Thermo mechanical analysis of through-hole solder joint using strain partitioning method

Currently in the electronics industry there is a desire to increase component reliability. Fatigue failure in solder joints is an important design consideration for electronic packaging. In through-hole components, fatigue failure of leads has been observed to antecede fatigue failure of solder joints. The main objective of the study for a solder joint in a plated-through-hole bearing the pin during the temperature cycle was to ascertain the thermo mechanical behavior and the dominant deformation mode. The Digital Speckle Correlation (DSC) technique, which is a computer vision technique, was applied for the measurement of solder joint deforamtion for a prescribed outlined temperature and time. The dimensions for the area of the solder joint under study were 21 by 21 um, located at the centre of the hole. And computation of averaged shear strains at 6 data points for this area was done. R Darveaux's constitutive model was applied for the data analysis such as the solder joint yields stress with respect to the time and temperature. On achieving the stress solution, the measured total strains were partitioned into elastic, plastic and creep terms separately and hence the creep strain was evaluated. From the analysis, it was found that the dominant deformation mode was shear deformation due to mismatch of coefficient of thermal expansion between pin and copper plating material of through-hole under thermal loading. And the dominant deformation mechanism was creep strain while stress started to relax at the end of ramp up and continued throughout the test and creep strain rate decreased during high temperature dwell. In Addition, the elastic strain was dominating during the initial stage of thermal cycle but later it was neglibible when compared to creep strain.

Thermo mechanical analysis of through-hole solder joint using strain partitioning method

Currently in the electronics industry there is a desire to increase component reliability. Fatigue failure in solder joints is an important design consideration for electronic packaging. In through-hole components, fatigue failure of leads has been observed to antecede fatigue failure of solder joints. The main objective of the study for a solder joint in a plated-through-hole bearing the pin during the temperature cycle was to ascertain the thermo mechanical behavior and the dominant deformation mode. The Digital Speckle Correlation (DSC) technique, which is a computer vision technique, was applied for the measurement of solder joint deforamtion for a prescribed outlined temperature and time. The dimensions for the area of the solder joint under study were 21 by 21 um, located at the centre of the hole. And computation of averaged shear strains at 6 data points for this area was done. R Darveaux's constitutive model was applied for the data analysis such as the solder joint yields stress with respect to the time and temperature. On achieving the stress solution, the measured total strains were partitioned into elastic, plastic and creep terms separately and hence the creep strain was evaluated. From the analysis, it was found that the dominant deformation mode was shear deformation due to mismatch of coefficient of thermal expansion between pin and copper plating material of through-hole under thermal loading. And the dominant deformation mechanism was creep strain while stress started to relax at the end of ramp up and continued throughout the test and creep strain rate decreased during high temperature dwell. In Addition, the elastic strain was dominating during the initial stage of thermal cycle but later it was neglibible when compared to creep strain.

3-D printed CDRA for radiation beam reconfigurability and beamforming in C-band

In this article, the design of a radiation beam-reconfigurable antenna using the reflector pins is presented. The reflector pins make a short or open connection with the ground, via switches and Plated Through Hole (PTH), which helps in controlling radiation characteristics of the proposed antenna. This design contains a simple 3D printed Cylindrical Dielectric Resonator Antenna that is located at the center of the substrate. The beam-sweeping of the antenna is attained by operating switches in different combinations of ON and OFF states. The reconfigurable CDRA operates at 4.5 GHz and covers all azimuth angles in four steps with a maximum measured gain of 6.6 dBi. This beam-switching antenna is very advantageous because of its trait of eliminating fade zones and beamforming.

Thermal Model of Printed Circuit Board Plated-Through Hole under One-Sided Heating Conditions

Thermal methods of quality control of the plated-through hole (PTH) of printed circuit board (PCB) are based on thermal models. However, known thermal models of PTH take no account of heat transfer to PCB material thus not allowing for PTH heat characteristic tying up with adhesion quality. In this work, an axisymmetric thermal model of a single-layer PCB PTH under one-sided heating conditions is considered. It was shown that the ratio of the temperature increments of the upper (heated) and lower end of the PTH in the considered range of heating power does not depend on the power level. A linear thermal equivalent scheme of the PTH has been proposed, which includes the longitudinal thermal resistance of the PTH metallization, de-termined by the parameters and quality of the metallization layer, the thermal resistance, which determines the convection heat exchange between the ends of the PTH with the adjacent PCB surface and the environment, and the thermal resistance of the area of the PCB material adjacent to the PTH, depending on the quality of the metallization adhesion and the PCB dielectric. Thermal equivalent circuit parameters determined by the ratio of the temperature increment of the upper and lower ends of the PTH and their difference can serve as the basis for the development of a nondestructive inspection procedure for PTH quality control by way of its unilateral heating, for example, by a laser beam.

A New Method for Non-Destructive Characterization of Through Holes in Printed Circuit Boards

Plated through hole (PTH) quality, including plating roughness, is a critical factor in the manufacture of reliable printed circuit boards (PCBs). Currently, cross-sectioning is most commonly used to assess PTH roughness but sectioning is a destructive process and offers a limited view of the PTH. Therefore, a non-destructive casting method using a silicone elastomer was developed to evaluate PTH roughness. Castings were successfully created from PTHs with aspect ratios as high as 22:1 and the castings accurately replicated the microtopography of the plating. Laser scanning microscopy was used to quantitatively measure the surface roughness of the castings which was shown to correlate to current induced thermal cycling (CITC) coupon cycles to failure, a measurement of PTH reliability. Thus, the casting technique can be used to quickly assess PTH quality and its effect on reliability. In addition to plating roughness, it was demonstrated that the casting technique can be used to evaluate back drill quality, PTH diameter along the length of the barrel, as well as drill and desmear processes by casting non-plated through holes.

Surviving the Heat Wave – A presentation on thermally induced failures and reliability risks created by advancements in electronics technologies

Since the advent of surface mount technology back in the 1970's we, as an industry, have continually worked to miniaturize our products. This evolution of product design has impacted us at the semiconductor, package, circuit board and system levels. So, the question is, Why do Electronics Fail Under Thermal Cycling? At the semiconductor level, you can have issues with delamination, IC complexity, degradation mechanisms, associated ceramic capacitor wearout, and electrical overstress (EOS). At the package level issues with bond wires and stacked die add to the reliability impact. At the printed circuit board level issues with solder wearout, solder phase coarsening, PWB laminates and glass materials, plated through hole (PTH) fatigue, and the impact of potting can also affect reliability while at the system level, heat sinks and other methods of heat removal can improve the situation. What drives these issues is that we use a variety of materials e.g. semiconductors, ceramics, metals and polymers. We then bond them together with other materials like solder and adhesives. Each of these materials has a Coefficient of Thermal Expansion (CTE) that is unique and therefore expands and contracts at different rates.