YANMAR Technical Review
Prior-Evaluation of Electrical Components to Improve Product Quality～Efforts in the Quality Analysis Center～
In recent years, Yanmar's products are equipped with many electrical components. Securing electrical component quality has become more important to have customers use our products safely and comfortably. To prevent the occurrence of product quality problems in a market, electrical components are tested during product development stage.
This article describes our prior-evaluation methods and internal system with actual examples.
Final products produced and marketed by Yanmar, such as tractors, construction machinery, and generators, contain thousands of individual parts, with some being off-the-shelf while others are specifically designed for Yanmar. In either case, it is essential that their quality shall be secured.
Along with JIS and other industrial standards, Yanmar also applies its own in-house Yanmar industrial standards (YIS) to parts quality evaluation. This article describes how evaluation of electrical components is conducted in advance.
2.Prior-Evaluation of Electrical Components
2.1.Characteristics of Electrical Components Evaluation
As noted above, final products are made up of thousands of parts. In the case of electrical components, however, these parts contain furthermore tens or hundreds of individual parts. In the case of parts that incorporate a microcomputer tens of thousands of lines of software code are included. The greater the number of parts, the more possible locations there are for a failure, with a diverse range of failure modes. This means that there are a large number of test evaluation items on electrical components.
2.2.Operating Environment for Electrical Components
While Yanmar designers do their best to locate electrical components in the most favorable environment, they still face very harsh environments compared to home appliances. Along with things like temperature, vibration, and rain water, static electricity and other forms of electrical noise are a major threat to electrical components. Despite being subject to these environments, components are expected to operate trouble-free for a decade or more.
2.3.Example of Electrical Components Assessment
The following uses the example of a component that includes an electronic circuit board to describe how evaluation is performed.
Dozens of different test evaluation items are performed. Each test item has a number of judgment criteria.
Among the above, the following describes thermal shock test example.
The ambient temperatures of the parts fitted to machinery used outdoors can range from −40℃ on winter mornings to more than 100℃ when operating under load during midsummer. Thermal shock test is one of environmental tests that checks how well electronic parts can resist changes in the ambient temperature.
The test is performed using a thermal shock testing machine capable of making rapid temperature changes that impose expansion and compression stresses on the part under test. The part is placed in the machine for a specified number of cycles of high and low temperatures, then taken out and subjected to operational checks and degree of degradation check.
The method used to evaluate the degree of degradation include measuring the current/voltage (I-V) characteristics of the part or examining it using X-ray, electron microscope, or other means. An example is described below.
Use of curve tracer to evaluate current/voltage characteristics of parts
While a functional check only indicates when electrical parts have broken entirely, measuring the I-V characteristics of parts on the circuit board can be used to check whether they have suffered any degradation.
Photographing by X-ray (example)
An X-ray machine can be used for non-destructive observation of the internal structure of a part under test.
* Part needs to be cut in half when viewing in detail is required.
Photographing by microscope (example)
Locations that are difficult to photograph by X-ray (such as locations covered by thick metal or cracks a few microns in size) are viewed by cutting the part in half and examining with a microscope. The images below show cross-section observations of circuit board parts and solder joints.
While evaluation of electrical components is conducted by the development departments of each operational division, a quality analysis center for conducting evaluation of parts based on the request from the operational divisions has been established to conduct testing evaluation and establish evaluation criteria in greater detail at the development stage. The center also analyzes and investigates the causes of product defect occurred in the market.
The increasing importance of electronic control in the products means that the quality assurance of electrical components is a major subject. To minimize lost opportunities for customers caused by machine-down, Yanmar's quality analysis center aims to contribute to further improvements in product quality through the installation of new equipment and continued trials of new evaluation technology.
The original technical report is written in Japanese.
This document was translated by Research & Development Management Division.