In recent years, tablet and smart phone have been expanding rapidly in the market with high popularity.With the public's demand for high function, high-density packaging technology is also being pursued. In order to achieve high function and high density, it can be expected that the size of CSP will become thinner and larger. Relatively, new technologies and new materials such as 3D packaging and large wl-csp are also expected.In response to these requests, the qianzhu metal industry has prepared a number of welding materials for different purposes and USES, to be published in SEMITaiwan.
The so-called 3 d packaging, is the PKG and electronic components, upward joint in longitudinal way, substrates and parts will be nearly 250 ° C to soldering furnace as many back and forth.As a result of the solder melt and overloading, it is possible to cause an electrical short circuit between solder and solder.In view of this subject, chi-ju metal has proposed a copper core ball which can really ensure space.Copper bronze as core nuclear ball, ball, its melting point temperature is about 1080 ° C, namely in the flux of back to back and forth, copper ball shape will not change, so keep a certain space for 3 d packaging.In addition, the copper column, which must be used in common electroplating engineering, can be changed into copper core ball, which can be encapsulated with existing equipment.
With high functionality and high density packaging, Chip sizes tend to be thinner and larger.The difference in the thermal expansion coefficient between the base plate and the Si with low thermal expansion coefficient will cause the electrode and the solder ball to touch each other, which may cause damage or even damage.The M758 was developed as a solution to this problem by the qianzhu metal industry.
The M758 adds sn-3ag-cu series with Bi and Ni, which is further strengthened through solid solution strengthening and precipitation strengthening, and further strengthens its structure. The base plate and Chip are more solid, and its characteristic of heat resistance and fatigue is the most suitable solder ball material for WLCSP.
Due to the characteristics of the mobile device, it is required to be resistant to falling impact and the increased battery area. In the loop part, high-density packaging is required to increase the heat-resistant fatigue characteristics of peripheral parts.To meet the above requirements, we have developed a solder ball M770 which has both resistance to thermal fatigue and impact resistance.
In general, the cleavage due to thermal fatigue is caused by solder expansion, while the cleavage due to falling impact properties is generated by solder on the boundary between solder and PKG.The pursuit of fatigue resistance reduces its impact resistance and vice versa.If you want to have heat resistance fatigue and drop impact resistance at the same time, its approach methods are each other, it is very difficult to take the countermeasures.
To solve this problem, the content of Ag can be adjusted to the softness of solder solder, and the adjustment of Ag content is suitable for fatigue resistance.Generally, in the case of surface treatment of PKG, Sn, the main component of Cu, Ni and solder without lead, is very easy to react, thus producing a rather thick alloy layer.When the M770 is hit by falling, it can mitigate the impact of solder on the interface between the solder and base plate to prevent the crack formation.In thermal shock tests, the possibility of cracking when solder is expanded is also reduced.
Based on the requirement of multifunctional, not only the size required by PKG is small and space saving, but also the non-washing products are required in the pursuit of the small Chip of solder ball packaging. Therefore, it is very important in the choice of flux.Qianzhu metal has developed the series of DELTALUXFLUX901K, which has excellent wettability, low volatility and cleaning property, as well as the series of DELTALUXFLUX901K, which need not be cleaned after encapsulation, and the JointProtectFluxJPK8, which is used as joint solder residues, and has good compatibility with Underfill.