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Advice
 

Here is some advice how to design printed circuit boards that will work well and are at the same time easy to manufacture

Ground planes: ground plane

Boards may have ground planes, copper areas covering smaller or larger areas of the board, on one layer or several layers. The purpose is usually to achieve good electrical characteristics but sometimes also to achieve good heat dissipation.

If possible, leave 0,25 mm or more as isolation distance between the ground plane and solder pads and wires. The distance from the ground plane to the edge of the board should be at least 0, 5 mm (0,8 mm for V-score panels).

Connect the ground plane to the ground net, otherwise it is of no use. Delete small unconnected islands that may be generated by automatic methods to create the ground plane. If your layout program does not allow you to delete such, tell us and we will do it for you.

Border and milled openings:

pcb milled openingsBoards can have any boarder and any openings, however have in mind:

Inner corners get a radius of 1 mm as standard. On special request you can get 0,5 mm inner radius

The minimum slot width that can be routed is 0,8 mm

Solder mask:

By default the solder mask is green, but we also have black, white, red, blue and yellow solder mask as standard. To get very black boards the solder mask may be printed twice.

Please check that all solder pads have openings in the solder mask! This is especially important for new components that have been added to the component library.

various mask colors available

Peelable, temporary solder mask may be printed to protect certain areas during wave soldering.

Panels:

Boards may be delivered in panels, routed or V-scored, or a combination of both

Routed panels have a slot (usually 2,0 mm) beween the boards, all through the laminate

V-scored panels have a V-formed scoring on each side of the laminate, the laminate do not have any slots through the laminate

For V-cut the minimum distance from track or pad to the border of the board is 0,8mm

V-cut, scoring

Please do not forget to tell us about panel boarder, holes and fiducials

Plated holes:

plated holesDo not use smaller holes than neccessary. The cost of the boards increase with smaller holes. Holes 0,6 mm or greater give the lowest price.

Holes down to 0,2 mm can be used, for boards 2,0 mm or thicker the limit is 0,4 mm.

Minimum conductor width and distance:

conductorDo not use smaller conductor widths and distances than neccessary. Minimum conductor width and distance is 0,20 mm as standard. Please contact us if you need to use smaller geometry, usually this can be done.

If there is space enough, use smallest conductor and distance > 0,25 mm.

OSP:OSP - organic solderability preservative

OSP, Organic Solderability Preservative, is a thin and even coating especially suitable for SMT assembly. The coating gives good protection through multiple soldering cycles. Hand soldering is easier if flux is applied prior to soldering. Shelf life is very good, more than a year without any degradation in solderability.

Conductor width and current:

There is no easy formula to calculate conductor width for a certain current. Standards give the relationsship between conductor area, current and temperature rise. These figures are valid under certain circumstancies, other values may be valid for a specific board. Some advice:

Wider conductors allow higher current, double width allows almost double current

Thicker conductors allow higher current, double copper thickness allows approx 60 % higher current

Inner layers in multilayer boards allow less current due to less heat dissipation

Rough values for 1 oz (35 um) copper and 15 degrees Celsius temperature rise: 0,5mm conductors 2A, 1,0mm conductors 4A and 5mm conductors 11A

Rough values for 2 oz (70 um) copper thickness and 15 degrees Celsius temperature rise: 0,5mm conductors 4A, 1,0mm conductors 6A and 5mm conductors 13A

Component notation: silk screen print

The component notation is white by default but can be printed in the same colours as the solder masks. Several colours may be used to print a logotype or similar on the boards.

Please check that no part of the component notation is on solder pads. By default we clean the solder pads from component notation, but you may loose information. Please also take in account that the tolerance for component notation is +/- 0,4 mm.

Galvanic platings: Gold

Different types of connectors can be plated with hard gold (gold over nickel) or palladium. Hard gold is more common but palladium plating is harder and more durable.

galvanic gold platingConnectors plated may be edge connectors or connectors anywhere on the board if a electrical connection can be achieved. Please contact us if you have questions!

To the topUpdate: 25.01.2013

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