Today, nearly sixty years after Dr Paul Eisler came up with his proposals for a "printed circuit" to replace the point-to-point wiring used to interconnect the various components making up an electronic product or system, the technology developed at Technograph – the company set up to exploit his ideas – remains the foundation of the modern PCB fabrication industry. Although other methods of producing printed circuit boards were investigated, it was Eisler's etched foil concept that prevailed.
But for both Eisler and Technograph, getting the printed circuit off the ground was to take some time. Not only had development work to be undertaken, but the electronics industry had to be persuaded to drop point-to-point wiring in favour of an interconnection medium that, although inherently more consistent and more reliable, was, at least initially, considerably more expensive. Not an easy task.
Eisler's development work too was far from straightforward. His basic idea involved printing the required circuit pattern on to copper foil bonded to an insulating substrate. The printing was to be undertaken using a special ink which, upon subsequent immersion of the printed substrate in an etching chemical, would act as an etch-resist. The unwanted copper would be etched away leaving behind the etch-resist-protected circuit pattern. The commercial non-availability of copper-foil-clad insulating materials was the first of many difficulties that had to be overcome.
The early days of the Technograph company and of printed circuit technology development are closely intertwined. Technograph has its origins in a London-based printing firm named Henderson & Spalding whose proprietor, Harold Vezey-Strong, had, in 1941, engaged Eisler to help develop a new process for printing music called "Technograph". When in due course Vezey-Strong came to hear of Eisler’s ideas for a printed circuit, he provided the necessary financial and practical backing and set Eisler to work to prove his theories in the basement of Henderson & Spalding's London office in Shaftesbury Avenue. By 1942 Eisler had produced the world's first radio with components interconnected by means of a printed circuit. In February 1943 the first application for a British patent was made in the names of Vezey-Strong and Eisler.
Henderson & Spalding continued with the development and production of PCBs before eventually relinquishing responsibility for these new activities to an associated company, Hermoplast, and thence to a newly formed company, Technograph Printed Circuits Ltd. The latter was incorporated in May 1950. Eisler played a major role in all three companies.
During, and immediately after, World War II efforts had been made to interest UK government departments in the etched foil process. Indeed, some interest was generated, but no business of any significance resulted and in November 1949 help was sought from the National Research Development Corporation (NRDC). Negotiations on this topic continued during the early 1950s and eventually, in March 1954, the first instalment of a significant NRDC loan was received, a condition of this arrangement being that both Eisler and Vezey-Strong assigned their interest in the patents to the company.
Patents, licences and the pursuit of infringement claims were to require considerable effort over the years. The original single British patent application eventually resulted in three granted patents and one of these, 639178, which the company saw as the basic patent, was to be the one on which it was to fight and win its infringement action in the House of Lords in 1971. By June 1953 Technograph had been granted 12 patents in the UK and six in the USA (where Technograph Printed Circuits Inc had been established in 1952, primarily to take care of licensing arrangements). The company had also been granted 10 patents in other countries and had no less than 58 other applications pending.
Around this time Technograph was involved in licensing negotiations with, among others, the Telegraph Condenser Company (TCC), and the eventual granting of a licence to this large, internationally operating company was to mark the beginning of a fruitful relationship.
TCC set up a printed circuit division at its premises in Acton, London, the intention being to produce, under licence, PCBs for the open market (rather than for its own consumption). But the market itself had to be developed, with potential users being persuaded to try the new means of interconnecting components. This was no easy task. Although PCBs' consistency enabled them to offer increased interconnection reliability, the electronic circuits of the day were not particularly complex and hand wiring was not regarded as a significantly troublesome operation. It was also cheaper. The cost of producing a hand wired unit was around half that of one based on a printed circuit board.
Another problem that had to be addressed was the commercial non-availability of copper-clad base material. A member of the BICC Group, TCC was financially strong and it was this company's "clout" that persuaded supplier companies to persist in efforts to come up with suitable copper-clad laminates even though, in the short term at least, the market was tiny and volumes negligible. First attempts at developing such materials have been described as "laughable". Copper foils of 0.005-inch and 0.010-inch thickness were being offered where the actual requirement was for foil 0.0015-inch thick. And when suitably thin foil was produced, the adhesives used to bond it to the insulating base were not capable of producing anything like the required peel strength. It took years for the problems to be truly overcome.
