Improve flexibility of heat dissipation design for power devices’ embedded substrates

In recent years, the development and use of substrates with embedded dies have advanced as a high-density packaging technology, making electronic devices smaller and more integrated. These substrates are particularly favored for power modules using Si MOSFETs, such as power supplies for AI servers. This preference is due to their smaller footprints, reduced parasitic inductance, improved reliability, lower costs, and simplified wiring. However, with dies and other components densely packed within these substrates, thermal management becomes crucial, especially for high-current power modules.

Various methods have been considered to improve heat dissipation. These include increasing the number of thermal vias connecting the embedded die to heat dissipation pads or forming heat dissipation pads directly on the back of the embedded die by filling cavities in the insulation material with copper plating. However, these methods can be challenging to achieve with conventional thermal curing insulation materials.

As a solution, Resonac presents its photosensitive interlayer insulation film PV-F (Photo Via Film). PV-F leverages photolithography to form insulation layer patterns, enabling the creation of large cavities that are difficult to achieve with laser drilling, or numerous thermal vias without compromising throughput. This technology enhances the flexibility of heat dissipation design by forming thermal vias and heat dissipation pads directly on the embedded die through copper plating.

 

Innovative Solution

Improved Flexibility of Heat Dissipation Design by Large Cavities

In traditional thermal curing interlayer insulation prepregs or films used for insulation between layers in embedded die substrates, laser drilling was typically employed to create vias. However, laser drilling can only form vias up to approximately φ350μm, making it inadequate for creating large cavities necessary for heat dissipation pads, which benefit thermal and electrical conduction. An increase in the number of vias also results in decreased productivity due to throughput declines, especially when forming more than a million vias per panel.

Moreover, in embedded die substrates, dies temporarily fixed in place had to be precisely embedded with insulation material. High viscosity in conventional thermal curing interlayer insulation prepregs made accurate embedding challenging, leading to poor alignment and wiring connection issues between die pads and the substrate.

Resonac’s photosensitive interlayer insulation film PV-F, using photolithography, facilitates the formation of cavities 500μm square or larger. Filling these large cavities with copper plating enhances heat dissipation and conductivity, improving substrate design flexibility. This technology enables the formation of numerous thermal vias with small pitches without throughput declines. Due to its low viscosity, dies can be embedded at low temperatures and pressures, reducing misalignment risks and minimizing the chance of wiring connection failures.

As previously mentioned, Resonac’s photosensitive interlayer insulation film PV-F significantly enhances the flexibility of substrate heat dissipation design, productivity, and wire connectivity.

 

 

PV-F vs. Conventional Products

Product Features

Forming Small Vias and Large Cavities in a Single Process

Low Viscosity Allows Filling at Low Temperatures and Low Pressure

• ※ The data shown are representative values that represent examples of the results of measurements, calculations, etc., and are not guaranteed values.

Update date: 19 September, 2024