What is the difference between solid crystal solder paste and red glue?

Solid crystal solder paste and red glue are two common materials in the field of electronic packaging, and they have significant differences in composition, function, process, performance and application. The following are their main differences:

I. the composition and function

Solid crystal solder paste:

Composition: mainly composed of metal alloy tin powder (such as tin-lead alloy, tin-silver-copper alloy, etc.) and flux.

Function: melted at high temperatures to form metal solder joints, to achieve electrical connection and mechanical fixation between the chip and the substrate, as well as thermal conduction.

Red glue:

Composition: usually composed of epoxy resin, filler (such as silica) and curing agent.

Function: after curing to form a bonding layer with a certain mechanical strength, mainly used for mechanical fixation between the chip and the substrate, does not provide electrical connection.

II. the process and temperature

Solid crystal solder paste:

Process: usually reflow soldering process, that is, the paste is printed on the substrate, and then fix the chip, and finally through the reflow furnace for high temperature heating, so that the paste melts and forms a solder joint, complete the chip and the substrate of the welding.

Temperature: The reflow temperature is generally between 200-260°C, depending on the composition of the solder paste and the material of the substrate.

Red glue:

Process: It can be cured by heat curing or UV curing.Heat curing usually uses an oven to heat curing at a lower temperature (e.g. 120-150°C); UV curing uses UV lamps for irradiation curing.

Temperature: the curing temperature is relatively low, less damage to heat-sensitive components.

III. performance and reliability

Solid crystal solder paste:

Performance: excellent electrical conductivity, thermal conductivity and mechanical strength, to ensure electrical connection and mechanical stability between the chip and the substrate.

Reliability: solder joints after high temperature reflow to form intermetallic compounds, with high shear strength and thermal fatigue resistance, suitable for long-term reliable application scenarios.

Red glue:

Performance: after curing to form a bonding layer with a certain degree of elasticity, can absorb stress and protect the chip and substrate from damage.However, red adhesive is not conductive and cannot provide an electrical connection.

Reliability: The relatively low bond strength and temperature resistance of red adhesives may not meet the needs of certain high-reliability applications.In addition, red adhesive may soften or degrade at high temperatures, affecting its bonding performance.

IV. Application Scenarios

Solid crystal solder paste:

Application Scenario: Widely used in the field of flip chip packaging, such as QFN (Quad Flat No-lead), BGA (Ball Grid Array), LED and other packaging forms.In these applications, solid crystal solder paste not only provides mechanical fixation, but also assume the important role of electrical connection.

Red glue:

Application Scenario: Mainly used for fixing components that are heat sensitive or do not require electrical connection.For example, in the double-sided mounting process, red glue can be used to fix the components on the second side; in the camera module, red glue can be used to fix the lens mount and other structural components.

V. Summary of advantages and disadvantages

Solid crystal solder paste:

Advantages: excellent conductivity, high mechanical strength, good long-term reliability.

Disadvantages: high process temperature, high cost (especially lead-free solder paste), higher risk of damage to heat-sensitive components.

Red glue:

Advantages: low process temperature, lower cost, suitable for fixing complex structures.

Disadvantages: non-conductive, limited mechanical strength, poorer temperature resistance.