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A solder bridge is an unintended electrical connection between two conductors by means of a small blob of solder. PCBs use solder masks to prevent this from happening. Solder mask is not always used for hand soldered assemblies, but is essential for mass-produced boards that are soldered automatically using reflow or wave soldering
Tin-silver-copper (Sn-Ag-Cu, also known as SAC), is a lead-free alloy commonly used for electronic solder. It is the main choice for lead-free surface-mount technology (SMT) assembly in the industry, [ 1 ] as it is near eutectic , with adequate thermal fatigue properties, strength, and wettability. [ 2 ]
Some key QFN design considerations are pad and stencil design. When it comes to bond pad design two approaches can be taken: solder mask defined (SMD) or non-solder mask defined (NSMD). A NSMD approach typically leads to more reliable joints, since the solder is able to bond to both the top and sides of the copper pad. [4]
Solder paste is applied to the location and reflowed. During reflow, solder flows and is drawn to the copper trace. Surface tension causes the bead to have a curved surface and rise above the solder mask, where it solidifies into a Bead Probe. The bead will be roughly obround in shape and may be 15-25 mils long. A properly constructed bead is ...
The most basic design rules are shown in the diagram on the right. The first are single layer rules. A width rule specifies the minimum width of any shape in the design. A spacing rule specifies the minimum distance between two adjacent objects. These rules will exist for each layer of semiconductor manufacturing process, with the lowest layers ...
The mask must be centered correctly. The mask protects the PWB against oxidation, and prevents unintended solder bridges from forming between closely spaced solder pads. Also the height of the solder mask should be lower than the pad height to avoid gasketing problems. If the height of the solder mask is greater than that of the pad, then some ...
Silver whiskers growing out of surface-mount resistors Metal whiskering is a phenomenon that occurs in electrical devices when metals form long whisker-like projections over time. Tin whiskers were noticed and documented in the vacuum tube era of electronics early in the 20th century in equipment that used pure, or almost pure, tin solder in ...
Both quantitative and qualitative tests for solderability exist. [6] The two most common testing methods are the 'dip and look' method and wetting balance analysis.In both of these tests, the soldered pieces undergo an accelerated aging process before being tested for solderability, to take into consideration the time a component was in storage prior to mounting to final assembly.