Multilayer PCB is a circuit board that has more than two layers. Unlike a Double-Sided PCB which only has two conductive layers of material, all multilayer PCBs must have at least three layers of conductive material which are buried in the center of the material.
How Are Multilayer PCBs Made?
Alternating layers of prepeg and core materials are laminated together under high temperature and pressure to produce Multilayer PCBs. This process ensures that air isn’t trapped between layers, conductors are completely encapsulated by resin, and the adhesive that holds the layers together are properly melted and cured. The range of material combinations is extensive from basic epoxy glass to exotic ceramic or Teflon materials. Multi-layer printed circuit boards have trace layers inside the board. This is achieved by laminating a stack of materials in a press by applying pressure and heat for a period of time. This results in an inseparable one piece product. For multi-layer boards, those with three layers or more, drilling typically produces a smear of the high temperature decomposition products of bonding agent in the laminate system. In a multi-layer board one entire layer may be mostly solid copper to act as a ground plane for shielding and power return.
Benefits of Multilayer PCBs
-Higher assembly density
-Smaller size (considerable savings on space)
-Easier incorporation controlled impedance features.
-EMI shielding through careful placement of power and ground layers.
-Reduces the need for interconnection wiring harnesses (reduces overall weight)
Application of Multilayer PCB
Multilayer circuit boards were essential in the advancement of modern computing. The multilayer PCB basic construction and fabrication are similar to micro chip fabrication on a macro size. The range of material combinations is extensive from basic epoxy glass to exotic ceramic fills. Multilayer can be built on ceramic, copper, and aluminum. Blind and buried vias are commonly produced, along with pad on via technology.
-Cat scan technology
-Cell phone transmission
-Cell phone repeaters
-Central fire alarm systems
-Fiber optic receptors
-Nuclear detection systems
-Space probe equipment
-Hand held devices