Electronics packaging materials suppliers traditionally have functioned as developers of continuously evolving formulations that enhance both component and assembly performance and reliability. Applications such as encapsulating, bonding, stress relief, heat dissipation and others have led to the development of packaging materials offering improved thermal stability, better moisture protection, greater adhesion, lower modulus, higher strength and even controlled electrical conductivity. As OEMs seek to keep pace with changing markets, process efficiency also has taken its place among fundamental performance criteria.
In recent years, several trends have contributed to changes in the materials supplier's role. Traditionally, semiconductor OEMs had resources of their own for developing materials and processes. However, changing economics have led to downsizing within many firms, leaving manufacturers with fewer resources. In Asia, many Japanese semiconductor plants are relocating outside the country, and the attendant geographic shift of production and design engineers creates a gap in materials engineering support. Additionally, Taiwanese companies have increased their capabilities greatly, leading many engineers once employed in other countries (especially the United States) to seek positions in Taiwan. All these factors have forced OEMs to prioritize their dwindling resources, with more responsibility shifting toward materials and equipment suppliers.
Amidst these changes, developing technology continues to deliver components offering higher speeds and greater power densities than ever before, and architectures continue to shrink. As such, rising temperature has become a key hurdle facing designers. This presents two primary issues: 1) how to design more heat-resistant packages, and 2) how to remove as much heat as possible from specific components or assemblies.
Initially, materials suppliers approached the problem with off-the-shelf formulations to serve a range of applications. But the number and interaction of the variables involved now requires that OEMs take their cooperation with materials and equipment suppliers to a new level. With the escalating thermal requirements of next-generation designs, every interface becomes an issue, and it seems clear that only a total-solution approach will allow true thermal efficiency to be designed into packages.
To reduce interfacial resistance and optimize heat dissipation, manufacturers and suppliers have begun reviewing the entire package and recognizing not only the roles played by the package's individual parts, but also how their interaction affects thermal transfer. Materials engineers now work with package designers to evaluate heat spreader coatings, chip passivation, thermal interface materials and other functions of thermal materials.
From this new approach, a new generation of thermal interface materials has begun to emerge. These include advanced phase-change materials that offer the thermal conductivity of greases and the application ease of pads, without the run-off problems experienced in many grease formulations.
New Requirements, More Teamwork
As the standard product line gives way to custom compounds, packaging materials no longer are an off-the-shelf selection based on thermal performance, electrical performance or reliability targets. Suppliers are finding that they can more cost-effectively develop individual formulations that offer a specific mix of physical properties when they more fully understand customer needs by being involved in the ongoing design process. As a result, both suppliers and manufacturers can eliminate the costly and time-consuming process of trial and error.
Like physical properties, processing characteristics also can be manipulated to best suit an individual manufacturing operation if all the key suppliers are involved from a design's initial stages. Package designers can explore the ramifications of pads vs. dispensed liquids without doing actual product trials.
The current trend toward shorter product life cycles has shifted the focus of many OEMs away from long-term reliability, driving many to concentrate more on performance and cost. As companies continue their drive for cost reductions and outsourcing becomes an accepted fact of life, key functions in R&D, testing, process evaluation and other areas are likely to become the responsibility of the materials supplier. Given the complexity of the total solution, however, success depends on increasing cooperation levels between all the key partners involved.
Tom Cook, executive director, may be contacted at Dow Corning Corp., 2200 W. Salzburg Rd., Midland, MI 48686-0994; (989) 496-4400; E-mail: [email protected]