A Guide to Glue for Electronic Devices: A Must-Know for Hardware Engineers

In the manufacturing and assembly process of electronic devices, various glues are often used to ensure the stability and protection of components. Here are a few commonly used glues and their applications:

1. 502 glue (instant glue):

• Chemical Composition: Cyanoacrylate.
• Properties: Extremely fast curing, initial strength can be reached in seconds to minutes.
• Applications: Suitable for rapid bonding of various materials (e.g., plastics, metals, rubber, and ceramics), often used for temporary fixation and small area bonding, but not for applications that require high durability and heat resistance.

  

703 glue (silicone):

• Chemical Composition: Silicone.
• Characteristics: high temperature resistance, moisture resistance, aging resistance, good electrical insulation properties, elasticity after curing.
• Application: Widely used for sealing, insulation and waterproof treatment, suitable for occasions that require elasticity and environmental protection, such as the protection of circuit boards and the sealing of cables.

  

Underfill(底部填充胶):

• Chemical composition: epoxy or other thermosetting material.
• Characteristics: Cured after heating, with high strength and low coefficient of expansion, able to provide stable performance at high temperatures and mechanical stress.
• Application: It is mainly used to fill the gap between the chip and the substrate to enhance the mechanical strength and thermal cycling reliability of the solder joint, and is commonly used in advanced packaging technologies such as BGA (Ball Grid Array) and CSP (Chip Scale Packaging).

  

  

704 Glue (Silicone):

• Chemical Composition: Silicone.
• Characteristics: Similar to 703 glue, but with better high temperature resistance, moisture resistance, aging resistance, and good electrical insulation properties.
• Application: It is widely used for sealing, insulation and waterproof treatment of electronic components, and is suitable for occasions that require higher temperature resistance, such as circuit board protection in high-temperature working environments.

  

• High temperature resistance: 704 rubber has higher high temperature resistance than 703 glue and can maintain its properties at higher temperatures.
• Application Scenario: Due to the higher high temperature resistance of 704 adhesive, it is more suitable for circuit board protection and other applications that require higher temperature resistance in high-temperature working environments, while 703 adhesive is suitable for sealing and insulation in general environments.

AB glue (two-component glue):

• Chemical composition: epoxy resin and curing agent, divided into A part and B part, need to be mixed in proportion when used.
• Characteristics: After curing, it has the characteristics of high strength, corrosion resistance, heat resistance, water resistance, etc., and the curing time is longer, but the strength and stability are high.
• Application: Widely used to bond materials that require high strength and durability, such as metals, ceramics, glass, plastics, etc., and are commonly used for structural bonding and repair.

  

Red glue (SMD glue):

• Chemical Composition: Epoxy resin.
• Characteristics: fast curing, high strength, good heat resistance.
• Applications: Widely used in surface mount technology (SMT), especially to secure components prior to reflow soldering.

  

Electrically conductive adhesives:

• Chemical composition: Epoxy resin or silicone containing conductive fillers such as silver powder.
• Characteristics: It can conduct electricity after curing, and has good electrical conductivity and mechanical properties.
• Application: Used to connect electronic components, replace traditional soldering, and are suitable for bonding that requires electrical conductivity, such as flexible circuit boards and electromagnetic shielding.

UV Glue:

• Chemical Composition: Light-curable resin.
• Characteristics: Ultraviolet light source is required for curing, fast curing speed and high transparency.
• Applications: Used in applications where fast curing and high transparency are required, such as bonding and protecting optical components.

  

Hot Melt Adhesives:

• Chemical Composition: Thermoplastic resin.
• Characteristics: It has good fluidity after heating and melting, and cures quickly after cooling, and has good adhesive strength.
• Application: It is widely used in the fixing of wires and cables, the packaging and protection of electronic components.

  

Epoxy adhesive:

• Chemical Composition: Epoxy resin.
• Characteristics: High strength, chemical resistance and good insulation properties after curing.
• Applications: For encapsulation, potting and protection of electronic components, especially where high strength and durability are required.

  

Silicone glue:

• Chemical Composition: Silicone.
• Characteristics: good flexibility, high and low temperature resistance, chemical corrosion resistance, good electrical insulation properties.
• Application: It is used to seal and protect electronic components, circuit boards, etc., and is suitable for application scenarios with high environmental requirements.

  

Polyurethane glue:

• Characteristics: good flexibility, excellent waterproof and sealing performance, wear resistance, chemical resistance.
• Applications: Suitable for applications that require high strength and waterproof performance, such as sealing, potting and encapsulation of electronic components.

  

Acrylic glue:

• Characteristics: Good adhesion and waterproof performance, UV resistance and aging.
• Application: For the protection of outdoor electronic devices and electronic components exposed to the environment.

  

Butyl glue:

• Characteristics: Excellent waterproof performance and sealing performance, good flexibility and strong weather resistance.
• Application: It is often used for the sealing of cables and pipe interfaces, and the waterproof treatment of electronic equipment.

The diversity of these glues allows hardware engineers to choose the most suitable glue for different needs, improving the reliability and performance of the product.

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