Technical Innovation and Accelerated Package Development

Engineers gather around a heatmap image displayed on a monitor.
In the LSI Package Development Div.’s office at the ROHM headquarters in Kyoto, the team discusses IC packages currently under development. Using simulation data of the stresses applied to the package during the manufacturing process, the conversation intensified as each member shared their views and suggestions.

Simulation data is also created in-house.
The team's knowledge and accuracy improve by being able to visualize and share the internal state of the package in detail.

ROHM produces approx. 900 types of IC packages.
Ensuring high quality and reliability for each product is the steadfast mission of the LSI Package Development Division.

As Mr. Nishioka noted, technological innovation has driven remarkable advancements in IC development speed in recent years. Consequently, package development must also compete in terms of development speed and cost within the framework of market demands.

Of course, it is also necessary to address issues such as ▶ withstand voltage, ▶ heat dissipation, and ▶ noise resistance that arise from current trends like ▷ IC miniaturization, ▷ increased integration, and ▷ higher voltages. Furthermore, the functionality and performance of semiconductor elements continue to evolve to meet the development needs of automotive components for EVs and HEVs, as well as ICs compatible with AI technology.

The objective is to maximize the potential of these advanced semiconductor devices while ensuring they operate accurately and reliably in customer applications for many years. The recent demands placed on IC packages have become almost limitless, with expectations placed on package engineers continuing to grow.

Flip Chip Structure
Enables direct connection to the frame without the wire bonding.
Achieves high density mounting and improved signal transmission speed.

Ag Sintering Technology
Achieves high electrical conductivity with excellent heat dissipation by using silver (Ag) sintering for chip bonding.

Mr. Nishioka, who heads the elite LSI Package Development Div. comprised of fewer than 40 members, spoke with a sense of enthusiasm for the challenges they face.

Leveraging Strengths Unique to ROHM

ROHM strives to achieve sustainable growth by emphasizing not only on the results but also the process involved. This idea is directly tied to the unique organizational structure of the LSI Package Development Div.

The work is broadly categorized into ‘materials science and metallurgy’ and ‘other fields’, with members working together to support one another in areas where individual expertise may be lacking.

What we would like to highlight here is the phrase Nishioka uses: ‘Consistent communication is essential.’
Analyzing this statement reveals the deep connection with the IDM (Integrated Device Manufacturing) system that ROHM has adopted and the extensive responsibilities entrusted to each package engineer.

IDM System x Consistent Communication

The diagram below illustrates the flow of IC production, showcasing one of ROHM’s key strengths: a vertically integrated development and production system.
To ensure high quality and stable supply, all processes are carried out in-house or by group companies, and it is clear that package development plays a critical role in all phases of the process, from upstream stages to downstream operations.

Building Quality into the Design

This shows that the role of a package engineer extends beyond the assembly process, where products are physically manufactured, to significantly involve quality control during production.

When considering the importance of close communication with the personnel in charge of each process to understand why certain outcomes occur and whether they are logical, the rationale behind ROHM’s unique approach - where a single engineer oversees the entire process - becomes increasingly clear.

Mr. Nishioka says he prefers working collaboratively as a part of a team rather than independently. With a passion for leveraging people’s strengths effectively, he smiles as he mentions that his dream job would be a professional baseball manager.

ROHM’s Front Loading approach serves as a strong, unifying thread that seamlessly connects manufacturing with meticulous coordination across multiple departments.
What is important to note here is that this unwavering concept is not something that began just yesterday or today.

First and Foremost - the ‘Field’

We spoke with engineers currently on the team to hear their perspectives.

With 18 years of experience in the field, Ms. Sumitomo now appreciates the advantage of being deeply involved in every process, as it makes it easier to achiever overall optimization in manufacturing. Particularly in the wire bonding process, she is a valuable asset, leading various development projects with her advanced expertise and skills.

She believes that a flexible attitude is key to adapting to any situation.
‘If you’re going to do something, you might as well have fun doing it.’ These words likely reflect the mindset of someone who has faced and overcome numerous challenges.

In the wire bonding process alone, the number of parameter settings for manufacturing conditions exceeds 100.

Aspiring to be a physicist, he majored in physics during college.
Even now, he feels a surge of excitement when the Nobel Prize season approaches.

Mr. Nii emphasizes the importance of the ‘Three Realities Principle’ (Genba, Genbutsu, Genjitsu), that focuses on the the actual site, actual objects, and actual situations. Despite the difficulty in visiting overseas production sites, he strives to observe things firsthand and talk directly with the local staff whenever possible.

A prototype line within an experimental facility equipped to the same standards as a manufacturing plant. The future is forged through relentless study and verification.

An analysis room was established the LSI Package Development Division.
High accuracy analysis from various perspectives is required to meet the demands of modern semiconductor development.

