The die-cast copper motor rotor – a new copper market opportunity
Induction motor manufacturers have long known that substitution of copper for diecast aluminum in the rotor squirrel cage would significantly reduce motor losses and improve the electrical energy efficiency. Aluminum is readily die-cast to produce the complex squirrel cage within and around the iron laminations of the rotor. Copper is much more difficult to die-cast due to its high melting temperature which leads to premature die failure. The work reported here addresses the die life problem in die casting electrical grade copper. A number of candidate high temperature die materials were surveyed. Computer simulation of the cyclic thermal and stress gradients in dies provided insight into the “heat checking” failure mechanism and how it could be minimized or avoided. A nickel-base alloy die system preheated to and operated at ~625°C has been developed and shown to greatly extend die life compared to die steels operated conventionally. A die insert heating and insulation system was developed to make extended runs possible. Copper motor rotors were die cast over a range of machine operating parameters in joint effort with several motor manufacturers. Motor test results showing the predicted 15 to 20% reduction in motor losses and reduced motor operating temperatures are presented.
Design and Development of Rotor Quality Test System for Die-Cast Copper Rotors
It is well known in the market that the copper rotor motor can give good efficiency at par with the new era motors, and can handle higher temperatures to qualify for electric vehicle application. Being a heavy metal, die-cast copper rotor manufacturing needs absolute care for faithful rotor production. In this paper, the common faults in copper die-cast processing are identified and sufficient monitoring methods are suggested in a three-stage inspection. The final stage consists of a rotor quality test system, which detects most of the problems found in copper die-cast rotors. This rotor quality test system analysis helps to optimize the rotor manufacturing process and avoid the circumstances of fitting an inferior rotor in the motor assembly.
Chip scale packaging using chip-on-flex technology
An increasing number of electronic designers, fabricators and users see Chip Scale Packaging (CSP) as a way to obtain the benefits foreseen in multichip packaging and Chip-on-Board (COB) without the problems and limitations currently associated with each. The Chip-on-Flex (COF) multichip packaging technology has been demonstrated to be applicable to single chip packages that meet chip scale packaging goals. This paper looks at the Chip-on-Flex Chip Scale technology and addresses issues including the process, structure, assembly, yields and reliability.