Advances in Electronic Circuit Packaging : Volume 5 Proceedings of the Fifth International Electronic Circuit Packaging Symposium sponsored by the University of Colorado, EDN (Electrical Design News), and Design News, held at Boulder, Colorado, August 19-

Many types and classes of embedding compounds are available for encapsulating electronic packages. For a particular application, an embedding compound must be selected that meets the design parameters, the electrical, mechanical, thermal, and environmental requirements. The factual property data necessary for such selection and the comparative advantages and disadvantages of the available encapsulating and potting compounds are tabulated and discussed. The problern of selecting a specific encapsulant for a particular electronic package currently being used in an aerospace application is presented. The matehing of the design parameter, the electrical, mechanical, thermal, and environmental requirements to the electrical, physical, and thermal properties of the available embedding materials is described. ## INTRODUCI'ION MANY TYPES OF EPOXY, silicone, and polyurethane casting, coating, and foam-in-place materials are available for the protective encapsulation of electronic circuits. Little information is available on the comparative advantages and disadvantages of these encapsulants for electronic circuit packaging. Which encapsulating material to use for a particular electronic device is a problern facing many electronic packaging engineers. Technical property data on encapsulants are widely scattered among vendor's literature, military specifications, company specifications, technical journals, and technical reports by the various users of these materials. It is the intent of this paper to tabulate and classify the technical property data and the comparative advantages and disadvantages of the available encapsulating materials and to show how this information was used in the selection of an encapsulant for the environmental protection of a particular electronic package. ## SELECfiON OF ENCAPSULANT In most electronic packaging applications the encapsulant has the triple function of a structural member, electrical insulator, and heat-conducting medium, and must maintain these properties through many adverse environments. The selection of encapsulants to perform these important functions is an important part of electronic packaging. Encapsulants should be selected on the basis of a detailed technical analysis of the electrical, mechanical, thermal, and environmental requirements. The technical analysis should be conducted, and the encapsulant selected, during the initial stages of the packaging design. The actual Iayout of the package should be begun with the electrical, mechanical, thermal, and physical properties of the selected encapsulant firmly in mind. Since the electrical, mechanical, thermal, and physical properties of the encapsulants are all temperature dependent, a detailed thermal analysis of the circuit is especially important. The results of this thermal calculation or measurement will determine whether highly filled 1012-1014 350 4.0-5.0 12 X 10 3 3-4 X 10 3 25 7-10 X 10 3 1 x 10• 4 x w-• 90-too x w-• 100 max Disadvantages Poor electricals (above 75'C) Poor mechanicals (above 75'C) High coefficient of expansion Front Matter....Pages i-vi Encapsulants for Electronic Packaging....Pages 1-12 Use of Radiation-Cross-Linked Materials for Encapsulating and Terminating Devices....Pages 13-20 Encapsulating with Loose Microballoons....Pages 21-27 Packaging Concept for a Miniature Low-Light-Level TV Camera....Pages 28-42 The Heat-Sink Module....Pages 43-57 Producibility Norms for Electronic System Packaging....Pages 58-62 Development of Packaging Techniques for a 960-Bit Plated-Wire Memory....Pages 63-71 Packaging Computer Circuitry for Space Applications—A Two-Part Compendium....Pages 72-86 A Cost and Performance Analysis of Encapsulation by Transfer Molding....Pages 87-97 Packaging of Miniature Diode Assemblies....Pages 98-105 Transfer Molding of Silicone Compounds for Environmental Protection of Electronic Modular Systems....Pages 106-118 A Feasibility Study in Miniaturized Packaging....Pages 119-132 Interconnection and Organization of Functional Electronic Blocks....Pages 133-140 Designing for Multilayer Circuits....Pages 141-156 A Flexible Module Concept for Electronic Box Design....Pages 157-164 A High-Frequency Multiple-Signal-Conductor Transmission Line....Pages 165-177 High-Frequency Interconnections....Pages 178-187 Interconnection System....Pages 188-200 Substitution of a Printed Conductor Ring Harness for a Conventional Cable Harness on the Mariner Series Spacecraft....Pages 201-213 Design of Connectors for Electronic Packaging....Pages 214-225 Mechanical and Electronic Packaging for a Launch-Vehicle Guidance Computer....Pages 226-241 Standard Package for Microcircuits....Pages 242-248 Semiconductor Circuits and Modular Packaging....Pages 249-265 A Packaging Evaluation of a Five-Bit Adder....Pages 266-277 Radiation Effects in Epoxies Used as Encapsulants for Electronic Packages....Pages 278-283 Designing a High-Voltage Power Supply for a Space Radar System....Pages 284-297