A composite is made by combining two or more different materials together. The resulting combination has better properties than the individual materials used to make it. This allows the strength or durability of a product to be enhanced depending on the particular properties required. The article describes how a composite material, in this case a printed circuit board (PCB), can be characterized by thermal analysis.
Introduction
Thermal analysis comprises several different techniques that are used to measure the physical properties of a material as a function of time while the material is subjected to a controlled temperature program. The techniques include DSC, TGA, TMA and DMA. Thermal analysis is used in research and development, process optimization, quality control, damage and failure analysis as well as for investigating competitive products. The techniques allow the curing behavior of products, the compatibility of composite materials and the frequency dependence of the glass transition to be investigated [1].
Composites
A composite consists of two or more different materials. The properties of the new material are different to those of the individual materials. The individual materials used to make the composite remain distinct and do not mix with one other.
The purpose of making a composite can, for example, be:
- to improve mechanical properties (tensile strength, strain at failure, impact resistance)
- to change the color (through pigments)
- to improve flame resistance (of flammable binders)
- to stabilize (improve weather resistance)
- to aid processing (to make the polymer lighter and easier to process).
Composite materials can be classified according to their geometrical form. Besides the commonly used particle composites or fiber composites in which particles or fibers are embedded in a matrix (e.g. printed circuit boards, PCBs), there are laminate or multilayer composites and infiltration composites (foamed ceramics: a porous substrate filled with a binder).
Composites can also be classified according to the types of material used. This distinguishes between ceramic, organic or mineral particles or fibers as the reinforcement, and polymers, glass, metal or ceramics as the matrix.
Good examples of fiber-reinforced composites are carbon-fiber-reinforced polymers or plastics (CFRP). In recent years, these have become more and more important for products that need to be stiff but at the same time should have low weight, such as walking sticks, bicycle frames or boats. The fillers often used for composites are chalk (calcium carbonate), talc (magnesium silicate) or carbon black.
The most well-known composites include colored materials, polypropylene filled with chalk or glass fibers, or ABS (acrylonitrile-butadiene-styrene), PC (polycarbonate) and PP with flame retardants [2].
This article describes how a printed circuit board can be characterized.
Thermal analysis of composites | Thermal Analysis Application No. UC 562 | Application published in METTLER TOLEDO Thermal Analysis UserCom 56
