Technological data concerning the production of PCBs
in Basista Printed Circuit Boards company
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4.1 General remarks concerning the multi-layer PCBs.
Due to their specific character, the multi-layer boards deserve a few additional remarks. Production of multi-layer boards requires considerably higher precision than the one needed for the production of single – sided and double – sided boards.
Particular attention should be paid to the ratio of pads diameter (counter-pads for inner copper coated layers) to holes diameter. Too small difference between those diameters can often be a cause of short-circuits in the board. The proper values of counter-pad and hole diameters are presented on the following drawing.
D1 – insulation diameter
D2 – pad diameter
d – metal-plated hole diameter
To maintain the correct sequence of layers, every layer should contain information on its position written inside the board outline.
z.B..: Top – 1Mid1 – 2
Mid2 – 3
Bottom – 4
Such information will significantly contribute to the correct interpretation of data and board assembly.
Structure of a multi-layer PCB
4.2 Data concerning mechanical treatment of multi-layer PCBs
1. Maximum dimensions of printed circuit board 421 x 573 mm
2. Standard final thickness of multi-layer PCB 5 mm +/- 10 %
3. Standard cooper thickness for inner layers 18 µm
for outer layers 35 µm
4 Tolerance4.2.1 Routing +/- 0,10 mm
4.2.2 Standard contour routing milling cutter - 2mm
1. Drilling accuracy +/- 0,05 mm [2 mils]
2. Minimum hole diameter for standard PCBs = 0.20 mm
(thickness of laminate up to 1,55 mm)
3. Standard hole diameter = 0.30 mm
4. Tolerance of non-plated holes +/- 0,10 mm
5. Tolerance of metal-plated holes – all diameters + 0.10 mm / -0.05 mm
6. Holes bigger than 6 mm are routing
1. Minimum pad diameter hole diameter + 0,4 mm
4.5 Electric connections - tracks
1. Minimum track width (inner layers) 6 mils
2. . Minimum distance between tracks (inner layers) 5 mils
4.6 Photo resist mask applied with use of curtain method
1. Green colour, applied with use of curtain method - as standard
2. Other colours - on request (silk-screen printing technology)
3. Maximum copper thickness - 105 µm (in case of higher thickness values, the mask is applied with use of silk-screen printing technology)
4. Guaranteed minimum thickness of layer measured from the track edge - 10 µm
Thickness of layer 250 µm
2. Maximum diameter of hole covered with mask 2,0 mm
Caution! Bigger holes, when covered with removable mask, may be covered incompletely.
4.8 Silkscreen
1. Thickness of text line 6 mils
2. Standard colour - white
3. Other colours on request
4.9 Structure of some exemplary multi-layer PCBs
Guaranteed distances between the inner and outer layers in multi-layer PCBs
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