geologia: Lead

Evidence: 100 • authority: 72

Lead ( ) is a chemical element with the symbol Pb (from Latin plumbum) and has the atomic number 82. It is a heavy metal, meaning it is denser than most common materials. Lead is malleable and soft, meaning it can be shaped into different shapes and lead has a relatively low melting point. When freshly cut or melted, it appears shiny silvery with a bluish tint, but tarnishes to dull gray on exposure to air. Lead has the highest atomic number of any stable element, and three of its isotopes are endpoints of major nuclear decay chains of heavier elements. Lead is a relatively un-reactive post-transition metal. Its weak metallic character is shown by its amphoteric behavior: lead and lead oxid…

Evidence: 58 • authority: 72

Solder (UK: ; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable for use as solder should have a lower melting point than the pieces to be joined. The solder should also be resistant to oxidative and corrosive effects that would degrade the joint over time. Solder used in making electrical connections also needs to have favorable electrical characteristics such as low electrical resistance (high conductivity) and durable joints. Soft solder typically has a melting point range of 90 to 450 °C (190 to 840 °F; 360 to…

Evidence: 58 • authority: 88

Solder Joint Reliability of Different BGAs Reworked Using Low Melting Point Lead Free Alloys. ABSTRACT BGA packages with SAC (Sn-Ag-Cu) 385 balls were assembled on Printed Circuit Board (PCB) test vehicles using no clean SAC 385 paste. These components were then reworked using a new low temperature lead-free rework process. In this process, a solder alloy with a melting range lower than that of SAC solder was used. The lower process temperature introduces less risk of heat damage to both the reworked and adjacent components and well as to the board (cratering and board warpage). The microstructure of the resulting mixed solder joints when SAC 385 balls were assembled using low melt paste wa…

Evidence: 58 • authority: 72

The elements bismuth and indium have relatively low melting points when compared to other metals, and their alloy bismuth–indium (Bi–In) is classified as a fusible alloy. It has a melting point lower than the eutectic point of the tin–lead alloy. The most common application of the Bi-In alloy is as a low temperature solder, which can also contain, besides bismuth and indium, lead, cadmium, and tin.

Evidence: 50 • authority: 72

A fusible alloy is a metal alloy capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys. Sometimes the term "fusible alloy" is used to describe alloys with a melting point below 183 °C (361 °F; 456 K). Fusible alloys in this sense are used for solder.

Evidence: 50 • authority: 88

Sound population management ad infinitum: How relatively low fertility rates can lead to an "Evergreen demographic boon" Published in Google books, 2024. The term “Total fertility rate” also often abbreviated to TFR is a widely used, though somewhat misunderstood term today. The term has often been twisted and maligned in the press by reporters who have not understood the essence of the term. But what exactly is a total fertility rate? To put it in simple terms, the term “total fertility rate”, (which is a purely synthetic rate) in the average number of children a woman in a given society or culture could be expected to bear in her lifetime based on agespecific birth rates, assuming th…

Evidence: 50 • authority: 80

The Safety of Low Melting Point Bismuth/Lead Alloys: A Review

Evidence: 42 • authority: 72

A metal (from Ancient Greek μέταλλον (métallon) 'mine, quarry, metal') is a material that, when polished or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. These properties are all associated with having electrons available at the Fermi level, as opposed to nonmetallic materials which do not. Metals are typically ductile (can be drawn into a wire) and malleable (can be shaped via hammering or pressing). A metal may be a chemical element, such as iron, an alloy, such as stainless steel, or a molecular compound, such as polymeric sulfur nitride. The general science of metals is called metallurgy, a subtopic of materials science; aspects of their elec…

Evidence: 42 • authority: 80

Specification for Low Melting Point Alloys

Evidence: 42 • authority: 80

Specification for Low Melting Point Alloys

Evidence: 42 • authority: 88

Study of Application and Reliability of Low Melting Point Sn-Zn-Bi-In-P System Lead-Free Alloys. ABSTRACT The new Sn-Zn-Bi-In-P lead-free solder has good solderability, low melting point and the same reflow profile as the Sn-37Pb eutectic solder. The bonding strength of the Sn-Zn-Bi-In-P solder joint is 1.5 times higher than that of the Sn-37Pb solder joint. After thermal fatigue, the fatigue life of the former is 25% more than that of the latter. The microstructure and composition of the solder joint interface are also studied. A Zn-rich layer is found at the interface which can prevent the diffusion of Sn and Cu atoms, consequently decrease the thickness of the intermetallic compound laye…

Evidence: 42 • authority: 88

Development and Testing of a Lead-Free Low Melting Point Alloy. ABSTRACT This paper describes the development and testing procedure of a new lead-free low melting point alloy. Current lead-free soldering alloys involve soldering process temperatures that can be harsh on temperature sensitive electronic components and PCB materials. These temperature sensitive parts can be found on virtually every electronic unit. As a result electronic units can come out of the soldering process in an already aged condition, sometimes even damaged or pre-damaged. An obvious solution would be to lower the temperatures in those soldering processes. This however can only be realized when using soldering alloys…