Technical Library | 2023-01-17 17:22:28.0
The impact of voiding on the solder joint integrity of ball grid arrays (BGAs)/chip scale packages (CSPs) can be a topic of lengthy and energetic discussion. Detailed industry investigations have shown that voids have little effect on solder joint integrity unless they fall into specific location/geometry configurations. These investigations have focused on thermal cycle testing at 0°C-100°C, which is typically used to evaluate commercial electronic products. This paper documents an investigation to determine the impact of voids in BGA and CSP components using thermal cycle testing (-55°C to +125°C) in accordance with the IPC- 9701 specification for tin/lead solder alloys. This temperature range is more typical of military and other high performance product use environments. A proposed BGA void requirement revision for the IPC-JSTD-001 specification will be extracted from the results analysis.
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 | 2007-08-16 13:34:31.0
While experienced inspectors may be able to determine the aesthetic differences between a lead-free PCB assembly and a tin-lead version, one cannot rely on the "experienced eye". "Less wetting out to the pad edges" (Figure A) and "graininess and lack of shininess of the solder joint" (Figure B) are typical comments about some lead-free solder joints. However, in cases where a Nitrogen atmosphere was present during the reflow of the solder joint (Figure C), there will be little visual differences between the lead free alloys and their tin-lead counterparts.
Technical Library | 2013-01-24 19:16:35.0
The electronics industry has mainly adopted the higher melting point Sn3Ag0.5Cu solder alloys for lead-free reflow soldering applications. For applications where temperature sensitive components and boards are used this has created a need to develop low melting point lead-free alloy solder pastes. Tin-bismuth and tin-bismuth-silver containing alloys were used to address the temperature issue with development done on Sn58Bi, Sn57.6Bi0.4Ag, Sn57Bi1Ag lead-free solder alloy pastes. Investigations included paste printing studies, reflow and wetting analysis on different substrates and board surface finishes and head-in-pillow paste performance in addition to paste-in-hole reflow tests. Voiding was also investigated on tin-bismuth and tin-bismuth-silver versus Sn3Ag0.5Cu soldered QFN/MLF/BTC components. Mechanical bond strength testing was also done comparing Sn58Bi, Sn37Pb and Sn3Ag0.5Cu soldered components. The results of the work are reported.
Technical Library | 2012-10-23 14:25:38.0
Tin-Silver-Copper alloys are the primary choice for lead-free SMT assembly. Although there are other options available such as alloys containing bismuth or indium and other elements, tin-silver-copper solders, also known as SAC alloys are by far the most popular. They are used by approximately 65% of users, as last surveyed by Soldertec in 2003.
Technical Library | 2008-01-03 17:50:51.0
Lead-free SMT can be achieved reliably if several process requirements are implemented carefully. Some of the variables to account for are listed below. The most common alloys used in lead-free SMT are tin-silver-copper alloys; these alloys all have a meting range between 217- 220°C. These alloys all melt at higher temperatures than traditional leaded solders such as the 63/37which has a melting point of 183 °C.
Technical Library | 2016-02-18 18:55:09.0
As lead-free alloys shift into high reliability electronics, the issue of tin whisker growth remains a primary concern among those in the industry. Current research shows that there is no perfect alloy for all cases of electronic usage. Industry leaders and researchers continue to study and search for a lead free alloy that is able to withstand harsh environments while maintaining high reliability.
Technical Library | 2009-01-15 00:42:58.0
Tin-silver-copper has received much publicity in recent years as the lead-free solder of choice. SAC305 was endorsed by the IPC Solder Value Product Council in the United States as the preferred option for SMT assembly; most assemblers have transitioned to this alloy for their solder paste requirements. The SAC305 alloy due to its 3.0% content of silver is expensive when compared to traditional 63/37 for this reason many wave assemblers are opting for less costly options such as tin-copper based solders for their wave, selective and dip tinning operations.
Technical Library | 2013-08-22 14:28:58.0
Tin-rich solders are widely applied in the electronic industry in the majority of modern printed circuit boards (PCBs). Because the use of lead-tin solders has been banned in the European Union since 2006, the problem of the bridging of adjacent conductors due to tin whisker growth (limited before by the addition of Pb) has been reborn. In this study tin alloys soldered on glass-epoxy laminate (typically used for PCBs) are considered. Scanning ion microscopy with Focused Ion Beam (FIB) system and energy-dispersive X-ray spectroscopy (EDXS) were used to determine correlations between spatial non-uniformities of the glass-epoxy laminate, the distribution of intermetallic compounds and whisker growth.
Technical Library | 2016-05-26 15:07:36.0
The oxide layers are known as wetting inhibitors in component and PCB metallizations. The oxide acts as barrier that prevent the tin diffusion from happening. Besides, in corrosion studies, the role of salt residues -with Cl ion- on some metals is known as being promoters of oxidation or corrosion. On the other hand, most of corrosion studies with tin metallization are focused mainly on the corrosion resistance of tin alloys, but little has been done respecting to the influence of salts on tin metallization wetting. In this paper, a series of experiments was carried over to know the influence of specifically NaCl on BGA wetting given Head in Pillow (HiP) as result.
