Wafer Level Packaging (WLP) 

Wafer Level Packaging Process Flow

Wafer level packaging integrates packaging steps directly into the wafer fabrication workflow. Instead of assembling and packaging individual dies after dicing, WLP allows electrical interconnects, protection layers, and external contacts to be formed simultaneously across the entire wafer surface.

This parallel processing approach improves yield, reduces handling damage, and enables high-throughput manufacturing for advanced semiconductor devices.

Redistribution Layers (RDL) in WLP

A critical element of wafer level packaging is the redistribution layer (RDL). RDLs reroute the original bond pads on the integrated circuit to new locations that optimize electrical connectivity and mechanical reliability.

• Enables finer pitch interconnects
• Improves signal integrity and reduces parasitics
• Supports high I/O density designs
• Allows compatibility with standard surface-mount assembly

RDLs are typically fabricated using thin-film metal deposition, photolithography, and dielectric passivation processes similar to front-end semiconductor manufacturing.

What Is Wafer Level Packaging?

Wafer level packaging (WLP) is a semiconductor packaging method where all packaging steps are completed while the devices are still part of the wafer. Unlike traditional packaging, individual chips are not packaged after dicing. Instead, electrical interconnects and protective layers are formed at the wafer level.

How Wafer Level Packaging Works

The wafer level packaging process typically includes the following steps:

1. Front-End Device Fabrication – Integrated circuits are fabricated on the wafer using standard semiconductor processes.
2. Redistribution Layer (RDL) Formation – Metal layers are deposited to reroute electrical connections to new locations on the die.
3. Passivation and Protection – Dielectric layers protect the circuitry from moisture and mechanical damage.
4. Solder Bump or Copper Pillar Formation – Electrical contacts are formed directly on the wafer.
5. Wafer Dicing – The packaged wafer is diced into individual, fully packaged chips.

Types of Wafer Level Packaging

• Fan-In WLP – All interconnects remain within the original die footprint.
• Fan-Out WLP – Interconnects extend beyond the die, allowing higher I/O density.

Why Wafer Level Packaging Is Important

Wafer level packaging enables:

• Smaller and thinner semiconductor devices
• Improved electrical performance and shorter signal paths
• Lower parasitic resistance and inductance
• Higher manufacturing throughput
• Cost-effective packaging for high-volume production

Applications of Wafer Level Packaging

• Mobile devices and wearables
• MEMS sensors and actuators
• RF and wireless components
• Automotive electronics
• Medical and IoT devices

Related Pages

• Silicon Wafers
• Silicon-on-Insulator (SOI)
• Glass Wafers
• Sapphire Wafers
• Silicon Epitaxy