Hitachi's "PCIMEurope2016" and set up the conference using sintered copper power device packaging technology. The characteristics of this technology is, although for lead-free packaging material, but can reduce the cost of materials and improve reliability.
To as "power cycle tolerance" implementation of the reliability index, according to the results of determination of cycles achieved leaded solder past more than 10 times. Specifically, the power device (Tjmax) junction temperature is 175 ¡æ, the largest ¦¤ Tj at 125 ¡æ under the condition of implementing power cycling test, the previous leaded solder up to 50000 times, but 550000 times when using sintered copper. In implementing to 40 ¡æ to + 200 ¡æ when the thermal cycling test, cycle times to 1000 times also not problems.
In addition, utilizing the high output power of the process is not done the module (module) in railway train also requires the use of lead-free solder, and, as the output of the power module power density increase year by year, the working temperature of power device is also rising, thus requiring the use of high reliability of the welding material. As a candidate has higher thermal conductivity of materials of gold, silver, copper, etc. One of the most common is for silver nano material sintering of solder.
The copper nano granular
And Hitachi choice is copper. Due to the low thermal expansion coefficient of copper and young's modulus is high, so the company believes its mechanical reliability, so the copper. In addition, the material cost is low also choose one of the reasons why the copper.
The melting point of copper is as high as 1100 ¡æ or so, however, direct use in one piece, it is hard to as packaging material. Therefore, Hitachi decided to copper into high surface energy of nanometer particle. Will nanometer granular copper coated insulating plate at the bottom of the power components and power components, temperature and pressure through implementation of sintering to encapsulate.
With these measures, physical properties can be achieved with massive copper level, the stable state. Does not release specific sintering conditions, according to published data, however, estimate is between 250 ¡æ to 400 ¡æ implementation of encapsulation. As mentioned, after reach more than about 250 ¡æ temperature, sintering after the joint strength of 20 mpa, can achieve practical level (after) the power device in nickel plating of copper implementation of shear test results).
Without gold (Au)
Achieve higher than nickel joint strength is also an advantage of sintered copper. When using ordinary lead solder is gold plating nickel electrode components in the power of the administered after encapsulation to insulating substrate. That is, between plating layer and the insulating substrate exist lead solder. And, so when using sintered silver.
And use without sintered copper plating, can direct joint nickel electrode with insulating substrate. One of the reasons is the lattice constant close to copper and nickel, so easy to implement azimuth match. Because can reduce gold-plated, helps to reduce the cost.
The sintered copper for power module, the result shows that the module can implement switch work smoothly. The withstand voltage of 3.3 kV, rated current of the module for 1800 a. Power device of the maximum set the junction temperature as 175 ¡æ.
The development of sintered copper power module is mainly used in railway train. Hitachi does not release the sintered copper power module products used for the schedule, but in PCIMEurope meeting, there are a lot of technical post is aimed at the practical application of 1 ~ 3 years later, so the sintered copper technology also is expected to be available as soon as practical.
