Thick film technology is a polymer bonding process used in the manufacture of a diverse range of electronic and optical products the world over. Thick Film technology is used in the manufacture of plasma displays, ceramic packaging, optical sensors, ceramic circuitry, electronic chip components, solar cells, microelectromechanical systems (MEMS) and hermetic packaging, amongst others. Thick Film technology is a process which renders several successive layers of components on top of each other, incorporating a bonding liquid (Thick Film thermally decomposing binder) in-between the layers to help bind them together. The amalgamation is then heated to bond the layered components together forming the finished component.
In this interview, AZoM spoke to Peter Ferraro from Empower Materials, a leading manufacturer of clean, thermally decomposable Thick Film Polymers to find out more about the process and where the future lies with QPAC 40 PPC leading the way.
How does the process of Thick Film Bonding work? And what is the typical composition of a thermally decomposable Thick Film Material?
Thick film materials are typically composed of metal or ceramic powders with a glass powder added, together with an organic vehicle consisting mainly of polymeric binder dissolved in a solvent. The glass powder helps to bond the metal or ceramic to a substrate during the firing process which removes the organic vehicle and sinters the inorganic powders together.
You mentioned that both Organic and Inorganic components form an integral part of a thermally decomposable thick film material, what is the purpose of the Organic component and what are the best compounds to use?
The organic component is designed to produce a paste with a viscosity that allows the thick-film material to be applied to a substrate, usually by a screen-printing process. Ideally, the organic component should be completely removed without any residue, such as carbon, during the firing process.
During the manufacturing process, what are the main hurdles to overcome when using thick film technology?
First of all, the viscosity of the paste should be such that good print definition is achieved when the paste is dried on the substrate before firing. This includes uniform thickness and area, and sharp edges. Secondly, a short firing process at a low temperature is required for manufacturing efficiency.
Organic residue and other contaminants are a major issue to overcome when using thermally decomposable thick film binding, what are the main implications of the residue left behind?
If trapped in the film, residue from the organic binder can cause bubbles and/or blisters after firing. In addition, the electrical or optical performance can be degraded.
More specifically, residual carbon and the resulting drop in the optical transmission of the glass in plasma displays and solar panels manufactured using the thick film process can be a common problem. What are the implications of this from the end users perspective? And how can this problem be avoided during manufacture?
For such applications, residual carbon can result in poor quality product, reducing yield, and increasing manufacturing cost.
What are the most commonly used thick film binder systems in the market today?
Ethyl cellulose has been the traditional thick film polymeric binder because of low cost and the ability to provide good viscosity characteristics. Lower carbon residue can be achieved by using acrylic systems but viscosity is hard to control. On the other hand, QPAC binder systems have burn-out efficiency as good, or better than, acrylic and can be formulated to provide the required viscosity characteristics.
More specifically, what is the QPAC 40 PPC system?
The QPAC 40 PPC system consists of a high molecular weight polypropylene carbonate polymer dissolved in a solvent that is suitable for screen-printing applications. Dispersant may be added if necessary.
How does QPAC 40 PPC compare to the standard thick film binding materials? And what are the main benefits of the system?
QPAC 40 PPC produces significantly lower residue after firing, providing improved thick-film product performance, and can be decomposed efficiently during short firing processes at relatively low temperatures.
The QPAC 40 PPC system decomposes at a lower temperature than the more traditional binding agents, what is the significance of this and how does enhance the process?
The low decomposition temperature of QPAC allows burn-out in air with minimal oxidation of metal powders (such as Cu or Ni), the use of glass powders with lower melting temperatures (providing a wider range of properties), and shorter cycle times during processing.
With the current demand for smaller, more powerful electronics, where does Thick Film Technology sit and how does the QPAC system differ from the competition?
The performance of QPAC is unmatched by any other binder system and its use is well established in a variety of electronic applications. Thick film technology continues to grow and it is expected that QPAC will gradually replace most of the traditional binder systems used today.
There have been some significant advancements in recent research and development within the thick film manufacturing industry, with this in mind, what is the significance of the QPAC 40 PPC system?
QPAC has been used for several years in thick film pastes that provide metallization to aluminium nitride substrates. It is an ideal binder system for Cu and Ni metallization and its benefits have been demonstrated in multilayer ceramic capacitors. Its use can be expected to grow in plasma displays and solar cells.
What is the future for thick film technology? And, where is Empower materials focusing?
Thick-film technology has a bright future as is evident by the healthy business performance of the leading manufacturers of thick-film pastes. Empower Materials is partnering with leaders in the industry to make available a binder system that will improve product performance and provide a competitive advantage.
About Peter Ferraro
Working for Empower Materials for 11 years as Director of Business Development. Responsible for commercializing QPAC® polyalkylene carbonates in technical markets worldwide. Earlier work experience involved focusing on new business development of emerging technologies in nanoparticles, energy and digital imaging.
Educational background includes undergraduate degree in Chemical Engineering Degree from Columbia University and masters degree in business from Lehigh University.
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