3 Layer PCB or Tri-layer PCB , Is less in the normally in the market, most most multilayer plural layer like 4 layer , 6 layer, 32 Layer.
Sometime some electronic device need special layer stack up to get the performance , and sometime ,just PCB designer want to save cost , not do 4 layer .
RayMing is 3 layer PCB manufacturer ,Welcome to send your design to firstname.lastname@example.org , We will give your quote asap
Multilayer PCBs have one or multiple conductor patterns inside the board, this increases the area available for wiring. By laminating or gluing several double-sided circuit boards together with insulating layers in between. Frequently between 3 and 8 layer PCBs are used as these offer the right amount of complexity for most purposes. There is the capacity for more layers however depending on device. These are likely to be different depending on the various device. Some smart phones for example are said to use 12 layers due to the various demands of the circuit. Often they have an even number of layers as odd layers can lead to issues with the circuit board. This includes problems like warping and twisting after soldering, and no cost savings as they’re not the standard to produce.