The reason is simple.

・Scaling (Moore’s Law) is approaching its limits

・Wiring delay, power, and heat constrain performance

・A chip alone cannot break through these limits

→ The competition is about how to connect, how to cool, and how to transport data.

Vertical Stacking with TSVs

In 3D packaging,

・Logic × logic

・Logic × memory

・Memory × memory

are connected directly in the vertical direction.

Advantages:

・Shortest wiring

・Minimal latency

・Maximum bandwidth

Challenges:

・Heat dissipation

・Reliability

・Yield

→ Practical adoption is progressing step by step.

Hybrid Bonding

Without using solder,

・Cu-Cu

・Insulating film to insulating film

are bonded directly.

Features:

・Pitches of a few µm or less

・Extremely low resistance and delay

・A key technology for 3D stacking

To go beyond the limits of electrical wiring, technology that carries data with light is coming into full swing.

Why Optical I/O Is Needed

・Losses in electrical wiring increase with distance

・Power consumption rises sharply

・Speed improvements are hitting a ceiling

Optical I/O achieves:

・Ultra-high speed

・Low power consumption

・Long distances

all at the same time.

Co-Packaged Optics (CPO)

・Optical engines are built into the package

・Directly connected to switches and AI chips

Research and implementation are progressing rapidly for data center applications.

The power consumption of AI chips has already exceeded the limits of air cooling.

Direction of evolution:

・Cooling directly beneath the die

・Microchannels

・Packages with circulating coolant

Features:

・Cooling performance on a completely different level

・Suppression of temperature non-uniformity

Challenges:

・Leakage risk

・Reliability evaluation

・Manufacturing and maintenance costs

In future packages,

・Power delivery

・Cooling

・Optical I/O

can no longer be treated separately.

What is needed:

・Electrical × thermal × optical × mechanical

・Complete co-design

The package will become a small data center.

In advanced packaging:

・Foundries are bringing back-end processes in-house

・OSATs are concentrating on high-value-added areas

The axis of competition is changing.

Going forward, the companies that survive will be:

・Companies that can collaborate technically

・Companies with an understanding of systems

Fields in which Japan has strengths:

・Materials (resins, substrates, adhesives)

・Precision processing

・Reliability evaluation

・Equipment technology

3D, optics, and liquid cooling are a world of materials × reliability.

It is an area where Japanese companies can once again make their presence felt (or so we hope).

・After scaling comes three-dimensionalization and integration

・3D stacking and hybrid bonding are key

・Optical I/O goes beyond the limits of electrical wiring

・Liquid cooling is an essential technology for the AI era

・The package will become “the system itself”

1.Why will 3D packaging become important in the future?

2.What is the biggest reason optical I/O is needed?

3.What is the biggest challenge for liquid-cooled packages?

 

Column Supervisor: Koji Kakumoto (President, OTIS Co., Ltd.)

After studying abroad and working in planning and development at a trading company, he joined OTIS Co., Ltd. in 2011. While primarily working in the Corporate Planning Department, he has also served concurrently in manufacturing and technical divisions, and since 2018 has served as President, working to drive business growth and strengthen the organization.

 

This article is a general technical explanation intended for educational purposes and does not refer to any specific company, product, or technology.