CSP, 0201 passive components, lead-free soldering and optoelectronics are the hot advanced technologies that many companies have been practicing and actively evaluating on PCB recently.
For example, how to deal with the problem of super small opening (250um) that is common in CSP and 0201 assembly is the basic physical problem of solder paste printing that has never existed before.As a large developing field in communication and network technology, board - level optoelectronic assembly has a very delicate process.Typical packaging is expensive and fragile, especially after the device leads are formed.The design guidelines for these complex technologies are also very different from normal SMT processes, as board design plays an even more important role in ensuring assembly productivity and product reliability;
For example, for CSP welding interconnections, reliability can be significantly improved simply by changing the size of the plate bond plate.
One of the key technologies that people use today is CSP.The charm of CSP technology lies in its many advantages, such as reduction of package size, increase of pin number, function/performance enhancement, and repairability of package.
The efficient advantages of CSP are as follows: when used for board level assembly, CSP can cross the boundary of the peripheral package of fine spacing (as small as 0.075mm) and enter the regional array structure of large spacing (1,0.8, 0.75, 0.5, 0.4mm).Many CSP devices have been used in consumer telecommunications for years, and are widely considered to be low-cost solutions in the areas of SRAM and DRAM, mid-pin ASIC, flash memory, and microprocessors.
CSP can have four basic characteristic forms: rigid base, flexible base, lead frame base and wafer scale.
CSP technology can replace SOIC and QFP devices and become the mainstream component technology.
One problem with the CSP assembly process is that the bonding pad for the interconnection is very small.Normally, the size of the bonding disc of the 0.5-mm spacing CSP is 0.250 ~ 0.275mm.With such a small size, printing solder paste through an opening with an area of 0.6 or less is difficult.However, with a well-designed process, printing can be done successfully.
The failure is usually due to insufficient solder due to blockage of the template openings.Board level reliability mainly depends on encapsulation type, compared to the CSP devices can withstand the heat cycle of - 40 ~ 125 ℃ of 800 ~ 1200 times, you can need not fill.However, the thermal reliability of most CSP increases by 300% if the filling material is used.The fault of CSP device is related to solder fatigue cracking.Another emerging field of passive component progress is 0201 passive component technology. Due to the market demand of reducing board size, people pay great attention to 0201 components.Since the 0201 component was introduced in mid-1999, cellular phone manufacturers have assembled them into phones with CSP, reducing the size of the board by at least half.This type of packaging is cumbersome, and optimization of pad size and element spacing are key to reducing the appearance of post-process defects such as bridging and upright.As long as the design is reasonable, the packages can be placed close to each other and the spacing can be as small as 150?M.
In addition, the 0201 device can be attached under BGA and large CSP.