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.
Semiconductor encapsulants are used to
- Protect bonded dies on substrates against mechanical and chemical impacts
- Provide localized protection of sensitive components.
- Act as a wire bond dielectric and minimize corrosion
- Subsequently, allow wire-bonded devices to pass reliability targets.
Despite all their functional similarities, they have some differences that really set them apart when choosing your semiconductor encapsulation method. And these differences are mainly practical and operational.
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.
The material itself is (Kg to Kg) slightly more expensive but the set up investment cost is minimal and can be used for multiple projects.
On top of that, liquid encapsulants can cure in much lower temperatures(enabling sensitive components) and can achieve flatter and thinner packages. The highest that you can go if you stack multiple dams is something around 1mm. All these aspects along with the minimal wire sweep lead the charge towards miniaturization and makes them the encapsulation materials of the future.
Epoxy molding compounds
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.
These materials cure in higher temperatures and because of the way the transfer process works, they make larger and thicker packages. Finally, because of the transfer pressure and the epoxy flow through the gateways, the packages are prone to wire sweep.
But it is not all dark and gloomy. Molding compounds are cheaper than their liquid forms and once the equipment is set up the overall process becomes cheaper and potentially faster. That’s why transfer molding is ideal for standardized and finalized mass production packages.
So why would anyone choose molding compounds over liquid encapsulation? Well, it is not a contest and these are materials for very different applications. To summarize, small productions, flexible design and lower cure temp favor liquid encapsulants. Mass production, rigid design and higher cure temp favor molding compounds.
Liquid encapsulants such as Henkel’s SVHC Free 7010C DAM & FIL are used for Chip on board or wafer level encapsulations (LCM1000AF). Semiconductor molding compounds such as Hysol’s GR750 and GR9810-1PF on the other hand are the way to mass-produce millions of Sensors, TO, DIP, QFN and high power packages. Very different needs for very different niches and designs.
Optically clear materials exist for both categories. Optoelectronic molding compounds such as TC-8020T are already used in biometric and optical emitters and transmitters. Clear liquid encapsulants like OLS-1211 are used for LED potting or glob top optical encapsulation.
Liquid encapsulation on laminate is leading the way while transfer molding is maintaining the billions of currently produced singled-out leadframe packages. Both are crucial for the advancements in technology and electronics.
Do you have an application and you are not sure what process to choose? You know your process but you cannot choose a proper molding compounds or liquid encapsulants? Please contact us and we will take you through the steps to identify or even develop a product that perfectly fits your application requirements.