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Printed wiring of assessed quality
World Abstracts on Microelectronics and Reliability
Reproducible methods for the fabrication of microwave strip lines of high precision and reliability. W BRAUER,G. KIENEL and R. WECHSUNG. Solid St. Technol. p. 67 (December 1976). Improvements in fabrication techniques of microstrip circuits for the 10 GHz range are described. Ceramic, sapphire and quartz were investigated as substrate materials and new measuring methods were developed for the determination of the dielectric constant, using the circular resonator, the rectangular resonator and the capacitance measurement methods. For producing the chromium-gold metaUization, the cathode sputtering technique was optimized in such a way that the gold layers had an extremely high adhesive strength and an electrical conductivity which was only 10~o lower than that of the bulk material. Circuit delineation was produced by means of ion etching. Microwave test circuits are described by means of which the fabrication parameters and their variations can be exactly related to the parameters of the finished microstrips. Evaluation of component quality for military and space applications. L. LESAEC and D. TABET. Electl Commun. 51 (4) (1976). Rigorous quality evaluation is a prime requirement for all components considered for military and space applications. This includes checks to ensure high reliability, particularly for satellite components. The first step is to evaluate possible component suppliers for a given application. Next the component is evaluated and a selection made, after which component qualification is used to verify the selection. Finally, tests are made throughout the production cycle to ensure that the high quality is maintained. Laboratoire Central de T616communications, a French research center of ITT, maintains a specialist test facility for component evaluation, both for internal users and outside customers. A survey of accelerated ageing techniques for solderable substrates. M. L. ACKROYD. Proc. lnternepcon, p. 214 (Oct. 19-21, 1976). The strength and reliability of a soldered joint depends to a very large extent on the wetting properties (solderability) of the substrate. A wide variety of "solderable" coatings are available to the electronics engineer, and accelerated ageing procedures play an important role in the assessment of the relative solderability levels of these different coatings on various basis metals. In this paper, the above topics will be discussed, the results of steam ageing tests (primarily on tin and tin/lead coated copper wires) will be presented, specified accelerated ageing procedures will be reviewed and, finally, correlations between accelerated ageing and normal storage will be briefly mentioned. Printed wiring of assessed quality. DR. T. REYNOLDSON. Proc. Internepcon. p. 40 (Oct, 19-21, 1976). The specifica3. C I R C U I T
AND
SYSTEMS
RELIABILITY,
Sequential testing of components for system reliability. P. F. PRESTON. IEEE Trans. Reliab. R-25, (5) 314 (Dec. 1976). It is often desirable to construct s-confidence limits for system reliability on the basis of data obtained from 'passfail' tests on the components of the system. This paper presents a general method for sequentially testing the components that provides data from which these s-confidence limits can be easily derived. The method is applicable to any s-coherent system for which the reliability function is known. It is a generalization of a scheme given by Winterbottom and Verrall for systems composed of units arranged either in series or parallel. Testers are getting better at finding microprocessor flaws. ANDY SANTONI. Electronics p. 57 (Dec. 23, 1976). Hardware
113
tion, with sub-documents nearing completion, contains minimum requirements for the release of printed wiring boards of assessed quality. The document invokes Capability Approval and, as part of the BS 9000 specification system for electronic components, claims the following benefits: Application in both military and civil markets; Rationalisation of number and content of specification; Defined assessment of manufacturer's quality system; Defined assessment of products before release by initial approval and subsequent production testing to common procedures; An independent National Supervising Inspectorate acting for BSI; Customer quality assessment of manufacturer's products; No concessions; Qualified products list. One approval has already been granted; over 20 applications are being progressed.
Troubleshooting in the electroless copper process. FRANK E. S'rONE. Circuit World 3, (2) 14 (Jan. 1977). Electroless copper plating achieves one or more of the following objectives: 1. lnterconnection of two sides of the printed circuit board or multilayer interconnection in the case of multilayer boards. 2. Enabling holes to be electroplated and ultimately filled with solder, thereby firmly anchoring mounted components. 3. Providing a surface for further electroplating (semiadditive processing). 4. Producing a total circuit (as in fully-additive processing). The electroless copper coating itself must possess certain qualities, some of which become more important the thicker the coating required. For example, the primary requirement of thin deposits of electroless copper is that they should be suitably conductive to allow further electroplating. When electroless copper is used to avoid flash panel electroplating, thickness of 0.6--3.7 microns are usually employed. In these cases the electroless copper must be suitably dense to withstand the handling and cleaning steps associated with pattern application and must have sufficiently low internal stress that good adhesion to substrates is obtained. When electroless copper is used to produce the entire circuitry, it alone must meet the ultimate requirements of the circuitry namely resistance to thermal shock during component soldering, circuit conductivity, mechanical insertion of components, flexing of the circuit, etc. Hence the physical properties of the deposit become of paramount importance in totally additive circuitry. MAINTENANCE
AND
REDUNDANCY
and software faults in prototype systems are exposed quickly when designers troubleshoot with logic and microprocessor analyzers, which tenaciously monitor the signal activity on address and data buses.
