VASCA logo

In the early days of semiconductor manufacture, before the existence of pro-Electron, which was founded in 1966, there was a British association of semiconductor manufacturers called VASCA. This stands for "The Electronic Valve and Semiconductor Manufacturers' Association". The use of the word "valve" ("tube" in the USA) is a clue that this organisation pre-dates semiconductors, however I do not know its origins, so If you have information about it, please

VASCA does not seem to have been a happy organisation, and it ultimately failed because it was limited to UK manufacturers. However it did publish a couple of important early standards documents.


VASCA booklet

This booklet is the "Record of Semiconductor Outlines", first published in May 1962; the second edition shown is dated exactly one year later. It contains outline and base drawings for semiconductors manufactured by VASCA members. At the time of the second edition the member list was

  • AEI Ltd
  • Brush Crystal Co Ltd
  • Ferranti Ltd
  • General Electric Co Ltd
  • Hughes International (UK) Ltd
  • International Rectifier Co (GB) Ltd
  • Joseph Lucas (Electrical) Ltd
  • Mullard Ltd
  • Newmarket Transistors Ltd
  • Semiconductors Ltd
  • Standard Telephones & Cables Ltd
  • Texas Instruments Ltd
  • Westinghouse Brake & Signal Co Ltd

The booklet employs three types of symbolic names:

  • The letters SO indicate Semiconductor Device Outline and are followed by a hyphen and a serial number.
  • The letters SB indicate Semiconductor Device Base and are followed by a figure indicating the number of leads and then a hyphen and a serial number.
  • The letters SG indicate Semiconductor Device Gauge and are followed by a hyphen and a serial number.

Only the first of these is commonly encountered, and even that is now unusual and only applies to long-obsolete devices.


SO-2 outline

Undoubtedly the most significant of the VASCA outlines is the SO-2, which was used by the famous Philips/Mullard/Valvo 'black glass' germanium transistors such as OC71, and also by the higher power types such as OC72 that employed an aluminium sleeve over the glass body.

The SO-2 specification is very flexible: it allows for the presence of a wider body section at the base end, and the body length can vary from .32 inches to .62 inches, nearly doubling. Other manufacturers used variations of it, for example Texas Instruments Ltd low-power devices employed a metal version.

The table at the bottom of the page shows "cross references" to specifications from other standards bodies, including JEDEC 'TO-' outlines. However the SO-2 outline has no JEDEC cross-reference. Other types do have, for example

  • SO-4 is equivalent to TO-22
  • SO-5 is equivalent to TO-3
  • SO-21 is equivalent to TO-1
  • SO-23 is equivalent to TO-7

SO-16 outline

The SO outlines also include diodes, unlike JEDEC / pro-Electron which named transistors TO- and diodes DO-. The image shows the SO-16 which is stated to cross-reference to DO-1, DO-2 and DO-3. Its specifications are sufficiently broad to encompass all three.






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