PRINTED CIRCUIT BOARD TECHNOLOGIES FOR THE REALIZATION OF STRETCHABLE ELECTRONIC SYSTEMS

摘要

In an increasing number of novel electronic applicationsrnthe ability of an electronic system to comply with arncertain degree of elongation is requested. Suchrnelongations may either be a single stretching during thernfabrication process, or the system may be subjected tornrepeated stretch and release cycles. Different technicalrnapproaches to add elasticity to electronic circuitries havernbeen developed and investigated during recent years. Inrnthe present paper a short overview of these technologiesrnwill be given. One particular technology will be treated inrnmore detail, which makes use of conventional fabricationrntechnologies for printed circuit boards. The nonconventionalrnbuilding blocks of the realized stretchablerncircuit boards are (i) the stretchable matrix material,rnthermoplastic polyurethane, and (ii) meandering copperrnconductors between electronic components. With minorrnsupport measures such boards can be handled and treatedrnlike rigid printed circuit boards throughout the fabricationrnprocess. For component assembly onto the stretchablerncircuits again conventional process technology applies:rnsolder printing, pick and place, reflow. The onlyrnconstraint -due to the physical properties of the stretchablernmatrix- is the use of a low temperature solder alloy likernSnBi and the respectively low reflow temperature. Afterrnassembly the components are usually encapsulated withrnpolyurethane. So far a number of stretchable electronicrnapplications have been realized. The examples which willrnbe presented in the present paper are a band aid withrnembedded sensors and a control unit and the integration ofrnstretchable systems into textiles