Together with the company SZ Testsysteme AG, which develops and manufactures automatic test systems for the semiconductor industry, Schroff have constructed cabinet- and climate control concepts which adhere to a standard and at the same time correspond to the demands of the test specialists with regard to quality, EMC and cooling. Test systems from SZ SZ Testsysteme, a company based in the Bavarian Amerang, is among the leading manufacturers of test systems for mixed signal semiconductor components, which can process digital as well as analogue signals and which are mainly deployed in the automobile, computer and IT/telecom sectors. The motto of the company is: standard components – ‘yes’, standard solutions – ‘no’. This means, SZ taylors their products exactly to the customers needs, but in doing so often fall back upon proven and standardised techniques, which can be enhanced by newly developed software and customer specific components.

Quality as survival factor

A test system from SZ in principle consists of a test head and a 19” cabinet (Picture 1). The semiconductor to be tested is lead by a so-called handler system (feeder automat) to the test head, that contains the analogue and digital signal and measuring techniques in order to carry out the required test sequences and to record the results. Inside the 19” cabinet are the basic units, like power and voltage sources and the complete computer units for the drivers. Via the driver unit the operator can programme, test and analyse the semiconductors.
With regard to the 19” technique SZ was looking for a partner, who could be flexible in his approach to specific requirements but at the same time offered a standard of the highest quality. “Quality is a survival factor for us”, said Mr. Günther Hartl, in charge of mechanical development at SZ. It is well known, that in the 19” technique Schroff stands for quality. The cooperation of SZ and Schroff extends over many years and has proven itself. Today Schroff does not only supply the cabinet and subrack with accessories, but also fan units and heat exchangers, which are especially developed and manufactured for SZ. Schroff too fall back upon their extremely extensive range of standard products and depending on the requirement combines this with entirely newly developed components in order to offer customers economic solutions in the shortest time possible.

Points for consideration: EMC and cooling

The main product at SZ is represented by the M3660 Falcon, a systems that has been arranged with 192 pins, which is suitable for the testing of a broad range of components. Within the framework of an extensive EMC concept SZ partly shield assembly parts directly on the backplanes, use shielded frame-type plug-in units for especially critical boards and shield the europacPRO subrack from Schroff. The other integrated unshielded components are shielded by the cabinet as a closed shield. The PROLINE-EMC-cabinet offers sufficient protection against electrostatic discharges as well as radiation to 1 GHz. A further critical subject for SZ is represented by the problem of cooling. “Our units are often positioned in the immediate vicinity of the semi conductor production, i.e. in “Clean Rooms”, continues Mr. Hartl. “Here the cost per square metre is extremely high and we have to try and minimise the dimensions of the base of the test systems. We are working continually to house more and more electronics in less space and the heat loss in the cabinet rises therefore considerably”.

Monitored fan units

With the M3660 Falcon in two 19” cabinets arranged side by side (2 x 180x600x900) up to 6 kW of heat hat to be dissipated. For this Schroff have constructed a specific blower unit with 2 radial fan units per 19” cell; as well as specific 1 U fan units with 12 individual fans per unit. The Engineers from Schroff have integrated monitoring electronics into this cabinet, which check each individual fan (cover and plug-in-unit) for functionality. If a fan does not provide the required performance, this fault is indicated acoustically and optically. The service personnel can then identify and replace this fan quickly and easily. Individual heat dissipation concept

With the even more efficient test system, M3900 Kodiak, the capacity loss cannot be controlled through air circulation. The M3900 Kodiak is based on three side-by-side PROLINE-EMC standard cabinets and a special 400 mm wide PROLINE cabinet (Picture 2). The capacity loss created by the entire test systems reaches 18 kW – a capacity with which a one to two storey two-family house could be heated. The SZ engineers therefore decided upon a closed air circuit with heat exchangers. The systems, that were on the market, did not come up to the expectations of the SZ engineers, who had plans to realise the cooling concept from the bottom to the top and not from the front to the rear. As enclosures manufacturers with core competences in EMC and Climate Control it did not present a problem for Schroff to develop the required solution. With a temperature reduction of 5°C the heat exchanger achieves a very good operating temperature (Picture 3). Per test system 6 units are used (two each in the three 19” cabinets). The air that has been cooled by the heat exchanger travels down the rear of the cabinet and is pushed back up to the top with additional 1 U fan plug-in fan units (Picture 4). The heat exchanger takes the lost heat and takes it away as warm water. The water processing is situated in the small segment of the cabinet.

“Schroff always have an open mind to our ideas – whether they are feasible or non-feasible”, concludes G. Hartl. “Everything was tested to find out whether it could be produced. In this way we have ventured onto new ground a number of times and have met the challenges”.