Encapsulants & Underfills

What is the main difference between liquid encapsulants and molding compounds?

Liquid encapsulants and Epoxy molding compounds are generally two sides of the same coin. They are a thermosetting mixture of polymeric resin, a hardener and some fillers that come in both liquid and solid (pellets/powder) forms.

• Liquid encapsulants are dispensable materials that are preferred for flexible, lab-scale projects that need constant changes and alignments. They are using an easy and cheap dispensing system that is ideal for flexible projects with lower throughput. Research, development, and advanced packaging are definitely favoring this liquid encapsulation that facilitates innovation.
• Epoxy molding compounds are, as the name implies, moldable materials. They are commonly used with transfer (and rarely compression) molding. Transfer molding is a fixed, controlled, and expensive process. You need very specific mold designs and sophisticated equipment that can only be used for a single package. This makes this process completely rigid and requires a very large initial investment and a definite package design.

What would be the effect on the product's performance after the guaranteed shelf-life?

Effects of using 1-part epoxy after guaranteed shelf-life:

• Viscosity and Flowability Changes : Viscosity can change over time due to premature crosslinking even while stored. Crosslinking occurs when the polymer chains within the epoxy network form strong chemical bonds, resulting in a more rigid structure. As a result, its viscosity could increase beyond the optimal range. High viscosity can lead to difficulties during application, affecting the encapsulation process. Furthermore, a higher viscosity epoxy may not flow as easily into intricate spaces or around components, potentially compromising the encapsulation quality.
• Decrease in bonding performance: After the guaranteed shelf-life, the bonding performance of an epoxy may decline. Factors contributing to this include: (1) Incomplete Curing: Premature crosslinking can lead to incomplete curing. The epoxy may not achieve its full strength, impacting the bond’s durability. (2) Reduced Adhesion: Aging epoxy may lose its ability to adhere well to surfaces. This can result in poor bonding between the encapsulant and the components. (3) Chemical Changes: Over time, the epoxy’s chemical composition can alter due to exposure to environmental factors (e.g., temperature, humidity, UV light). These changes may affect its compatibility with different materials. (4) Weakened Mechanical Properties: Aging epoxy may become more brittle or less flexible, affecting its ability to withstand mechanical stress or thermal cycling.

Are there any SVHC free encapsulants?

There are SVHC (Substances of Very High Concern) free encapsulants available. For instance, Loctite Eccobond 7010C DAM is an SVHC free dam encapsulant with high purity, designed for glob top applications and the encapsulation of bare wire bonded semiconductors. It operates at temperatures ranging from -40 to 150ºC and has good crack, chemical, and thermal resistance, along with low thermal expansion.
Another product, Loctite Eccobond 7010C FILL, is an SVHC free fill encapsulant suitable for high operating temperatures and is designed for use as a potting or encapsulation resin protection for stress-sensitive electronic components. It is formulated with a low thermal expansion and high Tg, making it ideally suited to survive severe thermal shock conditions with a high resistance to micro cracking. These products are examples of SVHC free encapsulants that are also REACH compliant, ensuring they meet strict European Union standards for chemical safety.

These products are examples of SVHC free encapsulants that are also REACH compliant, ensuring they meet strict European Union standards for chemical safety.

How can we maintain the optimal performance of the encapsulant?

To maintain optimal performance:

• Follow Shelf-Life Guidelines: Always adhere to the recommended shelf-life provided by the manufacturer. Using epoxy beyond this period increases the risk of performance issues.
• Proper Storage: Store epoxy encapsulants in a cool, dry place away from direct sunlight. Avoid extreme temperatures or humidity.
• Test Fresh Batches: Before critical applications, test a fresh batch of epoxy to ensure it meets the desired properties (viscosity, curing time, adhesion strength).
• Consider Alternative Materials: If an epoxy has expired, consider using a new batch or exploring alternative encapsulant materials.

What’s the recommended dispensing process to avoid the voids?

Liquid encapsulants should be applied in a controlled and consistent manner. Abrupt pouring should be avoided. It is recommended to use dispensing equipment to control material flow and allow air to escape as the material fills the package. Mold design is also a factor along with the dispense pattern being used and the dispense volume consistency.

What are the main properties to be considered when choosing the right encapsulant or underfill?

When selecting the right encapsulant or underfill for a specific application, Viscosity, Coefficient of Thermal Expansion, Cure Temperature, and insulating properties are some of the properties that should be considered.