cadsoft eagle 4.5 Manual De Usuario

6.2 Considerations Prior to Creating a Board

Checking the Component Libraries

The EAGLE component libraries are developed by practicing engineers,

and correspond closely to present-day standards. The variety of compo-

nents available is, however, so wide that it is impossible to supply librar-

ies which are suitable for every user without modification.
There are even different packages which are supplied by various manu-

facturers using the same identification! Manufacturers recommend very

different sizes for SMD pads, and these depend again on the soldering

procedure being applied.
In short: You cannot get away without checking the components, in

particular the package definitions, being used when laying out.
In the case of SMD components please take particular care to ensure that the

package from the library agrees with the specifications of your component.

Housings from different manufacturers with the same name but different

dimensions are often found.

Agreement with the Board Manufacturer

If you plan to have your pcb films made using a Gerber photoplotter,

then, if you have not already done so, now is the time to inquire at your

board maker whether he stipulates any particular values for the follow-

ing parameters:

• track width
• shape of solder lands
• diameter of solder lands
• dimensions of SMD pads
• text size and thickness
• drill hole diameters
• number of signal layers
• in case of multilayer boards: manufacturing directions for blind

and buried vias and composition of the board

(see page 121)

• distance between different potentials
• parameters concerning solder stop mask

You will save yourself time and money if you take these stipulations into

account in good time.
You will find more details on this in the section on the Preparing of Ma-

nufacturing Data (Chapter 9).

From Schematic to Finished Board