A phrase frequently echoed by Mr. Nii and other engineers is ‘Genba, Genbutsu’ (the actual site and actual objects). No matter how technical innovation advances, how sophisticated theoretical frameworks evolve, or how precise simulations get, there will always be aspects in the manufacturing site that deviate from theory.
Their intuition seems to naturally account for such discrepancies, reminding us how heavily semiconductor manufacturing is influenced by the physical environment and external factors, that things do not always go as planned.

Next is an account of how the team united to overcome a significant obstacle.

The Challenge to Develop Pioneering Technology

In 2016, ROHM become the first in the world to develop and mass produce automotive-grade isolated gate driver ICs. These ICs perform analog control to maximize the performance of power devices installed in motor drive inverters.
A key feature is the ability to provide control while isolating the low voltage power supply on the MCU side from the high voltage power supply driving the motor. By replacing the previously used optical photocoupler in the isolated section with an magnetic-based IC coil chip, integration into a single package was successfully acheived.

An IC designed to control power devices that drive motors in EVs and HEVs.
Compared to conventional methods requiring multiple ICs, dramatic miniaturization and faster response speeds are achieved.

While studying atomic layer growth of thin films and analytical methods at university, he also honed his craftsmanship skills as part of a human-powered airplane club.

Isolated gate driver ICs are considered one of the most critical devices for next-generation mobility.
To develop these products, the LSI Device Development Div. collaborated with ROHM Hamamatsu, which is responsible for front-end processes, to take on the challenge of adopting new technologies.
For further details on this initiative, please refer to #04 Wafer Manufacturing Processes.

Relentless Pursuit of Zero Defects

Customer reactions to this groundbreaking product were extremely cautious and critical during the development phase. Automotive environments are consistently subjected to harsh conditions, including extreme temperatures, humidity, and vibration. As a result, electronic components must operate reliably and stably over long periods of time, even under challenging circumstances. What’s more, because this product directly impacts vehicle safety, it is necessary to minimize the risk of failure over extended periods as much as possible.

There were two major challenges, both related to molding, a critical step in the assembly process.
Molding involves encapsulating the completed chip with a protective material, typically epoxy resin. This ensures that the chip, frame, wires, and other components are securely enclosed, shielding them from external influences such as physical shocks, moisture, and chemical exposure.

Molding also plays a crucial role in effectively dissipating heat generated by the device during operation, helping to stabilize the chip’s temperature. For automotive components that must endure extreme temperature conditions, heat dissipation performance is directly tied to reliability.

The tablet-shaped epoxy resin is melted in the pot, pushed upward by a plunger and injected into the left and right molds.

Foreign particles and voids (gaps) inside the product can cause issues such as ▶insulation breakdown, ▶delamination, ▶cracks, and ▶wire breakage.
In the molding process, it is widely recognized in the semiconductor industry that the structural limitations of the equipment make it difficult to completely eliminate these issues, so measures such as equipment cleaning and screening inspections are typically employed. However, the question ‘Is it truly impossible to completely eliminate the occurrence of foreign particles and voids?’ was posed by a customer. This challenge became our first major test.

Using the newly developed dies on the manufacturing equipment at the test facility, we repeatedly created prototypes, conducting thorough analysis and verification.

For example, during the development process of the isolated gate driver IC alone, over 50 utility patents and design applications were filed. These encompassed everything from material properties, such as the composition and viscosity of the epoxy resin to the speed and direction of injection, and even the mechanical mechanisms of the manufacturing equipment. The resulting technology, born from extensive knowledge and an insatiable curiosity, not only met the quality demands of customers, but also holds significant potential for application in a variety of products and processes in the future.

Proving the Unprecedented

An electronic component capable of withstanding several thousand voltage for decades, all within a compact 8mm square size, was truly groundbreaking. It is understandable that the manufacturer’s representatives were initially hesitant to trust the solution.
Introducing such an unprecedented product to the market required significant effort to gain recognition.

Specifically, this effort focused on eliminating the possibility of insulation breakdown within the resin sections of the chip (between islands).

[Case Study]
Insulation breakdown between islands due to high voltage application
>20,000Vrms

An insulation lifespan testing environment was built within an experimental facility.
The setup was thoroughly verified before conducting ultra-high voltage application tests.

By repeating the above tests under various conditions, we were able to validate the reliability of the product as part of an insulation theory.

As Mr. Kikuchi mentioned, ROHM’s isolated gate driver ICs now command approximately 60%* of the global market share.

(*As of 2024, capacitive and magnetic types for traction inverters/ROHM study)

Reflecting on the development journey, it becomes evident that such achievements and results were not attained overnight. At the start of the article, we discussed package development through the lens of constant competition between development speed and cost, but this is only one dimension. In reality, we are reminded of the vital importance of an organization's inherent strength, cultivated over time.

ROHM's manufacturing spirit is undeniably rooted in the younger generation.
I hope these words, which offer a glimpse into that spirit, will act as a compass for engineers as they continue to venture into uncharted territories.