Multilayer printed circuit boards (PCBs) represented the next major evolution in fabrication technology. From the base platform of double sided plated thru came a very sophisticated and complex methodology that would again allow circuit board designers a dynamic range of interconnects and applications. 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. Manufacturing multilayer circuit boards is a straightforward process but does require a high level of attention to detail. PCB Manufacturing multilayer PCBs requires a specialized hydraulic press with heated platens.
The multilayer PCB is made up by two or more pcbs which are stacked together with reliable predefined mutual connection between them. There are at least three conductive layers in one multilayer PCB with two layers outside and the one layer synthesized in the insulation board. Due to the complex manufacturing process and lower production , the cost of multilayer pcb is relatively higher. Multi-layer PCB needs further design attention as we have to keep some points into consideration from manufacturing perspective:
• Copper areas – on inner layers, all copper should be kept at least and largest value.
• Via clearance through inner layers (antipads)
• Allow for clearance around any holes or via barrels not connected to an inner layer. This clearance should be at least 15 mil although 20 mil clearance is preferred.
• Thermal Relief Pads – the tie should be a minimum of 8 mil while more is preferable.
• Larger geometries – will result in higher yields which will be reflected in your board price.
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4 layer stamp vias with 2um immersion gold 0.1mm vias mobile pcb 4 layer red solder mask pcb
Max. board size
Max. board thickness
Min. board thickness
Min.mechanical drilling via diameter
Min.laser drilling via diameter
Min. outer base copper
Max. outer base copper
Min. inner base copper
Max. inner base copperPTH aspect ratio
Blind via aspect ratio
Mechanical drilling tolerance
Min. core thickness
Outer layer min trace/space
inner layer min trace/space
Min fine pitch
Control impedance tolerance
28’’ x 42’’
5mil bigger than the inner pad