catalog - LPKF Laser & Electronics - #101

The production of a double-sided printed circuit board is quite simple. Only the two (top/bottom) copper layers of the base material are milled. Depending on the through-hole plating process, the printed circuit board may be plated before or after structuring.

The production of a multilayer board is more elaborate, since it consists of several layers which must be bonded to a printed circuit board. The external layers of a multilayer PCB consist of single sided base material. The inner layers are usually composed of standard double-sided board material. Sometimes however, the use of single sided base material is also necessary in the inner layers in order to fulfill the required electrical characteristics of a specific design. The thickness, and number of Prepreg sheets inserted between the conductive layers determine the electrical characteristics of a multilayer PCB. Compared to a double-sided printed circuit board, besides the additional milling work, the manufacturing step of lamination is necessary to create a multilayer.

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For the structuring of a 6 to 8-layer multilayer the inner layers, 2 and 3, as well as the inner layers, 4 and 5, are milled first. Afterwards, the two structured inner layers and the two external layers, with Prepreg inserted between, are bonded together. Since a 6-layer multilayer can only be electroplated, the printed circuit board is plated before the final milling of the external layers.

For the structuring of a 4-layer board, the inner layers, 2 and 3, are milled first. When using the chemistry-free through-hole conductivity, the external layers are milled afterwards. Then, the structured inner layers and the two structured external layers, with inserted prepregs in between, are bonded to make multiple layers. When using electroplating, the external layers of the finish-bonded multilayer are milled after the plating process.

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pressure plate

layer 1

2x prepreg

layer 2&3

2x prepreg layer 4

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4-layer multilayer

6-layer multilayer