Development of a two-color fiber optic measurement system for manufacturing process control

ABSTRACT Bonding is a critical process often employed in the manufacture of electronic components. The temperatures associated with the bonding process affect the quality and performance of a final product. This temperature can be observed using a two-color fiber-optic measurement system which monitors temperatures during the manufacturing process by gathering and analyzing infrared radiation emitted from a target device. The system described in this document is intended for use in process control of component fabrication; however, it is applicable to a variety of fields both within and beyond the realm of manufacturing. This is verified by way of post-design experimentation involving solar sail material used commonly in aerospace construction. Keywords: Infrared, Process Control, Fiber-Optic, Two-Color Detection, Spectral Emittance, Graybody 1. INTRODUCTION A key process associated with in the manufacture of electronic components is bonding. Bonding involves the permanent fusion of two or more metallic elements by applying heat and pressure to the desired junction. An electric current is delivered across a bonder tip and simultaneously placed in contact with the metallic surfaces, subsequently creating a permanent metallic bond. This common manufacturing process is critical to the development of electronic equipment. If materials are poorly bonded, any signal carried across the bond may be distorted or attenuated. A poorly joined surface could be the result of impurities present within the fused surfaces. Additionally, if an appropriate temperature is not maintained at the bonder tip during the fusing process, the joint produced may not be reliable. Initialization and control of the temperature, pressure, and duration of the process can minimize the occurrence of poorly produced joints. The process of bonding, as it relates to the manufacture of electronics, does not typically involve real-time monitoring of properties such as temperature and pressure. Such feedback is rarely received from the device or the material involved, and any indication of inadequate characteristics arrives through the manufacture of defective components. Yet these properties, at the bonding point, have an enormous effect on the quality of the bond. The ability to monitor and analyze properties such as temperature and pressure allows for direct control over the finished product. There are numerous methods by which to obtain a temperature measurement from a target source such as a bonder tip. Most methods involve devices that must maintain prolonged contact with the target. A common laboratory example of such a device is a thermocouple, which is a convenient and commonly used thermal measurement device. The use of a thermocouple to provide temperature measurements from a target would involve a relatively simple system. The resulting system, however, would have a number of critical drawbacks. A contact measurement device such as a thermocouple acts inherently like a heat sink, drawing thermal energy away from a target, which may alter its temperature profile. Attachment of the thermocouple to the target would also necessitate the creation of a permanent bond. The process of creating this permanent bond through a technique such as welding would be time consuming and inconvenient in a manufacturing environment. Moreover, the bond would likely have an adverse affect on the thermal properties of the target. These effects may in turn reduce both the life and the performance of the target unde r study. A final drawback with regard to contact measurement devices is the time delay involved in signal acquisition. A Correspondence: email kosturzr@jmu.edu ; Telephone 540.432.3330