Via (electronics)
Via ( coll by Steiger, English vertical interconnect access, abbreviated VIA ) is a vertical electrical connection between the conductor layers of a PCB. The connection is usually achieved by an internally metallised hole in the substrate material of the printed circuit board. Rarely, rivets and studs are used.
Vias are also found in integrated circuits (IC). Again, vias vertical electrical connections between two metallization. The manufacture of the IC is performed, however, gradually vias by etching of metal layers or the deposition of metal in the non- patterned conductive layers, see, damascene, and dual damascene process. Another form of vias are silicon vias to enable electrical connections between the vertical stacked microchips for future 3D integrated ICs.
Production
Vias are produced by the hole seeded in the carrier material ( with a catalyst used), then metallized catalytic and then, if necessary, reinforced electrolytically (building a thicker metal layer). This technology differs from the production of the conductive paths (which can be prepared with a Maskenätzverfahren ) corresponding printed circuit boards are referred to as plated-through printed circuit boards ( DKL ). PCB without vias are accordingly referred to as NDKL.
Subsequently you can deliver the pads fit purely mechanically by means Durchkontaktiernieten, see picture.
Use
The via hole can simultaneously serve as a pad for wired components ( through hole ) or be only appropriate for the purpose of making electrical contact.
Vias can also or only serve to improve the vertical heat conduction (thermal vias ).
A plurality of vias for reducing the lead inductance or to increase the current carrying capacity of a compound often incorporated in parallel.
Depending on the use, the diameter and, if the shape is different. Smaller vias are drilled in printed circuit board manufacture. Moreover, there is the possibility that more vias to be milled and hence other geometries (for example, slots ) can be prepared.
With the aid of plated-through holes, it is possible to change the conductor layers in two - layer or multilayer printed circuit boards. This is the prerequisite for disentangling complex circuits.
If the hole of the via has a very small diameter, they are called also micro-via. Micro-vias are often drilled with a laser.
Is not it enough the via through the whole board, but only up to the middle layers, they are called blind via. If there are "buried" vias only between middle layers, they are called buried via.
Assembly
SMD components
Leaded components are increasingly being replaced by Leadless Surface Mounted Devices, therefore, today's boards have a larger number of vias that receive no component. In the field of SMD solder joints should be no vias, as in soldering liquid solder can flow into the via, thus leading to a lean solder joint. Let in the pad area of SMD components but not avoid vias, a sufficient solder reservoir must be provided by thicker solder paste. It is also possible to cover the vias with adequate processes or to close.
THT components
If ( wired ) components are soldered to vias, the vias are filled with solder. This improves the connection of the component to the PCB, however, this must tin for desoldering the components to be removed again, which makes it difficult to repair such components.
Robustness of the circuit board
Through -hole PCBs provide a better grip and more reliable connection of wired components. They are therefore common even for simple assemblies of high quality. In addition to the adhesive bonding of the individual layers of the circuit board, the metallized vias provide a better cohesion of the board.
- Construction and connection technology of the electronics