnetic shielding is described as preventing electronic equipment from interfering with other equipment while also protecting it from interference by others, and shielding materials are stated for electronic communications, mobile phones, computers, general electronic devices, network equipment and medical equipment.

Conductive grades include GD-500, described as silver conductive with a volume resistivity below 0.005 Ω·cm, and GD-507, described as nickel-carbon conductive with a volume resistivity below 1 Ω·cm.