User Guide

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
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nents available is, however, so wide that it is impossible to supply librar
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ieswhicharesuitableforeveryuserwithoutmodification.
There are even different packages which are supplied by various manu
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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
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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
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nufacturingData (Chapter9).
97
FromSchematictoFinishedBoard