What is FR-4 PCB material?
We've all heard the abbreviation FR4 being tossed about at some point when buying a PCB fab house, but what does it in fact suggest? And what ramifications does it have when choosing a PCB material? This post will help clear the fog and introduce some popular materials available for rigid PCBs.
Probably, you will have seen FR4 as the standard option for small batch or prototype PCBs like in Speed Fusion. FR-4 refers to a grade of material rather than a material itself and has many sub gradings and types such as TG130, High TG, FR4-Rogers. The FR4 choice on the PCB order page is the grade designation for the epoxy fiberglass that frequently forms the PCB core and prepreg layers. It is the residential or commercial properties of this base that provides the PCB the electrical seclusion and mechanical strength needed to withstand progressively requiring applications.
In a common PCB, the core offers the rigidness and the foundation on which the PCB traces can be 'printed' onto. In addition, the FR4 core and laminates form the electrical isolation separating copper layers. For double layer boards, an FR4 core separates the leading and bottom copper layers whereas, in multilayer PCBs, additional layers of FR4 prepreg are sandwiched between the inner core and the outer copper layers. The desired final thickness of the PCB can be controlled by including or removing specific laminates or utilizing laminates of various densities. Usually, a 1.6 mm board will have 8 layers of fiberglass sheets, if we desired a 0.8 mm board we can decrease the number of sheets to 4.
The name FR4 comes from the NEMU grading system where the 'FR' represents 'fire retardant', certified with the UL94V-0 requirement. You might have discovered that on the Speed Fusion order page the FR4 option is followed by TG130. The TG refers to the shift glass temperature level-- the temperature level at which the glass-reinforced material will begin to warp and soften. For Fusion's standard boards this value is 130 ° C, which is more than enough for the majority of applications. Unique High TG materials can stand up to temperature levels of 170-- here 180 ° C and can be purchased online using the Advanced PCB service.
FR4 laminates owe their flame resistance due to its bromine content, a non-reactive halogen commonly used in market for its flame slowing down residential or commercial properties. This provides FR4 materials obvious advantages as a stock PCB material, specifically in prototyping where circuits are still in the preliminary screening stages and might be pressed to extremes. If your soldering abilities are not up to standard, it is also a little assuring.
Other comparable grades utilized for PCBs include FR2, which is a type of fire retarding fiberglass resin bonded paper and G10 which is not flame resistant at all. FR2 is more affordable therefore has its uses in mass production of low-end electrical equipment. G10, a predecessor to FR4, has all however been taken over by the safer FR4 standard. Its only usage in PCBs now remains in designs that desire this combustible home.
This blog site has covered more information on stiff PCB materials than the typical hobbyist will ever need, however must you ever find the use for High TG or more customized materials, you can have a look at Speed Fusion Advanced PCB service for more choices including high-frequency boards and rigid-flex PCBs.
The FR4 choice on the PCB order page is the grade classification for the epoxy fiberglass that often forms the PCB core and prepreg layers. In a common PCB, the core supplies the rigidity and the foundation on which the PCB traces can be 'printed' onto. For double layer boards, an FR4 core separates the leading and bottom copper layers whereas, in multilayer PCBs, additional layers of FR4 prepreg are sandwiched between the inner core and the external copper layers. Typical thinner thicknesses are utilized in multilayer boards in which the FR4 board is utilized to distribute signals to other boards, in order to not increase the thickness of the PCB. Greater densities are utilized when high robustness of the PCB is required because a large PCB is developed.