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MICRO IN GERMANY | FOCUS Innovative Micro Electronics Used in the Fight Against Cancer A WORLD FIRST: << Figure 1 >>

CZT pixel detectors for measuring proton beams in the course of a new kind of proton therapy

In central Dresden, behind six-meter thick concrete walls, the first instrument of its kind to be used in the fight against cancer is built. The equipment weighs a total of 700 metric tons and is designed for a new kind of proton therapy. It consists primarily of a particle accelerator (cyclotron), a radiation detector and a moving gantry, allowing the patient to be irradiated from different angles. The team at the “National Center for Radiation Research in Oncology” (OncoRay) accelerates protons in the particle accelerator to two- thirds the speed of light and uses them to destroy the genetic material of the cancer cells, thereby preventing the tumour spreading.

Research scientists and doctors will start arriving at the OncoRay centre in 2014, when the first patients will also be treated. In a world first, they will be testing a unique technology, which accelerates protons using high-energy laser beams instead of electromagnetic fields. This refinement considerably reduces the technical efforts required for proton therapy, resulting in big cost savings. Irradiation with protons is much less invasive than conventional treatment with ultra-hard X-rays. Unlike photons, protons only destroy the cell tissue of the tumour, leaving the tissue in the projection angle and behind the cancer cells unaffected.

The Compton camera used in proton therapy acts as a radiation detector and one version consists of 80 to 160 smaller pixel detectors. The pixel detectors constantly measure the radiation and provide feedback to precisely control the proton beams. Measuring 20x20 mm, a pixel detector has 8x8 pixels and uses cadmium zinc telluride (CZT). CZT has some important advantages as a detector material: CZT is an intrinsic II-VI semiconductor, so there is no need to alter the electrical conductivity of the original material by introducing dopant atoms. However, the ionic bonding of the material is liable to defects in the crystal lattice, making it particularly brittle and difficult to handle. The weight of the chips is relatively high at 12 g, making things even more difficult for the processing technology.

Cicor Advanced Microelectronics & Substrates (AMS), as one of two Cicor Group Divisions, took up the challenge of the assembly for the highly sophisticated CZT pixel detectors on the flexible substrates. For the production of the pixel detectors new assembly tools were designed and individual contact techniques of conductive gluing were developed for the highly sensitive sensors. This enables to overcome the difficulties associated with the material CZT. Furthermore, Cicor AMS accepts the chip assembly of the CZT sensor chips and bonded them on flexible printed circuit boards with 64 connections. The strip detector as a modification of the pixel detector is based on the same function principle and detects the high-energy radiation via long electrode strips instead of the small pixels.

Apart from pixel detectors, Cicor AMS is successful in other areas of medical technology. Examples include medical instruments for nerve monitoring and eye and apnea implants. Based on flexible and rigid substrates, these products reflect the broad range of technologies offered by Cicor AMS: substrate processing (ceramic, polyimide, LCP, LTCC, flexible, rigid and rigid-flex PCB etc.), reel- to-reel manufacturing, micro assembly (down to SMD 01005), packaging, design, screening and tests. Cicor AMS is a full-service provider, providing detailed advice to its demanding customers at every stage of development and executing very small to high volume production.

<< Figure 2: CZT pixel

detector on

flexible circuit board. >>

The Cicor Group offers comprehensive outsourcing services and sound advice for applications in medical technology. As a complete solution provider, the group develops together with its customers and partners innovative products and solutions that meet the needs of the market and the latest trends and are con- vincing in their application. The broad portfolio of innovative technologies, services and global manufacturing capabilities provides the right solution for highest requirements such as high- tech and high-reliability applications.

Cicor AMS

8| commercial micro manufacturing international Vol 7 No.3

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