Original 45nm Intel® Core™ Microarchitecture

The Technical Challenges of Transitioning Intel® PRO/Wireless Solutions to a Half-Mini Card

REQUIRED PCB TECHNOLOGY

The PCB technology typically used for Mini Card designs is a lower-cost, standard through-hole via (THV) design, comparable to an industry-standard IPC Type 3 PCB. This was possible for two main reasons. The first is that there are no components on the bottom side of the Mini Card designs for the THVs to come in contact with. The second is that we were able to design the component packaging to not require any high-density interconnect (HDI) PCB technology. When we transitioned to a Half-Mini Card we were very limited on PCB area for components, so we had to utilize the bottom side of the PCB for components. The density of the components on both sides left us no room to place the THVs we had used on the Mini Card designs. This forced us to transition to HDI PCB technology. We needed a way to connect the I O between components without taking up the valuable component real-estate on the outer layers with THVs. Rather than using THV technology to solve the real-estate issues, we used HDI PCB technology in the form of a microvia and buried via technology. Microvias are about half the diameter of the previous THV technology. We could also utilize them in component pads to eliminate any real-estate lost from I O connection and routing on the outer layers. This is comparable to the industry standard IPC Type 4 and Type II PCB 2,3 . The two types of PCB structures are featured in (Figure 6) , where the differences can be clearly seen.

Figure 6: The PCB structure change between Full-Mini Card and Half-Mini Card

Though the new Half-Mini Card PCB size was almost half the size of our previous Mini-Card designs, our overall PCB cost was increased by the PCB technology transition. The cost increase came from several areas. The layer count was increased: extra PCB processing time was required for the sequential lamination process for the microvia and buried vias. There was an increase in added drilling steps from one THV mechanical drill step to four drill steps, that is, two laser drills and two mechanical drills. All these changes to the processing of the PCB for Half-Mini Card outweighed the savings of the smaller PCB size. However, we did not change the component packaging technology to utilize the HDI PCB technology. We did this so that our Mini Card and Half-Mini Card design could use the same components. This made it more challenging for the component packaging development, but it kept our cost down for the Mini Card PCB version by not having to transition it to HDI PCB technology.

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