Space and avionics applications need a high level of reliability as they face extreme conditions in space. In order to develop components qualified for this application, engineers need to design high reliability into these products. This interview looks at how they achieve high reliability for these products, and also on how a product is qualifies for space applications.
Wolfgang Kuebler, senior marketing manager – high reliability products, Infineon speaks with Abhishek Mutha from EFY.
Q. How is high reliability achieved for products incorporated for space use? What kind of tests and processes are carried out?
To achieve solid reliability, we take silicon wafers from stable production and pack these devices into hermetically sealed ceramic packages. This whole process has to be deeply evaluated and qualified. After the component is manufactured there is the so-called screening which consists of different tests including temperature cycling, burn-in and hermeticity checks. During this screening, the electrical parameters of the component are tested several times to make sure they stay the same. For space applications, a working lifetime of 15 years is expected and there is absolutely no mortality allowed.
Q. What are the kinds of design challenges you face while manufacturing HiRel components?
Manufacturing has to follow very strict rules. To be a space supplier, you need to be certified by a space agency. In Europe, it’s the European Space Agency (ESA) who does certification. They check our production facilities, do paper and factory audit and check if every process is documented. There is a lot of visual inspection in between. Normally, it is much easier to manufacture a component but for space, every step in manufacturing is visually inspected and verified.
Q. What are the kinds of customer challenges that you come across? Are the customer requirements very dynamic in nature?
No, they are not so dynamic. Once a module is designed, a customer would want to stay with it as long as possible. So the major challenge is to produce the component in the required space quality for the next 20 to 30 years even if it is just a few pieces per year.
Q. Could you talk about the kind of rules and regulations for a HiRel product to be qualified for space and avionic applications?
The ESA (European Space Agency) have a qualified part list. Our target is to enter this list because that way the customers trust and pick us. To get a component on this part list, you have to do a so-called evaluation of the components. Even during the build up of the component, the space agency has the right to do a pre-inspection before closing the package of the component. After the component is sealed, evaluation is started. During evaluation, various test are performed like a 3000-hour burn-in or lifetime test. Shock, vibration, temperature and step-stress tests are some other tests performed.
Q. Could you elaborate on how these tests are done?
Temperature step stress test is one where you bring the component to work and increase the temperature in steps of 20 degrees every week until it basically breaks thereby checking the limit of the component. In a power step stress test, power is increased in equal steps. So with all these limits, the specifications are built. So if the component has a limit of 10 watts, the specification would say ‘you are allowed to use this product up to two Watts’. What I mean to say is there is always a very big degradation. Then the components are sent for qualification where you test all the limits that have been set. For instance, if the specification states two watts then the product is tested once more at two watts. Any major variations during this test are noted down. After qualification come all kinds of paper work. Finally, after the entire test, the product is approved and certified. Every two years, a re-certification needs to be done.
Q. That seems like a really long process. So what’s the average time it takes for a component for space uses to be available from scratch?
Let’s say when you have a technology and using that you create a product, it could take roughly one to one and a half year. The evaluation and qualification takes about three-fourth of a year or even one year, and including all the paper work it comes to about one and a half years. If you start a project from scratch, or develop a new technology, it could be several years; probably three to five years.
Q. Could you brief us on the kind of technologies that Infineon works with to create these HiRel products?
For the silicon microwave transistors, we have different kinds of bipolar technologies. For RadHard PowerMOS transistors, we use a derivate from the Infineon unique technology called CoolMOS, which is also widely used in power supplies.
Q. Could you throw light on Standard PowerMOS versus Radiation Hard PowerMOS for space?
All electronic devices that are sent to space have to be radiation hardened. Power MOS are very sensitive for radiation effects and the breakdown of such components is very severe and can cause the failure of a complete space mission. Therefore, the main focus on radiation hardness is for such components. Two effects have to be considered – Total Ionisation Dose (TID) and SEE (Single event effects by heavy ions). To cope with the space requirements, Infineon developed our own 250V Radiation hard PowerMOS technology, which is worldwide benchmark for its TID and SEE hardness in combination with best in class electrical parameters.
Q. Apart from TID & SEE, are there any other extreme conditions that HiRel components undergo in space?
Most extreme conditions that the components may see during the lift off and transport in space to the final destination are extreme temperatures and vibrations.
Q. Talking about your RadHard PowerMOS, why do you claim that by incorporating this Infineon devices can beat all other devices existing in the market?
Infineon Radiation hard powerMOS offers the best in class Radiation hardness and electrical parameters such as a low Rds (on) and a low Qg, which helps the customer to make a very efficient design. Secondly, for space components very short lead-time is an important factor. We are talking here about 12 weeks for Engineering devices and 18 weeks for Flight devices. Last but not least I want to mention the Export regulations. As Infineon is a European country, Infineon devices do not have such export regulation which makes life much more easier for the manufacturer to buy Infineon components. You might ask now why I do not talk about high quality at this point. It is easy because the quality has to be there in any case and if we at Infineon would not be sure about our quality we would not supply components to the space market!
Q. What are the requirements and needs of the space industry today?
The major requirement is to get the components from a reliable supplier with the expected high quality, as well as a moderate lead-time and from a vendor who is not under any export regulations of the country of origin. Lead time is a special issue and is getting more and more important because in space, as the complete design cycle gets shorter, the module manufacturers cannot wait 40 or 50 weeks for the components. However, a lot of space components have lead times in that range.