Advanced packaging developed as a means of improving device performance while shrinking packages at the same time. Improvements continue along this track. To understand where we are today, let’s go back and look at what advanced packaging is.
The first mobile phones were a little under 23 millimeters thick. The sleek and stylish 10 mm phones of 2010 were only possible thanks to wafer level packaging (WLP) and PoP. Traditional packaging encapsulated each individual chip, requiring more weight in exchange for even more instability. WLP overcame this limitation by bonding protective layers onto the wafer before cutting it into separate chips. This way, chips could be tested before they were diced, and the manufacturing process functioned more smoothly.
WLP uses conductive bumps, which cover the semiconductor pad. They allow face-down bonding, which in turn enables a smaller package size. Most bumping material is made of metal solder, but lead free and high lead materials adapt it to different applications. Bumping improves both reliability and economy. Modern solder balls are larger than they once were and can be attached to the pads or transmitted from them. They don’t need extra equipment or underfilling, and WLP can be designed to incorporate extra device protection and testing.
Flip Chip Bonding
Flip chip bonding has advanced in recent years, allowing direct connection onto substrates. This way, the sluggishness of wire bonding is resolved, and electromagnetic emissions are reduced. The layout of the chip area is remarkably flexible, and heat transfer is improved dramatically.
Reliable fluxing is a core part of the process. It affects corrosion resistance and solder spreading, which are best achieved through dip fluxing and flux dispensing. Flip chip bonding results in a flawless soldering process, where precise adjustments of the soldered bump can be achieved. Redistribution of contact points is a highly innovative process, so it’s not uncommon for designs to be patented. Wafer level packaging is one of the most exciting solutions for high-end gadgets, allowing for an entirely new class of mobile technology.