What Is Transfer Molding and How Does It Work?

TL;DR

Transfer molding is a semiconductor packaging process that fills mold cavities with a molten molding compound to protect dies and wires. Key steps include heating the mold, loading the substrate, clamping, transferring the compound, and curing. This method is vital for producing various package types and requires precise temperature control to avoid defects like mold flash and voids.

Transcript

Hello everyone, welcome to Semicon Talk. Today let’s talk about transfer molding.  Molding is a semiconductor packaging process  to protect die and wires from environment.  It covers dies and wires by filling mold  compound and there are many different methods.  Among them transfer molding and  compression molding are 2 major methods.  Transfer Mol... Read More

Key Insights

• Transfer molding is a prevalent method in semiconductor packaging, primarily used for wirebonding, flipchip, leadframe, and laminate packages.
• The process involves heating the mold to ensure the molten molding compound fills the cavity efficiently, typically requiring a uniform temperature of 175℃.
• Key steps in transfer molding include substrate loading, molding compound preheating, mold clamping, transfer of molten compound, and curing to solidify the compound.
• Mold clamping is crucial to prevent defects such as mold flash, which occurs when excess compound spreads outside the package.
• Post Mold Cure (PMC) is essential to stabilize the molding compound chemically, completing the curing process started during molding.
• Common defects in molding include incomplete molds, mold flash, voids, contamination, scratches, chip offs, and wire sweeps, which can impact the package quality.
• The mold chase, a critical component in the process, requires precise manufacturing, abrasion resistance, and good releasability to ensure efficient production.
• Transfer molding uses pellet-type solid-state molding compounds, and cleaning the mold chase involves melamine compounds to maintain process integrity.

Summary & Key Takeaways

• Transfer molding is a widely used semiconductor packaging process that protects dies and wires by filling them with a mold compound. The method is common for various package types, including wirebonding and flipchip packages. The process involves several steps, such as heating, clamping, and curing, to ensure effective packaging.

• Key to the transfer molding process are the precise temperatures and pressures applied to ensure the molding compound fills the cavity without defects. Mold flash, voids, and contamination are common issues that can arise if the process is not carefully controlled. Post Mold Cure (PMC) completes the curing process.

• The mold chase plays a vital role, requiring precision and durability to withstand mechanical abrasion. Its design and maintenance are crucial for preventing defects and ensuring productivity. Despite its seemingly simple appearance, transfer molding is a complex process requiring careful attention to detail.