The Chronology of PT/35(b): 13 and 14 June 1990

13 and 14 June 1990

Williamson and Det Supt Gordon Ferrie (S4316D) took PT/35(b) to the World
Convention of the Printed Circuit Board Industry held at the SECC Glasgow on 13
and 14 June 90, the purpose being to allow experts in the field to examine the
fragment to further identification of the fragment. A room was set up there and
various individuals examined the fragment but nobody was able to provide any
information beyond what had already been established. (Note that one individual who
attended was Hans Brosamle of Siemens – see 27 April 1990, above.) According to
the officers’ HOLMES statements, a “point of variance” with the technical description
of the fragment (i.e. DP/141 the document prepared by Williamson based on
Worroll’s analysis) was noted by two men, Robert Linsdell (of Morton International
Dynachem, who had previously examined the fragment, see 9 March 1990, above)
and David Kingsley (of Graphic Electronics Group), both declaring the strong opinion
that the fragment was solder masked on one side only. According to Kingsley’s
HOLMES statement (S5578) he examined the fragment on 13 June using a desk
microscope and advised that he thought the fragment came from a low technology but
professionally made PCB. He then returned on 14 June, accompanied by Robert
Linsdell. He wished to re-examine the fragment as he disagreed with the description
in DP/141, and he was of the view that the fragment was only solder masked on the
side without the tracks. He was present when Linsdell also examined the fragment by
microscope and was of the same opinion. He then stated that the only means of
identifying the fragment would be through tracing the art work. In Linsdell’s ch10
CP he stated that he recalled viewing PT/35(b) at the convention in Glasgow but
could not remember why he had examined it there or if he noted anything new.

The precognoscer showed him DP/141 and Linsdell said he did not recall having seen this
report previously and he no longer felt able to comment on whether the report
accurately reflected his opinion about the fragment at the time. A PF’s note follows
which points out that DP/141 expressly says solder mask was applied to both sides of
the fragment, that Linsdell at precognition had remembered only solder mask on the
non-track side, yet he saw nothing wrong with the terms of DP/141.

Note that, according to Buwert’s statement S4649U, he arranged for Kingsley to sign
the label for PT/35(b) on 23 January 1992

NOTE The visit to the SECC marked the last of the examinations of the fragment
prior to the link being made to the MST-13 timer. In a memo from Williamson to the
SIO dated 6 September 1990 he lists the enquiries that had been carried out to identify
the fragment, including investigating various aspects of the board’s construction and it
also suggests that PCB circuit drawing manufacturers were consulted, as were clock
and timer manufacturers, to see what types of PCBs were installed in their products,
and also consulted were suppliers of electronic kits for “do it yourself” manufacturers.
There is then a list of 46 different companies that were either contacted or visited,
including all those mentioned in the summaries above plus various others which have
not been mentioned elsewhere. The memo states that after the fragment was
identified to the MST timer, many of the companies were re-contacted for advice on
the identification of the manufacturer.

Consideration of scientific examinations

A number of differences can be noted in the conclusions of the various experts. The
question of whether there was solder mask on one side or both is one area of
inconsistency, although given the comments made by Worroll in his Crown
precognition, in which he seems to backtrack from his original stance, it does seem
that the board was only solder masked on the side that did not have the tracking. (See
also the examination by Dr Reeves in 1999, below and chapter 8 of the statement of
reasons). A second area of inconsistency is regarding whether the board from which
PT/35(b) originated was single or double sided i.e. whether the board had tracking on
one side or both. According to Wheadon and Boyle at New England Laminates, they
were not sure whether it was double-sided although in his CP Wheadon did think it
was double-sided because that was normal and because of the solder mask present on
the non-track side of the fragment. Linsdell and Rawlings at Morton International
were of the view that it was double sided, as there was evidence of copper having
been scraped away on the side opposite the “1”. Worroll at Ferranti concluded that it
was single sided as there was no evidence of “through hole plating”, but in his ch10
CP he stated that his belief was based on instinct, as there was no circuitry on the
reverse side of the fragment. (In fact the absence of through hole plating on the timer
circuit boards was because surface mount technology was used to fit out the boards,
which did not require through hole plating even if the board was double sided.
Surface mount technology was relatively advanced in 1985, when the timers were
built.)

DP/19

DP/19

The last area of inconsistency relates to the coating on the conducting tracks.
Wheadon and Boyle thought the tracks were coated in tin/lead (Wheadon said as
much in evidence when referring to the photos they had taken (DP/19)), but
Wilkinson’s (Strathclyde Uni) metallurgy report indicates that the tracks had only tin
and copper, which would indicate a pure tin coating for the copper tracks. She did
detect some lead on areas of the “1”, which might suggest solder had been applied
there. Johnson’s (Manchester Uni) report appears to indicate that he did find traces of
lead on the conducting tracks. Worroll’s account, which predates Johnson’s report
(although Worroll was present when Johnson carried out his analysis) refers to the
tracks as being coated in pure tin. As described above, according to Thuring it seems
the circuit tracks were tin coated, not tin and lead. Given that Dr Johnson’s view was
that, when comparing PT/35(b) to DP/347(a) – the control sample MST-13 timer
board – in 1992 (see under 5 March 92 below), there was nothing in the results to
suggest the two were not the same, this issue does not appear significant.

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