CSP: A Chip Scale Package is a type of package consisting of multiple integrated circuits (ICs). Initially CSP was abbreviated for Chip Size Package but was later changed due to the unavailability of packages of chip size.
A CSP is basically an encapsulation of one or more active, passive or other components into a single package by means of standard soldering methods thus increasing inner circuit connectivity and in turn reducing inner circuitry.
Interposers are electrical interfaces that allow spreading a connection to a broader pitch. It allows spreading of a signal or connection from on pitch to another. The die of the CSP is usually mounted on an interposer or the electric pads may be carved onto a silicon sheet or silicon wafer directly. Formation of such a packaging that is reduced to the size of a chip scale is extremely miniaturized and the method of packaging is called (WLP) or Wafer-level packaging.
The minimum criteria that needs to be met in order to form a CSP is a size constraint and the linear size of the package cannot exceed more than 1.2 times that of the flat IC fabricating material also known as die and the area of it cannot be more than 1.5 times that of 1.5 times that of the flat die. There can only be a single die for every package that allows mounting of electronics components. The ball pitch of a CSP is not to exceed 1mm.
There are a lot of chip scale packaging techniques being used as per the requirements that needs to be met while crafting a chip. Given the excessive variety of packages CSP can be distinctively categorized based on its area of usage, method or technology used to form the package and finally complete set of configuration of the package itself ie what it consists of. CSP is usually grouped as followed by their prospective manufacturers:
The typical materials and substances used for the manufacturing process of a CSP is similar to that of any other electromechanical components involving wires, leads, silicon , nickel and so on. There sure exists an exception when it comes to the redistribution by wafer-level methods.
The concept of a CSP or Chip Scale Packaging was first introduced by Fujitsu and Hitachi cable folks who collaborated to work on a project. The first official introduction was although by Mitsubishi Electric.
Each CSP style varies significantly from one another and so for a CSP to be substantially different from other external mountable parts which could be soldered, the assembly process needs to be focused on. The assembling of a CSP is focuses on the design and implementation of mountings and ICs on to a single chip and also focuses on the application aspect of it. A well designed CSP increases reliability if the filling material between substrate and mounted parts is efficient. Smaller die size, thinner die thickness, higher solder joint contact, efficient filling materials add to the overall functioning of a CSP.
The idea of having a single chip comprising of no terminal legs or leads is very intuitive and intriguing to a CSP designer. They are much simpler to fit by conventional soldering methods in comparison to standard chip making while protecting the flat bare die in the process. Chip Scale Packaging is the future of IC integration along with other mini components to form micro-chips that is used in over a billion electronics devices across the world.