Tips for PCB Package
PCB designers who have designed a hardware may have done their own component or module package. However, it is not an easy job to do a good package, most designers may have had the following experience:
1.Too large or too small spacing between package pins can not be assembled;
2.To correspond to the schematic, if you draw a reverse packaging, you need to install component or module on the opposite side;
3.Sometimes, the size you design is different from the component or module you bought, then that not be assembled;
4.Too large or too small packaging outline may lead to the sense of uncomfortable;
5.Dislocation between designed and actual packaging outline, in particular, some mounting hole are wrongly placed, will cause screw failure.
Assign component package after drawing the schematic, it is recommended to use the system package library or company package library package. However, sometimes we still need to do our own packaging, what should we pay attention to avoid unnecessary problems?
First of all, we must have the package size of the component or module which generally suggested in a datasheet. Some datasheet suggest component packages, then we should follow the datasheet to do the design package. If the datasheet only gives the overall dimensions, then the package size should be 0.5mm-1.0mm larger than outline size. If the space allows, it is recommended to add an outline or frame to the component or module package; if the space is limited, you can choose to add an outline or frame to some of the components.
There are some international norms on the package of components, you can refer to IPC-SM-782A, IPC-7351 and other related information.
After you draw a package, please make sure you have done correctly as per the following questions.
1.Is the pin pitch correct?
2.If the pad design is reasonable?
3.Did you design the package from Top View's perspective?
4.Is the position of Pin 1 and Pin N correctly?
5.Did you mark the Pin 1?
6.If the package needs mounting holes, then is the package of mounting holes’ position correct?
7.Did you design an outline for the component or module?
8.For ICs with a large number of pins, have you marked pins of 5X and 10X?
9.If the various markings and outline size is reasonable?