FaradFlex™ is an ultra-thin, high performance “family” of laminates used for low impedance, low inductance, and/ or embedded capacitance in printed circuit boards, chip package substrates, modules, and other electronic applications.
The material components of FaradFlex™ have properties which make the laminate unique at providing low impedance, high capacitance, and high reliability at substrate thicknesses of 1.0 mil (25 micron) down to as thin as 0.12 mil (3 micron). FaradFlex™ typically is used as a layer or layers in a printed circuit board. Most often the FaradFlex™ layers are designed as “paired” power/ ground layers which allow it to act as a capacitor. For optimum benefit and lowest impedance, FaradFlex™ is designed into a stack up close to the top and bottom layers of the PCB. For embedded capacitance, via hole connections are placed in the PCB down to the FaradFlex™ layer connecting to the active IC’s and eliminating the need to for most or all the 0.1 µf or 0.01 µf bypass capacitors. This also eliminates the need for the bypass capacitor pads, traces, and vias. FaradFlex™ can be used to significantly reduce the overall thickness of the PCB which can be a major design benefit.
The most common beneficiaries of FaradFlex™ are OEMs designing PCBs, modules, and chip packaging substrates. Although the OEM designers do not typically purchase PCB materials, they do determine the benefits and decide on the PCB requirements for EMI, signal integrity, power integrity, size, weight, reliability, lead free, “green”, and performance. FaradFlex™ allows the designer to achieve superior benefits for the above requirements that cannot be achieved using other materials and methodologies. Finally, the designer typically will work with a PCB fabricator/ purchaser to use FaradFlex™ in the designer’s PCB.
FaradFlex™ solves many PCB, chip packaging, and module performance issues. Common solutions using FaradFlex™ include:
- Eliminate resonance/ noise/ EMI from difficult PCB, modules, and module devices.
- Remove bypass capacitors from a dense and crowded PCB. Along with the capacitor removal, also removing 2 traces, pads, and via holes for each device. This allows room for other devices and new functionality. Also, it allows the PCB to be reduced in layers or dimensions if needed.
- Provide much improved power delivery by greatly reducing the inductance loop to an absolute minimum.
- Improve signal and power integrity.
- Improve reliability due to the elimination of many small capacitors and solder joints. The polymer film in most of the FaradFlex™ constructions is more robust to CAF as well as dielectric breakdown.
- Lower cost for the system and even the PCB. Although the laminate may have a higher cost than typical FR-4 laminates, using FaradFlex™ in many cases allows the PCB to be reduced in size or layer count. This can provide more PCB’s per panel at the fabricator. Additionally, there is a savings associated with eliminating the discrete capacitors and corresponding assembly.
- Allows for thinner PCBs or additional layers to be incorporated with little or no impact on overall thickness. Plating yields can be improved by reducing the aspect ratio, as well as letting existing connectors be used while increasing layer count.
Since every design is custom there is no clear rule to determine the exact amount of capacitors that can be removed. There is significant data that shows the amount of capacitance needed in the FaradFlex™ laminate can be as little as 1% or less than the amount that can be removed by eliminating the capacitors from the surface. This is primarily due to the fact that the thin FaradFlex™ laminate has magnitudes less impedance and a very small inductance loop for power delivery. Also, at frequencies above 200 MHz the surface capacitors do not have time to deliver their charge in many cases they are acting mostly as inductors rather than capacitors. There are case studies showing hundreds and even thousands of bypass capacitors coming off one PCB.
Since every design is custom there is no clear rule to determine the exact cost of using FaradFlex™. It is true that FaradFlex™ typically costs more that standard FR-4 materials used in PCBs. Even so, there are many tools available today showing how the technical, performance, and design benefits allow the PCBA and in many cases the PCB to cost less! We at Oak Mitsui Technologies encourage you to contact us to help determine what your cost impact will be.
FaradFlex™ has passed most or all of the electronics industry and IPC thermal reliability tests including those at “lead-free” conditions. FaradFlex™ is also much more robust to thermal stresses than typical high temperature, high Tg phenolic cured FR-4 materials used in PCBs.
Since FaradFlex™ is typically processed as a power-ground layer, it is normally very rigid in conveyor processing and inner layer processes and performs the same as other PCB materials. Since there is no fiber glass cloth to damage and a flexible epoxy, the FaradFlex™ MC24 laminate actually has better yields than FR-4. In other cases, the thinner FaradFlex™ laminates may be processed by attaching a rigid leader or frame to allow easy transport in the inner layer conveyors. Typically, this is one of the few or only process changes necessary and the cost is minimal.
So far, FaradFlex™ is compatible with all of the most common commercially available FR-4 materials. Also, there are many applications using ISOLA, NELCO, PANASONIC and other high performance materials. There are also current studies evaluating the compatibility and benefits of using FaradFlex™ with materials from Rogers, Taconic, Arlon and others.