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Back taper drills, back taper drills with cylindrical tips and spade type drills were the three types available in the past for drilling multilayer boards in the diameter range of 0·8 to 1·1 mm. With packaging developments, drilling of smaller diameters, such as 0·4 mm, became necessary and care had to be taken to avoid drill breakage. The effects of board thickness, drill diameter and feed on drill breakage are analysed, followed by discussion of parameters affecting drilling accuracy and drill run‐out. The paper then deals with the effect of drill design on drill breakage, resin smear, nailheading and hole wall roughness. Results obtained using one back taper reference drill and seven other different spade type drill designs are analysed.

The California Circuits Association has moved to the following new mailing address: CCA, 8855 Atlanta Avenue, 210 Huntington Beach, CA 92646. Telephone: (714) 536 3519.

The subject of the meeting on 20 June was ‘Numerically Controlled Routing’. Dave Dosier, of Paul Dosier Associates, explained how important it is to maximise programming and routing equipment. Former dusty, noisy fabrication rooms are now humming with NC equipment.

Today modern epoxy base materials for printed circuit board production are designed with properties which ensure high dimensional stability, resistance to chemical action, and increased glass transition temperature, in order to meet the stringent demands now encountered in electronics use. Polyfunctional epoxy resins and the appropriate hardener/accelerator compositions are in widespread, effective use in the design of superior laminates. The quality of the through‐hole plating for holes drilled in these improved materials will depend on various parameters, including those covered by three main complexes: base material, mechanical processing, and chemical processes used for treatment of the drilled hole. Special attention is paid in this paper to the resin recession phenomenon in terms of processing parameters.

The Electronic Industries Association (EIA) has announced the release of EIA‐364–71, Solder Wicking Test Procedure for Electrical Connectors/ Sockets (Wave Solder Technique), formerly Standards Proposal No. 2185‐A. The object of this test is to determine whether a connector can be wave soldered to a printed wiring board without sustaining damage caused by solder wicking onto the contact surfaces or other areas that might alter its operating characteristics.

The CCA is a non‐profit organisation composed of member companies within the state of California, aimed at providing an environment for information exchange between individuals involved in the printed circuit industry. Each branch holds monthly meetings on state‐of‐the‐art technology. Other benefits of CCA membership include: free admission to Nepcon technical sessions; educational and employment information; reduced fees for the annual fall symposium; and a monthly newsletter.

The Annual Fall Symposium took place on 11–12 November, 1985, at the Marriott‐LAX Hotel, Los Angeles, focusing on the theme: ‘PC Technology: Materials, Processes and Requirements for Entry to the '90s’.

New Officers for 1988/89 ‐ CCA administration for the coming two years will be in the hands of the following office‐bearers:

Insulated Metal Substrates (IMS) have been used in the automotive industry for a number of years. The popularity of this technology is due to the good thermal conductivity of the thin insulation material, which is more effective than convection cooling, and the high temperature performance of the adhesive used for under‐bonnet applications. This paper describes how IMS circuits can be designed and manufactured with two or more layers without using the traditional plating processes.

A one‐day Technical Symposium on Printed Circuits will be held at the Swan Diplomat Hotel at Streatley on Thames, Berkshire, on Thursday 29 March 1990.