Baking thermal effects

Some general conclusion from these studies are (1) Cu/PI TFML structures have excellent thermal and mechanical stability under extremes of temperature, humidity, and radiation (2) the adhesion of polyimide is highly dependent on interface chemistry and surface preparation (3) PI rapidly absorbs and desorbs water, which has an appreciable effect on its dielectric properties and thus the electrical charactersitics of TFML interconnections the electrical design tolerances must accommodate these variations or the package must be hermetically sealed (4) properly baked and sealed TFML packages can maintain MIL-STD internal moisture levels of less than 5000 ppm at 100°C. 

In most countries, use of synthetic antioxidants is regulated and the safety of the compounds involved has been tested based on long-term toxicity studies. The ability of an antioxidant to withstand thermal treatment (e.g., frying or baking) and to retain sufficient stabilizing activity for the food (fried or baked) is termed as carry through property. Table 6 provides a summary of physical properties of commonly used synthetic antioxidants. Several researchers have smdied the effectiveness of these compounds in suppressing lipid oxidation in fats and oil, and Tables 7 and 8 provide comparative effects of synthetic antioxidants (82). 

Chemical disinfection, on the other hand, is not as effective in killing organisms as thermal disinfection, but has several advantages It is simple to use, thereby ensuring greater user compliance. Lens life is longer with chemical disinfection as lenses are not subjected to daily heat treatment. The method results in fewer deposit problems as surface debris left on the lens surface due to improper cleaning is not baked by heat. 

Postexposure bake of the wafer. A postexposure bake (PEB) improves contrast of the photoresist before its development. The PEB process causes three effects 1) diffusion of the PAC 2) solvent evaporation and 3) thermally induced chemical reactions. In general, the dissolution rate of a resist decreases as a function of a PEB temperature. PEB becomes more important for the photoresists with a chemical amplification (CA) feature. The photoresists need the PEB to complete chemical reactions initiated by exposure. 

The effects of thermally driven diffusion of active chemical species within the resist during the postexposure bake are modeled with appropriate diffusion... 

To account for the effect of postexposure bake in reducing standing waves through thermally driven diffusion of the photoacid, lithographic simulators employ models... 

As an example. Figure 4.26 shows the effect of a thermal treatment carried out at 50, 70 and 90 °C on a VIP prepared with an open cell foam and an aluminium foil-containing laminate. The foam was pre-baked at 150 °C for 20 minutes and no absorbent was used. 

---