Browsing by Subject "Soldering"

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Solder joint inspection using thermal transient characteristics
(1987) Schellhase, John Charles, 1962-; Not available
Every year millions of dollars are spent by the electronics industry to identify and correct problems with defective solder joints. This preliminary study uses the thermal cooling transient characteristics of solder joints that have been warmed by short laser pulses to evaluate the quality of solder joints. Thermal radiation time constants are used to classify lap type solder joints since time constants are less susceptible to variations in the surface conditions on the solder joints which can cause large variations in the amount of thermal radiation being emitted by a warmed solder joint. The proposed algorithm uses four sequential thermal radiation data points gathered by an infrared detector after the short laser pulse in a laser inspection system. The thermal radiation time constant estimates for the solder joints are computed from the thermal radiation data and then employed to develop a preliminary process control chart of the form that could be used to monitor the reliability of the soldering process and signal when problems cause this process to deviate from normal production. The thermal time constants and the associated theoretical thermal radiation time constants that would be obtained using other infrared detectors can be estimated by using a temperature vs. emissive power relationship for the infrared detector in the inspection system of interest. Process control charts for other infrared detector systems can also be approximated by using the theoretical thermal radiation time constants obtained for other infrared detector systems. The results from the process control charts using thermal radiation time constant estimates are encouraging and show great promise of identifying when the soldering process begins to degrade and producing solder joints with poor quality. Also, the preliminary data involving solder joint cross sectional area for the lap joints show that the use of time constants to determine the quality of solder joints is supported by a linear correlation between a solder joint's cross sectional area and its thermal radiation time constant
Thermal analysis of surface mounted chip components during reflow soldering using finite element analysis
(1988) Goh, Robert Teck Lee, 1956-; Masada, Glenn Y.
In surface mount technology, electronic components are soldered directly onto printed wiring boards without having to insert the component leads into the board. This arrangement results in higher functional density boards with improved performance. Surface mounted chip components have the problem that they tend to move during the reflow soldering process. To get an better understanding of the reflow process and the problem of chip movement during reflow, a thermal analysis of type 1206 chip resistors and capacitors was performed using the NASTRAN finite element program. The analysis provided temperature profiles in the models resulting from different kinds of heat inputs. Also, the sensitivity of the temperature profiles to several model parameters was studied. The study found that Infrared reflow soldering produces a temperature profile that is less likely to produce chip movement during reflow. The study also showed how the thermal behavior of electronic components during reflow can be predicted using finite element software
Thermal modelling of the infrared solder reflow process
(1992) Eftychiou, Marios A., 1964-; Bergman, T.L.
A numerical model has been developed to predict the transient thermal response of a typical card assembly during infrared solder reflow. The model solves the transient, two-dimensional, laminar, compressible, and variable-property Navier-Stokes and energy equations which are coupled with the two-dimensional conduction and differential diffuse-gray radiation exchange equations. To validate the model, algorithm predictions are compared with published benchmark solutions. A base case geometry and operating conditions are defined and parametric investigations of the reflow process are performed to determine the important transport mechanisms and quantify the sensitivity of the process to uncertainties in convective and radiative conditions. The response of a typical card under reflow conditions is also presented. Predictions show that, for the case considered here, radiation is the dominant mode of heat transfer. The mixed convection heat transfer rates, although smaller than the radiative heating rates, affect the soldering process