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Ceramic Printed Circuit Boards for Aerospace Applications
Posted on 23/02/2018

Introduction to Ceramics

Ceramics have been the traditional material not only for electrical applications for the past 100 years, but have also been especially useful for highly reliable electronic applications. For instance, in the 19th century, ceramics were the standards for isolators and light bulb sockets. Moreover, radio tubes, early pacemakers, and military electronics extensively used ceramics in the 1930s. Since then, manufacturing technology has enhanced the material class amazingly from plain materials through new mixtures and nanotechnology to the level of today’s technical ceramics.

Properties and Materials

Compared to the plain ceramic materials earlier, new technical ceramics have improved on their durability, inertness, and chemical characteristics. Even their physical properties have undergone a sea of change, for instance, they do not shatter as easily. In most application cases, specifically for applications in space, it is much more than a single reason for using ceramic as the appropriate material system. However, ceramic materials are only a category and not the technology or a specific chemistry. Ceramic is usually a large group of technical materials providing good opportunities for enabling advanced requirements.

The greatest advantage of ceramic materials is their thermal mechanical behavior. Among thermal characteristics is included the coefficient of expansion, thermal conductivity, thermal capacity, aging under the influence of thermal cycling, and the ability to withstand higher temperatures.

Individually, as well as combinations of the above characteristics, are of advantage to the electronic applications, especially for space. For instance, unlike polymers and epoxies, ceramic materials do not show decomposition, and their chemical bonding does not break down from heat and UV radiation as it happens with organics. Moreover, ceramics do not soak or absorb humidity in a significant scale, and do not outgas in the extreme vacuum of deep space.

Function

In comparison with FR type of PCBs, ceramic materials need structuring for electronic functionalities. This requires different technologies and use of other materials. For instance, PCBs made of ceramic and copper may use alumina or aluminum nitride covered by copper foils using epoxy adhesives, but this would not help in thermal applications. This and other restrictions have led to product solutions such as DBC or direct bonded copper, including comparable covering techniques for AlN, which is widely used for power chips such as IGBTs.

Aerospace Application

Aerospace applications usually do not have miniaturization as their main target, and use ceramic PCBs mainly as a base for power dominated technology. To benefit definitely from this group of materials, engineers and designers must understand the limits and restrictions these materials possess, and interact with necessary process conditions in combination with calculations and balancing of the pros and cons.

Some advantageous characteristics of ceramic materials for electronics in aerospace applications are:

  • Coefficient of thermal expansion CTE very close to silicon and far below that of most usual metals
  • Excellent electrical isolation (even in elevated temperatures and over lifetime)
  • Good thermal conductivity as an isolator (useful for heat spreading and distribution)
  • Stable dielectric properties and low losses at high frequencies
  • Chemical stability against many chemicals, moisture, solvents, and consumables
  • Very slow aging due to consistency of substance
  • Compatibility to noble metal paste sintering technology, resulting in highly reliable conductors
  • High processing temperatures, far removed from normal operating range
  • Thermal resistance, showing no classic melting, decomposition, or softening
  • Mechanical stiffness, allowing rigid carriers, hardness, and wear resistance for sensors working in vacuum, fluids, and in industrial pollution
  • Resistance to EUV, plasma and ion bombardment as well as practically no outgassing in high vacuum, ideal for sensors for EUV semiconductor equipment.

Conclusion

At PCB Global, we have the technology capabilities not only to fabricate ceramic PCB’s, but to also assist you with any design specifications you may have regarding the application, use and outcome of the purpose of your ceramic PCB. For any enquiries or if you would like to arrange a quote for your ceramic PCB, please don’t hesitate to contact us as sales@pcbglobal.com