Via in Pad PCB board description:
Surface finish: immersion gold
Via in pad PCB:
via-padsIn PCB design, via refers to a pad with a plated hole that connects copper tracks from one layer of the board to other layer(s). High-density multi-layer PCBs may have blind vias, which are visible only on one surface, or buried vias, which are visible on neither, normally referred to as micro vias. The advent and extensive use of finer pitch devices and requirements for smaller size PCBs creates new challenges. An exciting solution to these challenges uses a recent, but common PCB manufacturing technology with self descriptive name, “via in pad”.
Via in pad helps to reduce inductance, increase density and employ finer pitch array packages. The via in pad approach places a via directly under the device’s contact pads. This allows higher component density and improved routing. Consequently, via in pad provides the designer significant PCB space savings. For example, traditional fan-out places four components, whereas with via in pad, six components can be placed within the same board outline.
Filled via in pad is a way to achieve intermediate density with an intermediate cost compared to using blind/buried vias. Some of the key advantages associated with using the via in pad technology are:
Fan out fine pitch (less than .75mm) BGAs
Meets closely packed placement requirements
Better thermal management
Overcomes high speed design issues and constraints i.e. low inductance
No via plugging is required at component locations
Provides a flat, coplanar surface for component attachment
The benefits of via-in-pad designs are well documented. From reduction of inductance to increased density, via-in-pad has become an essential tool for designers when navigating the routing challenges of fine pitch array packages that have become mainstays in today’s BOMs but there are trade-offs that must be considered.
The basic concept is elegant. The via-in-pad design methodology allows the designer to place the via right beneath the component contact pad. Hence the reduction of inductance plus the added benefit of improved routing density which can lead to higher density per layer. The net result is more routing in less space and a smaller PCBs footprint. It is another miniaturization tool that can drive cost down.
However, there are trade-offs when implementing via-in-pad technology. The process may increase the PCB cost. The reason is that the via-in-pad technique requires both additional process steps and extra materials. Added costs are found in both the extra materials used, including epoxy or metal based via fill materials and copper cap plating processes, as well as added process steps like vacuum via fill, curing, planarization and secondary plating operations. There is also the general challenge that results from producing a higher density PCB.
Via in pad Computer PCB boards:
Prior to the invention of the microprocessor PCB, a computer consisted of multiple printed circuit boards in a card-cage case with components connected by a backplane, a set of interconnected sockets. In very old designs the wires were discrete connections between card connector pins, but printed circuit boards soon became the standard practice PCB. The Central Processing Unit, memory and peripherals were housed on individual printed circuit boards which were plugged into the backplate.
During the late 1980s and 1990s, it became economical to move an increasing number of peripheral functions onto the motherboard. In the late 1980s, personal computer motherboards began to include single ICs (also called Super I/O chips) PCB capable of supporting a set of low-speed peripherals: keyboard, mouse, floppy disk drive PCB, serial ports, and parallel ports. By the late-1990s, many personal PCB computer motherboards supported a full range of audio, video, storage, and networking functions without the need for any expansion cards at all; higher-end systems for 3D gaming and computer graphics typically retained only the graphics card as a separate component PCB.
The most PCB popular computers such as the Apple II and IBM PC had published schematic diagrams and other documentation which permitted rapid PCB reverse-engineering and third-party replacement motherboards. Usually intended for building new computers compatible with the exemplars PCB, many motherboards offered additional performance or other features and were used to upgrade the manufacturer's original equipment.
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