Improving quality through behaviour modification. D. A. SPRAGUE, B. ZINN and g. KREITNER. Quality Prog. p. 22 (Dec. 1976). While appropriate planning and controls can enhance final quality of products and services, there remains the critical, yet elusive, factor of motivating the employee to do his job well. Various quality incentive schemes have been used to stimulate quality performance of employees. A number of descriptions and evaluations of these various techniques have been written. This article describes a successful quality improvement
Reproducible methods for the fabrication of microwave strip lines of high precision and reliability. W BRAUER,G. KIENEL and R. WECHSUNG. Solid St. Technol. p. 67 (December 1976). Improvements in fabrication techniques of microstrip circuits for the 10 GHz range are described. Ceramic, sapphire and quartz were investigated as substrate materials and new measuring methods were developed for the determination of the dielectric constant, using the circular resonator, the rectangular resonator and the capacitance measurement methods. For producing the chromium-gold metaUization, the cathode sputtering technique was optimized in such a way that the gold layers had an extremely high adhesive strength and an electrical conductivity which was only 10~o lower than that of the bulk material. Circuit delineation was produced by means of ion etching. Microwave test circuits are described by means of which the fabrication parameters and their variations can be exactly related to the parameters of the finished microstrips. Evaluation of component quality for military and space applications. L. LESAEC and D. TABET. Electl Commun. 51 (4) (1976). Rigorous quality evaluation is a prime requirement for all components considered for military and space applications. This includes checks to ensure high reliability, particularly for satellite components. The first step is to evaluate possible component suppliers for a given application. Next the component is evaluated and a selection made, after which component qualification is used to verify the selection. Finally, tests are made throughout the production cycle to ensure that the high quality is maintained. Laboratoire Central de T616communications, a French research center of ITT, maintains a specialist test facility for component evaluation, both for internal users and outside customers. A survey of accelerated ageing techniques for solderable substrates. M. L. ACKROYD. Proc. lnternepcon, p. 214 (Oct. 19-21, 1976). The strength and reliability of a soldered joint depends to a very large extent on the wetting properties (solderability) of the substrate. A wide variety of "solderable" coatings are available to the electronics engineer, and accelerated ageing procedures play an important role in the assessment of the relative solderability levels of these different coatings on various basis metals. In this paper, the above topics will be discussed, the results of steam ageing tests (primarily on tin and tin/lead coated copper wires) will be presented, specified accelerated ageing procedures will be reviewed and, finally, correlations between accelerated ageing and normal storage will be briefly mentioned. Printed wiring of assessed quality. DR. T. REYNOLDSON. Proc. Internepcon. p. 40 (Oct, 19-21, 1976). The specifica3. C I R C U I T
AND
SYSTEMS
RELIABILITY,
Sequential testing of components for system reliability. P. F. PRESTON. IEEE Trans. Reliab. R-25, (5) 314 (Dec. 1976). It is often desirable to construct s-confidence limits for system reliability on the basis of data obtained from 'passfail' tests on the components of the system. This paper presents a general method for sequentially testing the components that provides data from which these s-confidence limits can be easily derived. The method is applicable to any s-coherent system for which the reliability function is known. It is a generalization of a scheme given by Winterbottom and Verrall for systems composed of units arranged either in series or parallel. Testers are getting better at finding microprocessor flaws. ANDY SANTONI. Electronics p. 57 (Dec. 23, 1976). Hardware
113
tion, with sub-documents nearing completion, contains minimum requirements for the release of printed wiring boards of assessed quality. The document invokes Capability Approval and, as part of the BS 9000 specification system for electronic components, claims the following benefits: Application in both military and civil markets; Rationalisation of number and content of specification; Defined assessment of manufacturer's quality system; Defined assessment of products before release by initial approval and subsequent production testing to common procedures; An independent National Supervising Inspectorate acting for BSI; Customer quality assessment of manufacturer's products; No concessions; Qualified products list. One approval has already been granted; over 20 applications are being progressed.
Troubleshooting in the electroless copper process. FRANK E. S'rONE. Circuit World 3, (2) 14 (Jan. 1977). Electroless copper plating achieves one or more of the following objectives: 1. lnterconnection of two sides of the printed circuit board or multilayer interconnection in the case of multilayer boards. 2. Enabling holes to be electroplated and ultimately filled with solder, thereby firmly anchoring mounted components. 3. Providing a surface for further electroplating (semiadditive processing). 4. Producing a total circuit (as in fully-additive processing). The electroless copper coating itself must possess certain qualities, some of which become more important the thicker the coating required. For example, the primary requirement of thin deposits of electroless copper is that they should be suitably conductive to allow further electroplating. When electroless copper is used to avoid flash panel electroplating, thickness of 0.6--3.7 microns are usually employed. In these cases the electroless copper must be suitably dense to withstand the handling and cleaning steps associated with pattern application and must have sufficiently low internal stress that good adhesion to substrates is obtained. When electroless copper is used to produce the entire circuitry, it alone must meet the ultimate requirements of the circuitry namely resistance to thermal shock during component soldering, circuit conductivity, mechanical insertion of components, flexing of the circuit, etc. Hence the physical properties of the deposit become of paramount importance in totally additive circuitry. MAINTENANCE
AND
REDUNDANCY
and software faults in prototype systems are exposed quickly when designers troubleshoot with logic and microprocessor analyzers, which tenaciously monitor the signal activity on address and data buses.
Improving quality through behaviour modification. D. A. SPRAGUE, B. ZINN and g. KREITNER. Quality Prog. p. 22 (Dec. 1976). While appropriate planning and controls can enhance final quality of products and services, there remains the critical, yet elusive, factor of motivating the employee to do his job well. Various quality incentive schemes have been used to stimulate quality performance of employees. A number of descriptions and evaluations of these various techniques have been written. This article describes a successful quality improvement