Specifications

14
Dec. 20
Mitsubishi IPM-series Application Note
7-3. Mitsubishi's Quality-Assurance Program
One of the basic goals of Mitsubishi Electric is to offer our customers quality products. As a consequence, product quality, price,
timely delivery, and service are equally important aspects deserving an equal amount of attention. Still, product quality must stand
above all others from a standpoint of customer confidence.
Quality standards in the semiconductor industry are extremely high; production of wafers is a carefully controlled, precision
process, and assembly processes are done under microscopes to assure that there are no sacrifices made in technology, or in
quality.
The following subsections outline the quality-assurance programs Mitsubishi Electric uses in its mass-production.
7.3.1 The Path to a Mass-Production Device
From research prototype, through mass-production, a serial type tests are run at each stage to assure performance and
reliability of the ultimate product. At the same time, the design drawings are also closely checked. The path from the research
stage to mass-production is shown in the flow chart of Fig.7.7 The subsections that follow briefly describe the reliability tests used
to check for device reliability.
7.3.2 Environmental Controls
The semiconductor industry as a whole recognizes the affect environmental factors have on product quality, and rigorous
standards have been established regarding the control of dust, humidity, and temperature in manufacturing facilities. The same
level of standards is also used for the various gases, and the water used in the manufacturing process.
7.3.3 Periodic Inspection and Maintenance of Manufacturing Equipment and Instrumentation
The various equipment and measuring instruments used in semiconductor production are an extremely important element of the
total process. It is therefore imperative that a periodic program be implemented to inspect and adjust these components so that
optimum precision standards are maintained, and to forestall any interruptions in the production process.
7.3.4 Quality-Control of Materials Purchases
Materials are subjected to rigorous acceptance tests using equipment such as spectrometers, helium leak detectors, etc. Before
placing full orders, thorough sample testing is done, and all problem areas are worked out before making an official decision.
Quality-control procedures at the supplier’s plant are also considered in any procurement decision.
7.3.5 Control of the Manufacturing Process
Various measures have been taken to control the elements that have a decisive influence on the quality of the product.
Measuring instruments are used to monitor water purity, atmospheric conditions, furnace temperatures, gas flow, and other
factors. Check-sheet inspections are made, and recorders keep automatic records. These records are carefully correlated with
the records kept on matters such as diffusion depth and surface density to establish proper working conditions.
7.3.6 In-Process and Final Inspections
The goals of the in-process and final inspections are twofold: the first is to assure product quality from the standpoint of outer
appearance, dimensions, structural integrity, and mechanical and electrical characteristics. The second is to feed this information
back upline to improve quality, and to reduce variations in future batches.
In-process inspections are intended to check the wafer and assembly processes, and serve two purposes; one being
self-imposed checks on the production process, the other for use as a quality-control tool. As its name implies, production
personnel to correct deficiencies they clearly recognize use the self-imposed check, and emphasis is placed on points that are
difficult to detect in completed devices. After the device is completed, it is subjected to the final inspection and the
quality-assurance inspection. The final inspection is run on all devices, and consists of testing electrical characteristics and outer
appearance. Quality-assurance personnel assume the role of the end user, and inspect samples for correct electrical
characteristics, outer appearance, and reliability before devices are packed in storage.
The flow chart for the quality-assurance program covered in the above is noted in Fig.7.9.
7.3.7 Quality Information
Mainly the quality assurance division compiles various kinds of quality information such as inspection results and
customer-supplied information. They are quickly fed back to related divisions including the production division for maintenance
and improvement of quality.
In addition, we employ computer-based, streamlined, and effective quality control systems in order to modernize the information
management.
Reliability