Design and Implementation of an Infrared Radiant Source for Humidity Testing

A novel way to measure humidity through testing the emissivity of an area radiant source is presented in this paper. The method can be applied in the environment at near room temperature (5~95 °C) across the relative humidity (RH) range of 20~90% RH. The source, with a grooved radiant surface, works in the far infrared wavelength band of 8~12 μm. The Monte-Carlo model for thermal radiation was set up to analyze the V-grooved radiant surface. Heat pipe technology is used to maintain an isothermal radiant surface. The fuzzy-PID control method was adopted to solve the problems of intense heat inertia and being easily interfered by the environment. This enabled the system to be used robustly across a large temperature range with high precision. The experimental results tested with a scanning radiant thermometer showed that the radiant source can provide a uniform thermal radiation capable of satisfying the requirements of humidity testing. The calibration method for the radiant source for humidity was explored, which is available for testing humidity.

Doubts on Kissinger´s method of kinetic evaluation based on several conceptual models showing the difference between the maximum of reaction rate and the extreme of a DTA peak

The famous Kissinger's kinetic evaluation method (Anal. Chem. 1957) is examined with respect to the feasible impact of the individual quantities and assumptions involved, namely the model of reaction mechanism, f(a) (with the iso- and nonisothermal degrees of conversion, ? and ?) the rate constant, k(T) (and associated activation energy, E), heating/cooling rate, b (supplementing additional thermodynamic term for the melt undercooling, ?T) and above all, the association of the characteristic temperature, Tm, with the DTA peak apex. It is shown that the Kissinger/s equation, in contrary to the results of Vold (Anal. Chem. 1949), is omitting the term of heat inertia arising from the true balance of heat fluxes. The absence of this term skews the evaluated values of activation energies.

A Novel Projection Moire´ System for Measuring PWBA Warpage During Simulated Optimized Convective Reflow Process

The shadow moire´ technique is a widely used method of measuring printed wiring board (PWB) warpage. It has a high resolution, high accuracy and is suitable for use in an online environment. A shortcoming of the shadow moire´ technique is that it cannot be used to measure PWBs populated with chip packages. In this paper, a novel warpage measurement system based on the projection moire´ technique is presented. The system can be used to measure bare PWBs as well as PWBs populated with chip packages. In order to use the projection moire´ system to accurately determine the warpage of PWBs and chip packages separately, an automated chip package detection algorithm based on active contours is utilized. Unlike the shadow moire´ technique which uses a glass grating, the projection moire´ technique uses a virtual grating. The virtual grating sizes can be adjusted, making it versatile for measuring various PWB and chip package sizes. Without the glass grating, which is a substantial heat inertia, the PWB/PWBA/chip package sample can be heated more evenly during the thermal process. The projection moire´ system described in this paper can also be used to measure PWB/PWBA/chip package warpage during convective reflow processes. In this paper, the characteristics of the projection moire´ warpage measurement system will be described. In addition, the system will be used to measure the warpage of a PWB and plastic ball grid array (PBGA) packages during a Lee optimized convective reflow process. It is concluded that this projection moire´ warpage measurement system is a powerful tool to study the warpage of populated PWBs during convective reflow processes.