“Have you ever heard of square watermelons?” Chih-Hung Hung, founder and chairman of AblePrint Technology, suddenly asked me.

We were sitting at his company’s booth at Semicon Taiwan, where he was trying to explain how its latest breakthrough technology addresses the most challenging problem in advanced semiconductor packaging for nearly two decades: warpage.

There is a certain irony here. Transistors have shrunk to the angstrom scale, while advanced semiconductor manufacturing processes employ extraordinary technologies such as EUV lithography to push the limits of physics.

Yet the AI chip industry’s trillion-dollar investments are frequently held back by one of the most basic physical phenomena: thermal expansion and contraction.

What Is Warpage, and How Does Thermal Expansion and Contraction Undermine AI Chip Yields?

CoWoS structures bond together GPUs, memory, organic interposers, ABF substrates, and various other components and materials with different coefficients of thermal expansion.

When subjected to extreme heating and cooling during manufacturing, materials that expand more readily can bulge, sometimes resulting in severe “smiling” or “crying” warpage. The larger the package, the worse the problem becomes.

During the early development of CoWoS, TSMC even suffered the painful experience of achieving zero yield because of warpage. It took repeated adjustments to materials and manufacturing processes before mass production became possible.

For example, low-coefficient-of-thermal-expansion (Low-CTE) glass fiber cloth, which is now in severe shortage and has become a major bottleneck in advanced packaging, is embedded in the substrate’s core layer as a secret weapon against warpage.

The industry has even been exploring replacing the substrate’s entire core layer with thin glass. This is the concept behind glass-core substrates, commonly known as “glass substrates,” which have attracted considerable industry investment as a way to prevent warpage in larger and more technically demanding panel-level packaging.

The “Square Watermelon” Approach: Using an Oven to Solve Warpage

AblePrint has taken a different approach. It has incorporated a patented Warpage Suppression and Adjustment System (WSAS) module into its flagship product, a high-pressure oven, to apply pressure without direct contact to trays of wafers loaded into the chamber.

The principle is similar to the “square watermelons” that became fashionable in Japan during its bubble economy. Farmers placed transparent square molds around young watermelons, which would otherwise grow round, forcing them to develop into the desired shape.

Similarly, AblePrint intervenes early in the CoWoS manufacturing process, when stress is just beginning to accumulate in the materials—the so-called “in-process” stage.

“I grow alongside you,” Hung explained. The idea is to begin correcting warpage during its “adolescence.” “You have to start straightening it out before the growth period is over.”

This is the approach he recommends most strongly.

……

(To read this exclusive story in full, visit the Tech Taiwan Substack)

Have you read?

• A Strike Vote at Micron Taoyuan Could Be the First in Taiwan’s Chip Industry
• Why Nvidia, Delta, and TSMC All Need Chroma: An Exclusive Interview with CEO I-Shih Tseng
• Micron’s Pay Packages Show Just How Wide Taiwan’s AI Wage Gap Has Become

Uploaded by Ian Huang