Technical Library | 2023-01-17 17:27:13.0
Reflow profile has significant impact on solder joint performance because it influences wetting and microstructure of the solder joint. The degree of wetting, the microstructure (in particular the intermetallic layer), and the inherent strength of the solder all factor into the reliability of the solder joint. This paper presents experimental results on the effect of reflow profile on both 63%Sn 37%Pb (SnPb) and 96.5%Sn 3.0%Ag 0.5%Cu (SAC 305) solder joint shear force. Specifically, the effect of the reflow peak temperature and time above solder liquidus temperature are studied. Nine reflow profiles for SAC 305 and nine reflow profiles for SnPb have been developed with three levels of peak temperature (230 o C, 240 o C, and 250 o C for SAC 305; and 195 o C, 205 o C, and 215 o C for SnPb) and three levels of time above solder liquidus temperature (30 sec., 60 sec., and 90 sec.). The shear force data of four different sizes of chip resistors (1206, 0805, 0603, and 0402) are compared across the different profiles. The shear force of the resistors is measured at time 0 (right after assembly). The fracture surfaces have been studied using a scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS)
Technical Library | 2019-06-20 07:45:19.0
One of the two basic risks of employing the commercially accepted, Restriction of Hazardous Substances (RoHS) compliant, lead-free (Pb-free) electronics is the threat to the electronics reliability from the growth of tin whiskers. The other basic risk deals with Pb-free solder joint reliability.
Technical Library | 2019-06-19 11:06:46.0
Tin (Sn) metal displays the characteristic of growing “tin whiskers” from pure tin coatings (most actively on relatively thin, electrodeposited or immersion tin coatings), usually months or years from the initial deposition of the tin. Tin whiskers are electrically conductive, filamentary, single crystals of white (beta phase) tin. These filaments of single crystal tin are usually one to five microns in diameter, and a few microns up to several tens of millimeters long, that grow spontaneously from the tin coatings. Alloying additions of several percent (by weight) of lead (Pb) prevents these electrically conductive tin whiskers from growing. Pb alloyed into the Sn was discovered to prevent the occurrence of tin whiskers in electronic assemblies in the 1950s as the Bell Laboratories solution to the problem of tin whiskers. The alloying of the tin with lead has thus quietly averted incalculable losses from short circuits in electronic equipment for the last 60 years.
Technical Library | 2012-09-20 21:45:38.0
First published in the 2012 IPC APEX EXPO technical conference proceedings. An evaluation of four FR4 laminates in commonly used stack-ups was done to determine their survivability for the Pb-free HASL process followed by a worst case Pb-free manufacturin
Technical Library | 2022-10-31 17:09:04.0
The global transition to lead-free (Pb-free) electronics has led component and equipment manufacturers to transform their tin–lead (SnPb) processes to Pb-free. At the same time, Pb-free legislation has granted exemptions for some products whose applications require high long-term reliability. However, due to a reduction in the availability of SnPb components, compatibility concerns can arise if Pb-free components have to be utilized in a SnPb assembly. This compatibility situation of attaching a Pb-free component in a SnPb assembly is generally termed "backward compatibility." This paper presents the results of microstructural analysis of mixed solder joints which are formed by attaching Pb-free solder balls (SnAgCu) of a ball-grid-array component using SnPb paste. The experiment evaluates the Pb phase coarsening in bulk solder microstructure and the study of intermetallic compounds formed at the interface between the solder and the copper pad.
Technical Library | 2013-10-17 17:46:01.0
Although several commercial and experimental Pb-free solder alloys are available as replacements for Sn-Pb solders, the following families of solders are of particular interest and are the prevailing choices of industry: eutectic Sn-Ag, eutectic Sn-Cu, eutectic Sn-Zn, eutectic Bi-Sn, and Sn–In. Since the properties of the binary Pb-free solders cannot fully meet the requirements for applications in electronic packaging, additional alloying elements are added to improve the performance of these alloys. Thus, ternary and even quaternary Pb-free solders have been developed, such as Sn-Ag-Cu, Sn-Ag-Bi, and Sn-Zn-Bi solder...
Technical Library | 2012-09-27 19:50:01.0
First published in the 2012 IPC APEX EXPO technical conference proceedings. Over the past few years a new family of laminate systems has been developed to face the increasing physical demands of withstanding Pb-free soldering processes used in the assembl
Technical Library | 2015-01-08 17:26:59.0
Regardless of the accelerating trend for design and conversion to Pb-free manufacturing, many high reliability electronic equipment producers continue to manufacture and support tin-lead (SnPb) electronic products. Certain high reliability electronic products from the telecommunication, military, and medical sectors manufacture using SnPb solder assembly and remain in compliance with the RoHS Directive (restriction on certain hazardous substances) by invoking the European Union Pb-in-solder exemption. Sustaining SnPb manufacturing has become more challenging because the global component supply chain is converting rapidly to Pb-free offerings and has a decreasing motivation to continue producing SnPb product for the low-volume, high reliability end users. Availability of critical, larger SnPb BGA components is a growing concern
Technical Library | 2009-04-30 18:06:24.0
This presentation surveys the most significant via and via-related laminate failure mechanisms from past to present using data from current induced thermal cycling (CITC) testing, failure analysis, and other sources. The relative life and failure modes of thru vias, buried vias, and microvias (stacked vs. non-stacked) are compared, along with the affect of structure, materials, and peak temperatures on the above. The origin of via-induced laminate failures such as "eyebrow cracks" and Pb free related internal delamination is also explored.
Technical Library | 2015-11-19 18:15:07.0
The move to lead free (Pb-free) electronics by the commercial industry has resulted in an increasing number of ball grid array components (BGAs) which are only available with Pb-free solder balls. The reliability of these devices is not well established when assembled using a standard tin-lead (SnPb) solder paste and reflow profile, known as a backward compatible process. Previous studies in processing mixed alloy solder joints have demonstrated the importance of using a reflow temperature high enough to achieve complete mixing of the SnPb solder paste with the Pb-free solder ball. Research has indicated that complete mixing can occur below the melting point of the Pb-free alloy and is dependent on a number of factors including solder ball composition, solder ball to solder paste ratio, and peak reflow times and temperatures. Increasing the lead content in the system enables full mixing of the solder joint with a reduced peak reflow temperature, however, previous research is conflicting regarding the effect that lead percentage has on solder joint reliability in this mixed alloy solder joint.
