On a most basic level, packaging refers to the process in which the die is mounted and sealed onto the substrate. Various formations of silicone or other polymers are now the most often used adhesives for encapsulant and underfill material. They not only adhere the chip to the substrate, but provide a barrier coating and essential thermal and mechanical protection so that the chip can essentially perform its job in the most reliable way possible.
Some Polymer Problems
However, polymers like silicone are not perfect solution as encapsulants and underfill materials. Electronics parts and semiconductor elements alike are susceptible to all kinds of corrosion and stresses. Heat, cold, electrical instability, and mechanical stress, ionic impurities and voids where non-heat conductive air can leak in, are just some of the problems electrical engineers and electrical adhesive experts are working on as they study and improve silicone encapsulants and underfill materials and the barrier coatings that are so essential to providing the necessary chemical barriers in our electronics.
The polymer adhesives that form the broad category which encompasses silicone encapsulants, underfill material, and barrier coatings are invaluable materials for the current electronics market, especially with miniaturized consumer electronics products. They have a relatively low cost and are being improved consistently.
Underfill packaging technology fills reinforcement materials into the gap between the chip and the substrate. Some major challenges to material engineers when it comes to high performance silicone encapsulants, underfill materials, and barrier coatings have been how to get a homogeneous underfill encapsulant, which affects reliability, and how to avoid generating a void under the encapsulant, which also negatively affects reliability.
Adhesives are categorized either according to their physical form, chemical type, molecular structure, curing method, function, or application. Sometimes the same adhesive will be called by two or more different names, which makes sense when considering that adhesives essentially work as both structural and functional material in electronic packaging. That is they are barrier coats, and provide structural integrity, and provide electronic connections, and sometimes thermal dispersion.
Modelling is currently playing an important role in determining which adhesives to use in electronic packaging. This is because modeling techniques at the micro and macro scale aid greatly in determining the electrical, thermal, and mechanical performance of adhesives. Modelling may hold the key to using these polymers in the electronics manufacturing process with the least cost and the greatest output.