Issue link: https://iconnect007.uberflip.com/i/978458
34 PCB007 MAGAZINE I MAY 2018 Panel sizes The material cost of making a PCB covers approximately 30% of the total value, so us- ing a panel size that best fits the master sheet is essential. Then the PCB size becomes even more interesting because the process cost of making a panel can be set to one, and the in- dividual price is then 1/n depending on how many PCBs you can fit on that panel. Smaller features As the density of the pattern gets higher and higher, the understanding of the copper thick- ness required for the different layers sets the limitations for miniaturization of the board. Also, the different materials' electrical proper- ties make it possible to shrink the pattern. Large format is key in 5G, especially for the lower frequencies where active antenna boards for beam forming can be as large as up to 800 mm (31.5 in.), which requires an even larger panel to be able to be produced. Faster speeds Serial links today go up to 28Gbit/s, but next generation mobile systems will require up to 56 Gbit/s so the individual selection of glass and copper foil properties is vital to success. Warmer Power consumption is essential to the per- formance and it makes the PCB warmer both as a heat source in components but also on an- tennas where some patterns get hot (>100°C). The material's behavior of not breaking down and changing its losses over time is important for a reliable product to prevent it from catch- ing fire. Environmental Avoiding hazardous substances is impor- tant; using halogen-free materials where pos- sible and choosing the halogen-free alternative when it's technically and commercially avail- able is important. PCB Material Needs It is also important to share our current and future material needs to both the PCB suppli- ers and the laminate producers to be able to look for new cost-effective alternatives or in- creased performance. It is and will be important to know all the material properties: • Dk and Df – Dk and Df values over frequency (1, 2, 5, 10, 15, 30 GHz) – Dk and Df values over temperature (-40°C, +20°C, +100°C) – Measurement methods (e.g., IPC-TM-650 2.5.5.5, SPP, SPC, etc.) • Copper surface roughness – Ra, Rz and Rq/RMS • Mechanical properties of material – Flexural modulus – Flexural strength – Over temperature (-40°C, +20°C, +100°C) • Break down voltage/dielectric strength Current Requirements that do not specify the PCB laminate names but rather the properties at certain conditions make the material suppliers aware of what we use today and in the future. Table 3 shows current halogen-free PCB mate- rial needs. The future requirements are for materials with Dk of 3.5 and 3.0 that are also halogen- free and fully capable for making multilayers. However, for microwave designs a Dk of 1.0 (air) is preferable. It is also important that the material keeps its properties over frequency and temperature ranges of 1−30 GHz and from -40°C to +100°C, respectively. Table 4 shows future halogen-free PCB material needs. Resin Development You must start to collaborate with the PCB material suppliers on resin development and share your current and future requirements so these can be considered during the resin for- mulation steps. Today, developing a material in the range of a MEGTRON 6 or TerraGreen could take up to five years until it is commer- cially available to the market, especially if we add the PCB manufacturers' process learning curve and future UL approvals before we can start to use it in products.