RECOMMENDATIONS AND TECHNICAL CAPABILITIES

The limitations for width and separation between conductors depends on the based copper. The table below sums up the manufacturing options:

External layers

Copper base*Minimum width (Tw)Minimum gap (Ts)
18µ0.125mm0.150mm
35µ0.200mm0.200mm
70µ0.250mm0.250mm

Internal layers

Copper baseMinimum width (Tw)Minimum gap (Ts)
18µ0.125mm0.150mm
35µ0.150mm0.180mm
70µ0.250mm0.250mm

The most important characteristics of the drills on the printed circuit board are: diameter, if they are plated or non plated and their depth. The last characteristic is determined by the thickness of the base material, and is key in determining the minimum drill possible as described in the calculation section.

Minimum annular rings

Drilling typeMinimum drilling diameter
Plated0.250mm
Non plated0.350mm
Blind via0.500mm

Final diameter tolerances

Drilling typeTolerance
Plated+0.1mm/-0.05mm
Non plated+0.1mm/-0.05mm

Calculate Aspect Ratio:

The Aspect Ratio is the relationship between the minimum manufacturable drilling on the thickness of the circuit board, following the formula below:

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Aspect ratio ≤ 6.

The annular ring is the metal ring left around the drilling on a pad.

Minimum annular ring

PlatedMinimum annular ring (Cm)
Cu Base+18µ0.150mm
Cu Base+35µ0.200mm

Internal layers

PlatedMinimum annular ring (Cm)
18µ , 35µ , 70µ0.200mm

The solder mask is a coating put on to protect the printed circuit board, so that it cannot be soldered on except in designated areas.

ColourMinimum margin (Mc)Minimum width (Mb)
Green0.075mm0.100mm
White, black, grey, blue, red0.075mm0.150mm

Note: except when otherwise specified, the mask will be adapted by eliminating traces smaller than the minimum trace and expanding it to the minimum margin.

Used to reference the components and indicate their position and dimensions on the printed circuit board, can also include logos, circuit board codes, quality marking and any images that comply with the minimum parameters for production capacity.

ColourMinimum width (Mi)Minimum trace margin/soldermask (Mt)
White0.125mm0.100mm
Black0.180mm0.100mm

Note: except when specified otherwise, all marking images coinciding with areas without solder mask will be eliminated.

CNC milling is an automatic cutting system that uses a rotating tool guided by a numerical control system. The mechanical options for milling done with this process are determined by the precision of the numerically controlled machine and the diameter of the tool used, the latter being the only variable the designer may change.

Mechanical options

ConceptsFigures
Minimum tool diameter (Sm)0.80mm
Minimum radius for internal windows (Rm)0.40mm
Position tolerance+/-0.20mm
Minimum Copper-Edge gap (Cg)0.20mm

Plated Edges/Castellated holes (half holes)

Type of process used to connect circuit boards. It consists in putting a metallic cover on the sections at the edge of the circuit board to allow for lateral soldering and electric union between layers.

Plated Edges

ConceptsFigures
Minimum legth (Pc)1.50mm
Minimum separation between lengths (Nc)0.80mm
Position tolerance+/-0.20mm
Size tolerance+/-0.10mm

Castellated holes (half holes)

ConceptsFigures
Minimum drill (Dm)0.80mm
Minimum annular ring (Ar)0.20mm
Minimum separation between pads0.20mm
Position tolerance drill/edge+/-0.20mm
Size tolerance+/-0.10mm

Bevelling

Type of mechanisation used to facilitate insertion of circuit boards into card-type connectors (e.g. PCI, AGP, ISA, etc.). This reduces the edge of the circuit board where the connector is located to 30°.

Note: this process affects the whole length of the edge of the circuit board where the connector will be located, even if it doesn’t take up the whole length. This process should not be used on top of the metallic area of a circuit board, so it is recommended to apply the following formula:

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Conical Countersink

Type of process used to embed the head of screws with a cone shape. It is a 45° groove drill on one of the sides of the circuit board.

Note: the maximum upper diameter (Da) is determined by the following formula:

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Flat Countersink

Type of process used to embed the head of screws with a flat shape. It is a 90° groove drill on one of the sides of the circuit board.

Grooves

Process required to assemble certain types of components such as contactors, joysticks onto the PCB or for components that cannot stick out above the surface of the PCB, membrane keyboards for example.

Scoring or V-cut consists in creating two grooves in a V shape on either side of the circuit board coinciding with the axis that divides them. The hold force between the circuit boards is determined by the size of the core left between the two V-cuts.

Applicable figures

ConceptsFigures
Minimum material thickness0.50mm
Maximum material thickness2.40mm
Position tolerance+/-0.10mm
Minimum separation between Copper – Edge (Cs)0.40mm for base material thickness 0.8mm
0.50mm for base material thickness 1.6mm
0.70mm for base material thickness 2.4mm
Slot angle30º

Note: Recommended use of V-cut depaneling machine. After separating the circuit boards, the absolute measurements of the circuit boards may vary +/- 0.30 mm.