CoWoP: Game-changer beyond CoWoS—Or, hype? PCB makers stay skeptical

Fueled by booming demand for advanced packaging like CoWoS, a new report from China’s Wallstreetcn is turning heads with claims of a breakthrough “CoWoP” (Chip on Wafer on PCB) tech—mounting chips directly onto PCB mainboards via mSAP processes, skipping IC substrates entirely. 

However, Infotimes suggests that PCB manufacturers are taking these bold claims with a grain of salt, and securities firms say NVIDIA’s Rubin Ultra likely won’t adopt it.

CoWoP in a nutshell
As Wallstreetcn points out, CoWoP technology streamlines chip packaging by removing several traditional components from the CoWoS process like the package substrate and BGA (ball grid array) solder balls. Infotimes, on the other hand, breaks down the process into two main steps:

Die-to-interposer connection using micro-bumps: This process involves mounting the bare chip (die) onto a silicon interposer using micro-bumps, enabling high-density connections between the chip and the substrate.

Direct PCB mounting: The entire chip-and-silicon assembly is then mounted directly onto multi-layer PCBs, bypassing traditional organic packaging substrates entirely.

What makes this approach particularly intriguing, as per Infotimes, is how it reimagines the role of PCBs. Instead of merely providing electrical connections, the PCB takes on additional responsibilities by incorporating fine-pitch redistribution layers (RDL) through advanced HDI or MSAP/SAP processes, which enhanced functionality aims to maintain signal integrity and ensure proper power distribution, the report adds.

As highlighted by Wallstreetcn, by leveraging mature, large PCBs to replace costly ABF/BT substrates, CoWoP significantly cuts material and manufacturing costs while speeding up mass production and shortening delivery times. While directly embedding chips, silicon interposers, and multi-layer HDI/MSAP redistribution layers onto the PCB, the method could reduce packaging complexity, the report adds.

Challenges persist as PCB makers remain skeptical
However, TrendForce observes that CoWoP is still at very early stage and uncertain. Infotimes, citing PCB manufacturers, notes that with substrate technology already mature and cost-effective, customers see little reason to switch.

On the other hand, Wallstreetcn also notes that the actual costs don’t vanish—they just relocate. While CoWoP eliminates expensive organic substrates (ABF) and traditional packaging steps, these savings shift to demanding higher-tech “platform PCBs” and more complex “die-on-board” assembly processes, the report indicates.

Top U.S. securities firms reportedly believe that NVIDIA’s Rubin Ultra is unlikely to adopt CoWoP technology. The key reason is that Rubin Ultra will require a significantly larger ABF substrate area with more layers than its predecessor. 

To match the performance of current ABF substrates, CoWoP would need PCB line width and spacing to shrink from the current 20/35μm to below 10/10μm—an engineering challenge they consider extremely difficult with today’s PCB capabilities.

-- Source: TrendForce, Taiwan.