To introduce a new technology in SMT welding, CSP technology, CSP technology has become the darling of SMT, its charm lies in its many advantages, such as reducing the package size, increasing the number of stitches, performance enhancement, etc. next, we will briefly introduce what is CSP.

As long as we focus on the themes of various professional conferences held in different places today, it's not difficult to understand the latest technologies used in electronic products. CSP, 0201 passive components, lead-free welding and Optoelectronics are the popular advanced technologies that many companies practice and actively evaluate on PCB recently. For example, how to deal with the problem of ultra small opening (250um) which is common in CSP and 0201 assembly is a basic physical problem that has never been existed before in solder paste printing.

Board level optoelectronic assembly, as a large field developed in communication and network technology, has a very fine technology. Typical packaging is expensive and easy to damage, especially after the device leads are formed. The design guidelines of these complex technologies are also quite different from those of ordinary SMT processes, because plate design plays a more important role in ensuring assembly productivity and product reliability. For example, for CSP welding interconnection, only by changing the size of the plate bonding plate, the reliability can be significantly improved.

CSP application

Nowadays, CSP is a common key technology. The charm of CSP technology lies in its many advantages, such as reducing the package size, increasing the number of stitches, enhancing the function / performance, and reworking the package. CSP has the advantages of high efficiency: when it is used in board level assembly, it can cross the boundary of peripheral package with fine spacing (as small as 0.075mm) and enter the area array structure with large spacing (1, 0.8, 0.75, 0.5, 0.4mm).

Many CSP devices have been used in the field of consumer telecommunications for many years. They are generally considered as low-cost solutions in SRAM and DRAM, medium pin ASIC, flash memory and microprocessor fields. There are four basic characteristics of CSP: rigid base, flexible base, lead frame base and wafer scale. CSP technology can replace SOIC and QFP devices and become the mainstream component technology.

There is a problem in CSP assembly process, that is, the bonding plate of welding interconnection is very small. Generally, the size of bonding plate with 0.5mm spacing CSP is 0.250-0.275mm. With such a small size, it is difficult to print solder paste through an opening with an area ratio of 0.6 or lower. However, printing can be successfully carried out by using a well-designed process. However, the failure is usually due to the lack of solder caused by the blocking of the opening of the template. The board level reliability mainly depends on the packaging type, while CSP devices can withstand 800-1200 thermal cycles at - 40-125 ℃ on average, and can be filled without any need. However, if the lower filling material is used, the thermal reliability of most CSPs increases by 300%. The failure of CSP devices is generally related to solder fatigue cracking.