BGA assembly is key to tagging fish

LONDON — CIL, the Andover-based electronics design and manufacturing company, has worked with the scientific research and advisory centre Cefas (the Centre for Environment Fisheries and Aquaculture Science) to manufacture a data storage tag (DST) for fish that uses the latest double-sided ball grid array technology to set new standards for this type of recording device.

Tagging fish provides unparalleled insights into how these creatures behave and respond to different environments. This allows a better understanding of the biology of commercial fish and helps to assess how different management options, such as closing an area of a fishery, may help to sustain endangered fish stocks.

To ensure that the normal behaviour of the tagged fish is not disrupted, the size of the tag is critical. The G5 is 8mm in diameter, 30mm long and weighs 1 gram in water. This reduced size allows tagging studies to be carried out on a wider range of species and is likely to open up new fields of research.

Earlier versions of Cefas tags have been used on cod, plaice and rays in the North Sea, the Irish Sea and the English Channel and on penguins, albatross, tuna, elephant seals and sea turtles worldwide including in Japan, America, the Falkland Islands and Australia.

The latest tag stores records of pressure, which is translated to depth and temperature. When a tagged fish is caught a reward is paid to the fishermen for the return of the tag and the data stored is downloaded for analysis on Cefas-developed software systems.

Seas around the UK are generally well mapped for depth, tidal range and temperature and so from the information recorded on these tags it is possible to determine the scale and seasonal patterns of fish movements.

The Cefas G5, the result of 20 years of research and development, has more memory and increased capability than existing tags. When designing the tag, engineers at Cefas were aware that, because of the required power for unit size, the latest electronics manufacturing techniques would have to be used if the product was going to be a commercial success.

CIL was contacted and worked in close collaboration with Cefas to produce a design that could package the sophisticated electronic circuitry into a circuit board measuring 19mm x 6.88mm, with the larger parts being central to the PCB as it fits inside a tube. Using the PADS PCB computer-aided design program the resultant design incorporates innovative double-sided BGA assembly techniques combined with the very latest surface mount placement equipment provided by MIRAE machines. To ensure that the device achieved commercially viable production yields, the latest flying probe and X-ray testing techniques were also used.

Another area that was crucial for success was the need to achieve extremely low quiescent currents of 2-3 micro amps to ensure a longer operational life. It was necessary to investigate new soldering and cleaning methods in order to reduce flux leakage paths to a minimum. CIL uses ALPHA METAL’s soldering systems and a complementary cleaning system throughout the assembly process thus enabling the tags to be manufactured to the cleanliness standard required to achieve the low quiescent currents that were vital to the project.

CIL produced a viable, proven unit within eight weeks of the initial meeting and production quantities four weeks after that. John Boston, managing director of CIL, said, “We were charged with designing a lot of technology in a small space and I honestly think no other company could have offered this range of service or carried out all aspects of the whole job. This project took us into new areas of technology and we are continuing to build up our expertise in the use of new soldering and cleaning techniques to achieve minimum quiescent currents.”

Mike Challiss, manager of the Electronic Design team at Cefas, said, “CIL has worked hard to design a PCB layout that met our demanding size constraints while maintaining high production yields.”

Developed by the Cefas Applied Technology team, in close conjunction with fisheries scientists, the G5 tag is capable of taking one million readings over a one-year battery life. It has independent pressure and temperature settings that provide users with increased programming flexibility.

Cefas is an executive agency of Defra (Department for Environment, Food and Rural Affairs) and much of its work is carried out for the UK government and the European Union where its research and advice is utilised by policy-makers. It has a staff of approximately 550 who are based at three specialist laboratories within the UK. Facilities include the latest laboratory, tank and aquatic field-based equipment and an ocean-going research vessel.

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