A high quality component library plays an important role in designing a high quality PCB Layout. In most of the PCB Design Software, Component Libraries will have hundreds of components by default which comes along with the software.
Each PCB Design Software has its own method of creating Layout Footprint for the components but the data required is same for all software. The first step is to analyse the datasheet or any other input given for Footprint creation. Analysis of data and good understanding is important. For example, designer should know the difference between the silkscreen outline and assembly outline. There are two methods in Footprint creation, one is Manual method and the other one is Creation using Wizard. Using wizard method, footprint creation can be done quickly. This method can be used for standard packages only. Some of the standard packages are
- QUAD Packages
In this method, when the required data are given as input the footprint will be created in few seconds which is an advantage over the manual method.
Drill size, pad size, pitch, number of pins, component dimensions, etc required for footprint creation can be calculated from the data given in the datasheet. It is important to know how to analyse the datasheet and use the data for footprint creation. The measurement units given in the datasheet is also important to consider while creating footprint. Most of the component manufacturers are providing their component package dimensions and pin pitches in metric units. So, it is better to use metric units for footprint creation. Customer wants to design the PCB Layout in anyone of the following units
If the Layout design is done in inches or mils, the components in library having metric units will be converted to inches or mils during placement.
IPC standards are available for Footprint creation for Surface mount devices, Plated through-hole and a combination of the two technologies. The standard IPC-7351B is one of the IPC standards for Footprint creation. It is better to have knowledge about IPC standards which will help in creating a high quality component library.
Many processes starting from component placement upto assembly process depends on the quality of component library. There are lot of things a designer should know and consider the same to create a high quality component library.