A high-efficiency transformer-in-package isolated DC-DC converter using glass-based fan-out wafer-level packaging

Citation

L. Cheng, Z. Chen, D. Yu et al., A high-efficiency transformer-in-package isolated DC-DC converter using glass-based fan-out wafer-level packaging, Fundamental Research xxx (xxxx) xxx.

Keywords

• Isolated DC-DC converter
• Transmitter (TX)
• Receiver (RX)
• Transformer
• Fan-out wafer level packaging (FOWLP)
• Power density
• Efficiency

Brief

This article presents a transformer-in-package solution for isolated DC-DC converters using glass-based fan-out wafer-level packaging, which enables high power density and efficiency.

Summary

The article presents a novel solution for an isolated DC-DC converter, called transformer-in-package (TiP), which utilizes glass-based fan-out wafer-level packaging (FOWLP). This approach allows the primary and secondary coils of the transformer to be built directly into the package using redistribution layers (RDLs), eliminating the need for a separate, bulky transformer chip. This results in a more compact design with higher power density and improved efficiency compared to traditional methods.

Here are the key advantages of the TiP solution highlighted in the article:

• Reduced Cost and Size: By incorporating the transformer into the packaging, the TiP solution eliminates the cost and space occupied by a separate transformer chip, leading to a smaller overall form factor and reduced manufacturing expenses.
• Improved Efficiency: The use of thick, low-loss RDLs in the FOWLP process for creating the transformer windings results in a higher quality factor (Q), minimizing energy losses and leading to higher conversion efficiency compared to converters using traditional silicon-based transformers.
• Higher Power Density: The compact design of the TiP solution, enabled by the integrated transformer, allows for a much higher power density compared to converters using conventional packaging techniques.

The article describes the design and implementation of the TiP isolated DC-DC converter, including the transformer design using 3-layer RDLs, the FOWLP fabrication process, and the circuit design of the power and control stages. It also presents measurement results demonstrating a peak efficiency of 46.5% at 0.3 W output power, a maximum delivery power of 1.25 W, and a maximum power density of 50 mW/mm². The authors conclude that the TiP solution offers a promising approach for developing high-performance, compact, and cost-effective isolated DC-DC converters.

Origin: https://www.sciencedirect.com/science/article/pii/S2667325823001322