KARIYA, Japan – Denso Corp., Japan’s largest automotive supplier, has a reputation for producing some of the industry’s smallest components.

And the center of Denso’s miniaturization activities is its Kota plant here.

Located 30 miles (48 km) southeast of Nagoya in Aichi prefecture, the plant is a comprehensive car-electronics manufacturing complex making everything from monolithic and hybrid integrated circuits (ICs) to sensors and electronic control units (ECUs).

Since opening its doors in 1987, Kota has grown in proportion to demand for car electronics and today consists of four buildings on its 70-acre (28-ha) site with 2.4 million sq.-ft. (223,000 sq.-m) of floor space.

Included in the operations is a new ¥17 billion ($147 million) wafer-processing facility for making IC wafers used in automotive ECUs. The 3-story facility, which opened in June 2006, joins an older wafer plant on the site. Denso estimates the new facility will produce 10,000 8-in. (20-cm) wafers per month when it reaches full capacity in 2010, adding to the 23,000 6-in. (15-cm) units produced in the older plant.

Kota turns out 120 million ICs, 60 million ECUs, 60 million sensors and 9 million instrument clusters annually. Along with a facility in Takatana, it is one of two Denso plants in Japan making clusters.

Of Denso’s ¥720 billion ($6.2 billion) in global electronics sales last year, the lion’s share originates at Kota. In addition, Denso produces electronics at its Takatana and Daian plants in Japan and at more than a dozen facilities overseas in the U.S., Mexico, India, China, the Philippines, Malaysia, Taiwan, South Korea, Australia and Spain.

ECUs produced at Kota go into the full range of Toyota Motor Corp. vehicles, from the luxury LS 460 and Crown Majesta to the bread-and-butter Corolla and Vitz. Included are ECUs for powertrain, body and driving-control systems – specifically for engines, transmissions, airbags, antilock brakes, remote security, climate control and car navigation.

For the new LS 600h and LS 460, Toyota’s premier luxury sedans, the plant produces power supply management and pre-crash seatbelt ECUs; stereo image processing and remote security ECUs, both industry firsts; an inertia sensor with inclination-detecting capability and a card key-with-circuit board, also industry firsts; and front millimeter-wave radar.

Approximately half of Denso’s ECU sales are tied to Toyota.

In its extensive sensor lineup, Kota produces 2 million acceleration sensors and 2 million pressure sensors per month, high-pressure types finding use in car air conditioners, oil coolers, power-steering systems and continuously variable transmissions. It also makes 1 million speed sensors monthly and produces gas-pressure and solar sensors in smaller volumes.

Meanwhile, Denso makes all types of ICs at Kota, including small-online and quad-flat packages among monolithic types, plus regulators, igniters and fan motor controllers in its hybrid IC lineup.

Since Denso began IC production in the mid-1970s, it has tightened the design standard from 10 microns to 0.35 micron today.

“In the future, we must further improve noise, voltage and temperature performance. But we’re not going to reduce size,” says Ryouichi Kubokoya, manager of Kota’s wafer plant. “Size won’t change.”

Denso subscribes to a single defect standard, Kubokoya adds. “One defect is accidental. Two defects aren’t,” he says.

Contributing to the plant’s exceptional quality levels are clean room facilities that can detect particles under 0.1 micron.

Inside Kota’s main plant, Denso assembles ECUs and sensors. The 4-story structure looks like a school auditorium with machines, rather than chairs, lined up in rows on polished linoleum floors and automated guided vehicles moving between the lines carrying materials and finished components.

In the plant’s fourth-floor sensor assembly shop are some 30-40 lines, including three high-speed automated lines that make high-pressure refrigerant sensors for car air-conditioners. These devices provide precise temperature and idling control to improve cabin comfort and raise fuel efficiency.

Lines vary in length and automation based on customer demand, with small-volume devices assembled on shorter, more labor-intensive “cell” lines and larger-volume products, such as air-conditioner pressure sensors, on longer, virtually unmanned lines. The only personnel seen on the three air-conditioner lines are supervisors and inspectors.

Each of the three lines, the newest of which was installed early this year, turns out 300,000 units per month, varying by car model and nameplate. In addition to Toyota, Denso supplies Daihatsu Motor Co. Ltd., Honda Motor Co. Ltd., Mitsubishi Motors Corp., BMW AG, Daimler AG, PSA Peugeot Citroen and General Motors Corp.

In fact, the plant’s main customer is not Toyota or any other auto maker, at least not directly. Instead, it mostly supplies Denso’s Nishio facility 10 miles (16 km) away. Nishio, the world’s largest car air-conditioner plant, turns out more than 7 million units annually, half of the supplier’s global total.

Meanwhile, the sensor shop, which runs on two 12-hour shifts employing 150 people each, is treated like a clean room where employees are required to wear plastic coats and antistatic covers for their shoes.

Defect rates after final testing - which includes functional testing at a range of temperatures from low to high, plus a series of electrical tests – are less than 0.05 parts per million.

Kota’s total workforce, including operators in the IC and ECU plants, numbers 4,600 people, about a third of which are administrative.