jedzenie: 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: 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: 50 • authority: 80

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

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: 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…

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…