THE INVESTIGATIONS
80 As a matter of policy, Pacesetter encourages the return of all explanted pacemakers for laboratory examination and analysis. In about April 1998, Pacesetter became aware of a Tempo Pacemaker exhibiting the problem that was later the subject of the Hazard Alert - that is, early battery depletion and a resulting "no output condition". By July 1999, Pacesetter had received ten such devices. A more comprehensive investigation was then launched. The investigation was undertaken by Dr Morris, who was at the relevant time employed as Manager-Product Analysis and Reliability by St Jude Medical Inc in Sylmar, California facility. Dr Morris reported to Dr Khosravi, Vice President, Quality Assurance. Dr Khosravi was closely involved in the investigation and reviewed the work of Dr Morris and others. Dr Morris gave evidence. Dr Khosravi did not.
81 It is clear from the evidence that the task of isolating the cause of the problem proved extremely difficult. A variety of inquiries were undertaken but initially yielded no results. For example, in an attempt to ascertain the cause of the problem, the titanium can of some of the affected Tempo Pacemakers was cut open, using a high speed rotary cutting device. When that was done, the Pacemakers generally recovered both output and telemetry. In February 2000, a method was developed to open the cans in a way that minimised the mechanical disturbance to the contents.
82 Following this development, Dr Morris used an optical microscope to detect a minute bridge that had formed between the terminals or solder pads in the flex circuit. The flex circuit is a flexible insulated printed circuit used to connect the battery to the hybrid. The terminals or solder pads are only 0.25 mm apart. According to Dr Morris, many of the bridges were on the underside of the flex circuit, making them extremely difficult to see. The difficulty was compounded by the fact that the bridge was often covered by a white residue.
83 As a result of reviewing data relating to the no output Tempo Pacemakers, Dr Morris observed that all had been manufactured at Sylmar before January 1999. In March 2000, an accelerated life test was conducted on Tempo Pacemakers manufactured after 1998. The test seemed to confirm that no device manufactured after 1998 exhibited the problem of early battery depletion.
84 Initial analysis of the bridges observed by Dr Morris suggested that they were dendrites. The fact that dendrites are extremely thin and delicate was said to explain why the fault generally disappeared when, earlier in the investigations, the Pacemaker can had been cut open. The electrical pathway had simply been severed by the mechanical vibration and shock. (The evidence did not address whether and, if so, how the vibration could lead to a depleted battery being recharged.)
85 The effect of the bridge was to create an extra conductive path (a "partial short circuit") between the internal electrical connections of the affected Tempo Pacemaker. In other words, a circuit was made across a bridge that was formed between the solder pads, the points at which the copper conductive lines are connected to the battery terminals. This constituted an alternate and shorter circuit than the ordinary electrical circuit of the battery from the negative terminal to the hybrid and then back to the positive terminal. A diagrammatic representation (not, of course, to scale) of this effect was provided by Dr Brydon, as follows:
86 Dr Morris and his staff proceeded on the basis that of the three requirements for dendritic growth - electrical bias, moisture and ionic contamination - the first two were necessarily present in the devices. That was because, as already explained, electrical bias necessarily exists in electronic circuitry and it is inevitable, despite all precautions, that a small quantity of moisture will be present in all devices. It followed that the focus of the investigation had to be directed to locating the source of the ionic contamination.
87 One study initially suggested that the failed devices had a thin network of tin on the flex circuits. This led to a hypothesis, recorded as a memorandum of 15 May 2000 prepared by Dr Khosravi, that the root cause of the premature battery depletion was the presence of tin contamination in the flex circuits. A report prepared by Hi-Rel Laboratories established that flex circuits manufactured after December 1998 had traces of tin. Accordingly, Dr Morris concluded that the presence of tin in the flex circuits could not be the source of ionic contamination.
88 After considering various theories, inquiries concentrated on the solder that had been used in the production line. Solder is a low melting point alloy, commonly a 70:30 ratio of lead (Pb) and tin (Sn), used to form an electrically conducting point between one metallic component of a circuit board and another. The investigators ascertained that the solder which Pacesetter used when it commenced manufacturing the Tempo Pacemakers at Sylmar was different from the solder that Telectronics had used. Moreover, Telectronics had never experienced the bridging problem that Pacesetter had encountered.
89 The solder used by Pacesetter during the period until late 1998 was IF 14 solder supplied in a yellow spool and manufactured by Interflux NV Belgium ("yellow spool solder"). Pacesetter commenced using IF 14 solder supplied in blue spools by Interflux USA ("blue spool solder") in about late 1998. According to Dr Morris, operators had quickly shown a preference for the blue spool solder because, unlike the yellow spool solder, it did not leave a white residue. Dr Morris, upon reviewing the records, formed the view that production operators had more or less stopped using the yellow spool solder when the blue spool solder became available. He also concluded that Tempo Pacemakers manufactured after the yellow spool solder had ceased to be used had not failed in consequence of dendritic growth.
