Advanced Ceramic Heaters Improve IC Packaging and System Performance

The continuous increase in the consumption of semiconductor devices and the emergence of new applications in optical components — MEMS, LCD display, flip-chip, chip-onglass, and multichip modules — has created a vast demand for faster throughput and better die-bonding equipment for IC packaging. IC packaging requires a typical ramp rate of 100ºC per second to 400 to 500ºC ±2°C, and a cycle time of 7 to 15 seconds. Similarly, IC chip testing, which stresses chips between -40 to 125ºC while monitoring electrical parameters, also requires a faster cycle rate. To manufacture ICs of all types, a die bonder or die attach equipment is used to attach the die to the die pad or die cavity of the package’s support structure. The two most common processes for attaching the die to the die pad or substrate are adhesive die attach and eutectic die attach. In adhesive die attach, adhesives such as epoxy, polyimide, and Ag-filled glass frit are used to attach the die. Eutectic die attach uses a eutectic alloy. Au-Si eutectic, one commonly used alloy, has a liquidous temperature of 370ºC, while another alloy, Au-Sn, has a liquidous temperature of 280ºC.


Epoxy adhesive has a process temperature of 250ºC. In both processes, the temperature profile of the die attach material must be precisely controlled to ensure complete curing of the adhesive or melting of the eutectic materials. In addition to fast heating, uniformity in temperature over the attaching material is crucial to minimize the defects at the bond line. To meet the demanding requirements in those applications, the heating device must be able to perform reliably with the following characteristics:

* Provide a uniform temperature both during ramp up and steady state;
* Heat up extremely fast;
* Dissipate heat quickly to allow for fast cool-down;
* Have minimum dimension change during temperature cycle;
* Withstand compressive pressure during operation;
* Be highly finished with a smooth and flat surface to enable heat transfer;
* Be constructed with mechanical features such as grooves and holes for vacuum passage and/or curved surfaces;
* Have rapid sensor response time/ short sensor response time for precise control of temperature profile; and
* Operate under high-power density.