Chip Carrier is the container used to enclose the IC or Transistors. Chip Carrier is also known as the Chip package which has metal leads or pins for electrical connections. The metal pins are strong enough to hold the chip package in the circuit board or in ZIF sockets. The pins of chip packages vary from 2 to 1000 as in Microprocessor chips. Common transistors have 3 or 4 pins and ICs have 8, 14, 16 or 18,28 pins etc.
Pin connections of ICs
Most of the ICs are DIP or DIL (Dual In line Package) package with two parallel rows of pins. These ICs are rectangular in shape and the pins point downwards enough to go through the holes of the PCB. The pins are soldered to the track side of the PCB so that the pins make electrical contact with the copper tracks.
DIP ICs can be directly soldered on the PCB or fixed in an IC base so that the IC can be replaced easily. Use of IC base also prevents the damage of IC due to soldering heat.DIP package also helps to mount ICs in Bread board or Prototyping Common PCB.
Lead counting of DIP ICs
The pins of DIP ICs are numbered from 1 starting from the left side. The pins of ICs can be easily identified by the following method.
- Keep the IC with the Half moon shaped Notch facing the left hand side so as to read the IC number.
- The pin just below the Notch is Pin1.This Notch helps to identify the orientation of IC as well as useful to automated chip insertion machinery to orient the IC in correct position.
- Count the pin numbers as 2, 3 etc in the Anticlock wise direction. The last pin is at the opposite side of Pin1.
- In most of the ICs, there is a Dot above pin1. This helps to identify pin 1, if the notch is absent.
Use of IC Base
It is better to use IC Base for fixing ICs. If IC base is used, it can be easily replaced without desoldering that may damage the PCB tracks. Fixing IC in the socket also protect the IC from heat damage during soldering. The pin arrangement of IC base is similar to DIP IC and there is a Notch at the left side. IC is inserted into the IC base with both the notches of IC and IC base are in same orientation so that pins will be same as in circuit diagram.
There are different types of IC bases based on the pin number of ICs. These are 6 pin, 8 pin, 14 pin, 16 pin, 18 pin, 28 pin bases etc. In microprocessor ICs ,there may be hundreds of pins.