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Interview: Our Core Competence is fine-pitch Contacting
Yamaichi Electronics develops and manufactures contact and test solutions for semiconductors and electronic modules. Headquartered in Japan, the company employs around 3,500 people worldwide, with some 220 employees in Europe. The European headquarters, including a development department for custom solutions for burn-in, development and production testing, are situated in Munich, Germany. There is also a production facility in Frankfurt an der Oder, Germany. We spoke with Bernhard Stolz, Product Manager for test contactors and contacting modules at Yamaichi Electronics Deutschland GmbH.
AaT: What are your company's most prominent products, and what are they used for?
Bernhard Stolz: Yamaichi is a Japanese company that began producing burn-in and test sockets, mainly for tubes and transistors, in 1956. In 1991, Yamaichi acquired the German company Connector Service GmbH, which it expanded it under the name Yamaichi Electronics Deutschland to become its European headquarters.
Today, our product range primarily covers test sockets for a broad range of semiconductor package types and test systems for electronic modules. These are used for development, production and active burn-in tests. We have our own development facilities in Munich and Tunisia, while in Frankfurt an der Oder we manufacture custom test fixtures comprising the actual contacting and a mechanism for fixing the semiconductor component or module. The contacting for modules is usually effected with our fine-pitch probe pins via the connector (COMExpress), whereby a pitch of 0.5 mm is now standard. The test fixtures are mainly used at the production stage, namely for post-assembly functional tests. Another important application area is active burn-in testing. For the most part, this takes place in the automotive sector, where huge numbers of assemblies are subjected to parallel testing at 85°C over a certain period of time. Our customers also use such test adapters for installing software or firmware.
AaT: What are the key factors behind contacting solutions like these?
Bernhard Stolz: At the production stage, a long service life for the contacts and test adapters in particular is absolutely crucial. With our technology incorporating spring probe pins, we can achieve up to 50,000 or more cycles. A normal connector, on the other hand, would last a maximum of between 30 and 50 cycles with careful use. When our test adapters reach the end of their interface service life, we offer a refresh service. Since all the parts are screwed together, worn components or contacts can be easily replaced. This means that what the customer gets back within a short space of time is practically a new test adapter.
As a rule, contacts for the power supply and for high-frequency or propagation delay-critical signals are incorporated in our test adapters as well. In the case of high currents, three or four pins are usually connected in parallel to avoid exceeding the current limit for the contacts. With high-speed interfaces, such as PCI Express and USB 3.0, it is necessary to coordinate the propagation delay of the signals. We achieve this with a built-in rigid/flex circuit board, with which we can control the line impedance. For this, we have a dedicated development team which creates the best possible solution in collaboration with the customer.
AaT: Does Yamaichi manufacture the spring probes as well?
Bernhard Stolz: Our parent company in Japan has being producing spring probes for about ten years now. However, we do also use pins from other manufacturers in our test adapters if we can't offer a suitable solution, and to this end we have been cooperating with various suppliers for some years. Our spring probes consist of two, three or four parts and have a length of around 7 mm in our test adapters. The smallest pins are only 2 mm long and have a diameter of 0.22 mm. We use a nickel-plated copper beryllium alloy, which is impervious to contamination and has a life of about 500,000 cycles, as the base material for our pins.
The spring probes comprise two, perfectly matching machined parts. A great deal of know-how flowed into the manufacturing technology to achieve the requisite precision. Some modules have connector interfaces in a fine-pitch grid and up to 115 pins in one row. The reference contacts have to be aligned extremely accurately, and certain tolerances also need to be compensated for over the long interface. Our production team has around seven years' experience in this area and cutting-edge expertise here in Europe.
AaT: What should the purchaser of a test adapter look out for in particular?
Bernhard Stolz: One of the most important criteria is signal integrity, which means that the signal at all the pins should be distorted as little as possible by the test adapter. This isn't always easy to achieve, because a module can contain greatly differing lines, such as for the power supply, but also for differential, high-frequency, or fast digital signals. Very short conductor paths are not always the answer, but sometimes a lot of know-how is needed as I have already explained in conjunction with signal propagation delays. Additional small air channels are occasionally required between the signals for isolation.
However other aspects, such as the mechanical structure of the test adapter, also play a key role. How does the customer want to plug the module in, and is there enough space for the mechanics? Finally, it obviously also comes down to the number of units that are to be tested. Does the customer only want to test a few modules, or perhaps some 50,000 units a year? This means it's not just a question of the right technology, but also of economic viability. Consequently, we tend to sell extremely customer-specific solutions.
AaT: Thank you very much for talking to us!
The interview was conducted by Herbert Hoenle.
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