90 Armed with these discoveries, Dr Morris telephoned Mr Bruneel, a principal of Interflux USA which supplied the blue spool solder to Pacesetter. Mr Bruneel had previously been a partner in a Belgian business, Interflux Solder NV, which had supplied the yellow spool solder to Pacesetter. Mr Bruneel told Dr Morris that the two solders had slightly different chemistry in that the blue spool solder did not produce the white crystalline residue characteristic of the yellow spool solder. Mr Bruneel also said in that conversation that neither solder should have caused dendritic growth because they were both non-ionic and the residue from the yellow spool solder was non-conductive.
91 On 26 May 2000, Dr Morris travelled to Dallas to meet with Mr Bruneel. Dr Morris took with him a number of flex circuits from failed Tempo Pacemakers on which dendritic growth had been found. Mr Bruneel inspected the flex circuits using a hand held microscope. He identified a substance on the flex circuit that he described both to Dr Morris and in his evidence as a "moist residue". Mr Bruneel gave evidence that although he did no scientific testing, he was "pretty sure", based on his twenty-five years' experience, that this was conventional flux residue. Conventional flux is a compilation of ionic chemicals used to remove contaminants, usually oxides, from metallic surfaces prior to or during soldering. Mr Bruneel thought that the moist residue was likely to be a halide, probably a chloride or fluoride. He said in evidence that a halide flux should not be used in the process of manufacture in conjunction with the solder.
92 Upon his return to Sylmar, Dr Morris compared flex circuits that had not exhibited dendritic growth with flex circuits that had. He observed that the "moist residue" was not present on those flex circuits which had not exhibited dendritic growth. That prompted him to initiate a search for anything in the manufacturing area that might contain conventional flux. That search ultimately turned up a de-soldering wick which contained conventional flux. A de-soldering wick is used to remove solder from a connection that has previously been made. In order to remove the solder, the joint is heated and the de-soldering wick placed against the joint. The liquid solder is then absorbed by the de-soldering wick and can be removed.
93 According to Dr Morris, it was a "comparatively rare occurrence" for a de-soldering wick to be used in the manufacturing process for Tempo Pacemakers. Operators in the manufacturing area would visually inspect each solder joint after it had been completed. If the operator formed the view that it was not an optimal joint, the solder was removed using the de-soldering wick and the joint was re-soldered. This procedure was not regarded as "rework" for the purposes of Pacesetter's internal record-keeping. In particular, the "Traveler", which is the record of work carried out in relation to each Tempo Pacemaker, did not include any record of re-soldering carried out in this fashion. (Mr Bannon challenged Dr Morris on his evidence that re-soldering was not recorded on the Traveler, but I accept his evidence.) Accordingly, Pacesetter had no record as to which of the Tempo Pacemakers had been de-soldered using a de-soldering wick.
94 Since the de-soldering wick contained conventional flux (which is an ionic contaminant), it became clear to Dr Morris that some of the flex circuits for the Tempo Pacemakers must have come in contact with an ionic contaminant. The question still remained, however, as to why the cleaning process, which was designed to remove contaminants, both ionic and non-ionic, from the surface of the joint, had not removed all traces of the conventional flux. The answer that Dr Morris arrived at (which he supported in his evidence) was that, where the yellow spool solder was used, it left a tenacious crystalline residue. In Dr Morris' view, the residue was both non-metallic and non-ionic and thus could not cause or contribute to dendritic growth. Accordingly, he concluded (as he explained in his evidence) that:
"if the solder joint was re-soldered, using the de-soldering wick, the crystalline residue from the yellow spool solder absorbed the flux from the wick. Despite swabbing the joint at the completion of the re-soldering process, the residue still retained some flux from the wick. This flux then provided the source of ionic contamination which allowed the dendritic growth to proceed".
This view of the "most probable root cause" of the "failures" was recorded by Dr Khosravi in a memorandum of 30 May 2000, as follows:
"'Active flux' residue from the solder-wick (cases of re-soldering) retained by fluxes of the crystallizing solder, forming significant ionic contaminants, that in the presence of very low levels of moisture (after vacuum bake) and voltage of 3.5 V are forming dendrites".
95 Dr Morris' ultimate conclusion was that dendritic growth would only occur in circumstances where the yellow spool solder had been used in conjunction with the de-soldering wick. Accordingly, Pacesetter informed the TGA in a letter of 7 June 2000 that
"the solder used from the time that manufacturing transferred from Telectronics in 1997 until late in 1998 for attaching the battery to the flex circuit is susceptible to dendritic growth if the solder operation required re-work. Analysis has identified that an ionic contaminant can be introduced during the re-soldering process, which can then act to promote dendritic growth".