Hot melt glue for consumer electronics assembling:

Today, with modern technology, a lot of new hot melt glues are available and usually used to assemble smartphones, tablets, wearable electronic devices, wireless speakers and electrical appliances. This is a real evidence for us to see the importance of hot melt glues in the electronics industry in general and consumer electronics industry in particular.

Hot melt glue is a solvent-free adhesive and in solid-type at temperatures below 80°C. Above that temperature, they are low viscosity liquids and will be quickly established when cooling. While some liquid adhesives can take about 8 - 24 hours to dry and stick, hot melt adhesives usually have a drying time of about one to five minutes. This helps to reduce assembly time and costs during production.

Advantages of using HOT MELT GLUE to assemble consumer electronics:

1. Hot melt adhesives help form fast links that help increase productivity.

2. There are many methods allow engineers to be flexible when conducting assembly.

3. There are many types of hot melt glues that help to connect all porous surfaces.

4. Hot melt adhesive has a good gap filling ability that allows larger tolerances in component design.

5. Hot melt glue has excellent moisture resistance.

6. They are durable and do not require refrigeration or other environmental controls.

Some hot melt adhesives are available on the market today: hot melt glue stick, polyurethane hot melt adhesive (PUR hot melt glue) and polyolefin hot melt adhesive (polyolefin hot melt glue) are increasingly replacing adhesive tape and other adhesives for assembling screen, shell and battery.

Hot melt glue sticks

Hot melt glue stick has high moisture resistance and effectively bonds flexible materials with metals.

Working temperature of the glue ranges from 120 to 140°C. The glue is sprayed onto the surfaces by automatic or manual spraying devices. The nozzle head can be as small as 0.5mm.

After hot melt glue stick is sprayed on the surface of the material, they will work immediately.

After treatment, the glue also provides long-term protection against chemicals, moisture, dust and other environmental pollutants. In addition, due to the natural flexibility of the glue, it helps to enhance device's shock resistance.

The glue has a slight odor and less than 15 grams per liter of volatile organic compounds. They do not contain di-isocyanates that are sensitive to the skin.

PUR hot melt glues

Single component PUR hot melt adhesive has low halogen concentration to link the structure of portable electronic devices. PUR hot melt glue is very suitable for bonding metals, ink and plastic coated glass, anti-shock and impact-resistant items. Over time, it reacts with moisture so that cross-linking with polymer creates excellent durability.

The working temperature range of PUR hot melt glue is about 90 to 110°C. The glue has a relatively long opening time: At 25°C, for spraying where the diameter is 1 mm, the opening time of the glue is 4 minutes.

PUR glue is widely used in electronics assembly for applications such as connecting screen to phone covers.

Previously, double-sided tape was used for this application. However, it is not strong enough to link the thin border screen design from 0.4 to 0.5 mm as today. The assembly fail and the low withstand heat ability are the errors encountered during the inspection and evaluation of product quality.

In addition, electronics manufacturers are trying to make their mobile devices more waterproof. The really thin tape does not have the ability to prevent water penetration. However, melting glue can provide the ability to fill the void and help waterproof for assembly.

Flexible lithium-ion battery is another application for PUR hot melt glue. Previously, the edges of these batteries would be folded and sealed with single-sided tape. Now, battery manufacturers are using PUR hot melt glue to replace it.

In addition, double-sided tape is also replaced by PUR hot melt glue to keep the battery in place inside the mobile device. With slot coating technology, PUR glue can cover a strip of 8 mm wide and about 100 microns thick. The glue can be sprayed in any angle by robots or automated systems to save time, labor, and  increase productivity.

Other applications for PUR hot melt glue include compact camera modules, wireless speakers, headphones and wearable electronics devices.