Even though they often appear together, prepreg and core are distinct materials. They both have significant roles to play with one another but serve different purposes when building a circuit board. But these two components form the foundation of any PCB structure. You will find them present on most boards as each has its own role – while one provides insulation, the other offers structural support.
The Role of Prepreg in PCBs
Regarding PCB construction, prepreg is used predominantly as an insulator. This bonding material helps reinforce a board by providing dielectric insulation between the copper surface and inner core layers. As such, prepreg acts like a barrier keeping current from passing through these disparate elements. With its unique properties, prepreg offers reliable strength for large-scale projects and other demanding applications.
The application process for core materials is made easy with prepreg, which consists of fiberglass fabric covered in resin. This knitted fabric has a unique tissue-like structure – giving it superior adhesion capabilities when partially dried. To match customer expectations precisely, designers must take the time to assess and adjust the volume friction of prepreg before applying it.
The Purpose of Core in PCBs
At the core of all PCBs lies a resilient mixture known as FR-4, composed of titanium epoxy laminates and copper interwoven with fiberglass cloth to form a fire-resistant layer. Adding protective layers such as Prepreg Insulation or Copper foil to single-sided or double-sided boards can add strength without sacrificing weight. Most electronic manufacturing services offer multilayer PCBs that combine these two processes for maximum security.
What Sets Prepreg and Core Apart?
Fundamentally, prepreg and core layers are alike since they contain the same fundamentals to form a sturdy board that works together for extra support. Due to this similarity, many individuals confound them. However, their key distinction is easy to understand.
Difference #1: How PCBs Implement Core and Prepreg
The core, as the central layer of a PCB, serves to give boards extraordinary strength and stability. Then, when laminated with prepreg, this insulation layer acts as an additional barrier against electrical leakage between components and guards them against outside forces that could cause harm. All in all, these two layers meld together to form reliable structures for any design needs.
Difference #2: The Impact of Core and Prepreg Creation on Outcome Quality
The core is cast and cured as one rigid piece with singular intent. If the material remains challenging, it will make for an ideal support base in your PCB assembly process. On the other hand, prepreg can be altered at multiple points to modify its properties during production overall.
Unfortunately, it is challenging to accurately calculate the amount of impedance that needs connecting between your prepreg and core. Depending on how prepreg is mixed, some boards may have too much or too little resistance, which poses a risk. Unexpectedly high or low resistance levels can cause incompatibility between them, which is hard to predict in advance.
Prepreg and core are essentially the same yet different in specific key ways, making it essential for engineers to consider them carefully before implementation. One of their most significant advantages is that both components can provide insulation and strength and enable multi-layered board development.
source: https://www.myemssolutions.com/explaining-prepreg-and-core-in-pcb/
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