Nowadays, the development of mobile phones is becoming more intelligent while mobile phone products become slimmer and more light-weight. This suggests that the internal components in mobile phones must be downsized further or integrated. As a result of this trend, both the flexible printed circuit (FPC) and substrate-like PCB (SLP) have to be promoted and applied more extensively.

 

Impact analysis
    To meet the trend of the thinner line in mobile phones, the HDI circuit process must be changed from the subtractive method to the modified-semi-additive process (mSAP) or the advanced modified-semi-additive process (amSAP) with a thinner CCL of copper thickness <3μm and 1μm to achieve the purpose of a finer line in mobile phones. Although Apple and Samsung are currently the only companies using SLP in smartphones, many PCB manufacturers predict that it is an inevitable trend for the line width/line space of mobile phone PCBs to move towards 15μm ~ 20μm and that other mobile devices such as smart watches may also have the potential to undergo this application. As a result of this, PCB manufacturers are willing to take the risk of investing in new equipment to build the mSAP line.

 

    HDI’s technological development and market applications have also been encouraged further. For example, from a technical development perspective, finer line mobile phones will need a more critical mSAP process and a smaller μVia aperture (<50μm) will be required. The Pico Second or Femto Second laser-drilling machine has to be used to reduce the thermal effect area. The aperture ratio must also reach about 0.8~1 and the coordinated Fan Out Wafer Lever Package circuit boards must have very low warping requirements, and so on. All these processes rely on the manufacturers’ investments in the resources from the material and equipment ends.

 

    From the market perspective, smartphones seem to currently have the most extensive applications but there are also potential applications for other portable devices such as smart watches. Within the current industry competition, the China-based PCB factories have gradually entered the HDI market, although their capacities and technologies are still behind that of Taiwan, Japan, Europe, and the United States. This has also inevitably forced the leading manufacturers to invest in advanced SLP product layouts, which is naturally also Apple’s actual demand, to avoid price competitions. Although there are currently not many SLP applications, when more SLP technologies and production capacities are set in place, more SLP applications will be encouraged as a consequence. In other words, the initial state of demand driving the SLP supply will possibly present a scenario of supply stimulating demand in the future.