But overcome they were, and by the late 1950s printed circuits were able to offer both technical and price advantages over hand wiring. One of the earliest products in the UK to fully benefit from these advantages was the portable gramophone used to play the recently introduced 45 rpm discs. These record players were selling in substantial numbers and the single-valve amplifiers they incorporated were PCB based.
Television and radio manufacturers were also high volume users of single-sided PCBs made using the print-and-etch technique on predominantly paper phenolic copper-clad laminates. Double-sided boards were being produced but not yet incorporating plated-through holes (PTHs), although this technique was under investigation at this time.
However, in addition to consumer products, the electronics industry was also beginning to develop equipment such as electrically-operated accounting machines for the business sector. These "professional electronic" applications demanded double-sided PCBs, but it was not until the early 1960s that both Technograph and TCC became serious players in the business of PTH board manufacture, the techniques of which had been perfected in the United States during the late 1950s.
The setting up of Technograph Printed Circuits Inc in the USA in 1952 was an exercise aimed at extracting royalties from US companies making printed circuits using UK-based Technograph's patented etched foil process. The exercise was not a great success, with little in the way of royalties being collected. However, one American PCB manufacturer - Photocircuits - recognised that Technograph might indeed have a strong case for patent infringement and so it became a Technograph licensee. Since Photocircuits was a much larger organisation than Technograph and had far more resources, it undertook considerably more R&D projects than Technograph could accommodate, and since the agreement was of a cross-licensing nature, it was Technograph that was the principal beneficiary of the arrangement.
The mid-to-late 1950s was an eventful period for Technograph, although progress during this period would be best described as "up and down". The lowest point came in 1955 when the company faced, and of course subsequently overcame, "a financial crisis". The relationship with Eisler, who failed to secure re-election as a director at the 1957 AGM but who remained a significant shareholder, was "somewhat volatile".
Trading results improved in 1956 and in June of that year the company's subsidiary - Technograph Electronic Products Ltd - took on responsibility for manufacture and sales, leaving the main company to take care of licensing and overall management. By the autumn of '56, orders for 4-5 months' production related to defence and industrial products were on the books.
By January 1957 manufacturing operations had been moved from south-east London to Fleet, Hampshire.
During the 1950s the finest track and gaps being produced were one sixteenth of an inch (0.0625-in), massive by today's standards, but perfectly adequate for the vast majority of applications which, compared to modern circuitry, were relatively simple.
A major development for the company in 1963 was the merging of TCC's printed circuit division into Technograph's manufacturing subsidiary, the latter changing its name to Technograph & Telegraph Ltd (T&T).
The company, by now a very significant UK manufacturer of printed circuits, progressed through the 1960s extending its factory, adding plant, including electroless plating equipment, and winning significant orders. The business placed by one customer, ICT, was so significant that, working together, both T&T and its American "partner", Photocircuits, eventually found themselves unable to produce the volumes of multilayer and PTH boards required and ICT opted to set up its own in-house PCB production facilities.
Much time and effort was spent by Technograph during the 1960s on legal matters appertaining to the validity/infringement of its printed circuit technology patents. Writs were issued in 1962, but it was not until1971 that a House of Lords decision finally confirmed that the basic patent was indeed valid and that it had been infringed. Later that year the first of many claims for damages against firms infringing the patent was met. Subsequent receipts of this nature in the early 1970s served to bolster trading results and, in 1973, it was announced that the Crown was to pay the company £51,000 less tax for the use by its contractors of Technograph's patented technology.
In 1971 all manufacturing operations were transferred from Fleet to Bracknell, Berkshire.
The early 1970s saw an explosion in the number of UK printed circuit suppliers and, although Technograph - in effect the developer of the printed circuit as we know it today - no longer dominated the sector, it nevertheless remained a very significant player. By 1979, however, it was "under pressure" and the Group was sold to RHP (Ransome, Hoffman, Pollard).
Footnote: Paul Eisler arrived in Britain in 1936 from Vienna, his birthplace in 1907, as a refugee from Nazi persecution. His invention of the etched foil printed circuit, whilst being of enormous benefit to the world-wide electronics industry, brought him little personal financial return. He died in 1992, aged 85. His autobiography, "My life with the Printed Circuit", ISBN 0934223041, is published by Lehigh University Press.