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In this issue of the Journal we conclude our series of articles on National and International Committees for Printed Wiring by examining the work carried out by “Panel Z‐Printed Circuit Techniques and Materials” of the Radio and Electronic Components Manufacturers' Association. In the past five issues of the Journal we have covered, as far as we are aware, all of the committees concerned with printed circuits which are currently functioning. However, we have yet to hear from overseas readers who are associated with, or are members of committees dealing with printed circuits or allied techniques with a view to preparing an article on their behalf for publication in a new series to start sometime next year.

The high cost of copper combined with a world shortage has emphasised the need for economy in its many applications. The manufacture of printed circuits by the etched foil technique produces a wastage of 60–80% of the copper cladding of the boards and although recovery of the copper can be effected, the process is costly and time consuming to an extent that makes it impracticable for the printed circuit manufacturer. With the increasing use of additive processes for printed circuit manufacture and the consequent saving in copper wastage, the use of electroless copper plating has assumed even greater significance than for its application to through hole plating and the advantages gained by freedom from the current density problems associated with electroplating need no stressing.

In this series of articles on printed circuit troubleshooting, the author in this issue of the journal focuses his attention on the mechanical aspects of printed circuit board manufacture by examining the problems commonly encountered in guillotining, roller cutting, piercing and blanking, and milling and routing. This article is the fourth and last in this series by the author.

The Oxford Moat House was the venue for a Dinner Dance on Saturday 23rd March, organised by Mr John Russell of the ICT Council. This, the first, hopefully, of many such gatherings, was well supported with about 100 attending. Mr Russell intends to organise next year's social evening at the same venue.

In this series of articles on printed circuit troubleshooting, the author in this issue of the journal focuses his attention on photoresists. The problems that most commonly occur during lamination, film development, subsequent plating processes, coating consistency, resist exposure and development are detailed.

The author continues his series of articles on printed circuit troubleshooting in this issue of the Journal by examining screen printing techniques. The problems associated with alkali soluble, solvent soluble, solder and plating resists, as well as notation inks, are examined in some detail. Possible causes and suggested remedies are tabulated.

Close spacing of conductors, surface mounted components and a multiplicity of DIPs have rendered the use of heat sinks on the PC board surface more and more hazardous. Where exposure to extreme temperatures is likely, the bond of heat sinks to the board has failed in 8% of cases during a recent investigation. Using the techniques described in this paper, any company with a multilayer manufacturing capability can produce a printed circuit board with good thermal conductivity and expansion characteristics related to most component mounting devices.

THE earliest origins of the Trident may be said to lie as far back as 1944 when we made some preliminary studies of the ways in which the newly arrived turbojet engine could be exploited for civil use. Our first thoughts were that the high consumption of the early centrifugal engines would restrict their practical use to short and medium hauls, and we envisaged a three‐engined aircraft with tail booms and engines buried in the rear of a short fuselage somewhat on the lines of a scaled‐up Vampire, capable of carrying 20 passengers over stages up to 750 statute miles and operating from 3,500—4,000 ft. runways.

Under this heading are given each month the principal articles of aeronautical interest appearing in the current issues of the Journals of the leading Professional Societies and Institutions.

Specification by manufacturer's grade, restricts competition; company specifications proliferate test methods; both increase costs. BS.3888 was incompatible with foreign specifications. IEC Publication 249 promised internationally acceptable standards and led to the flexible approach to BS.4584 which allows for progressive additions to the range of test materials—now at seven—with a further seven in the foreseeable future.