Prepreg, also known as pre impregnated material or bond sheet, it’s the main laminating material used in multilayer printed boards manufacturer. It is a type of thin sheet material made up of resins and reinforced. Reinforcement materials can be divided into glass cloth and other composite materials. Resins include epoxy resin, polyimide, cyanate ester and BT resin.
Prepreg is the solidified state of resin sheet.because the resin is an organic polymer material. In the process of production, the curing state of the resin is usually divided into three stages of A.B and C.
The A phase is a liquid resin that can flow completely at room temperature.
The B phase is partially cross linked with epoxy resin in semi curing state, and it can be restored to liquid state under heating conditions.
The C phase is all the crosslinking of the resin, which softens under heating and pressure, but can not become a liquid again. This is the final state of the transformation of prepreg sheet after the press of the multilayer printed board.
Prepreg is a pre impregnating material that solidified the resin into the B stage.
The prepreg used for laminating laminate should be the same or compatible with the thin base material used. For example, the use of the common FR4 base material should adopt the FR4 prepreg sheet, and the glass transition temperature (Tg) should be the same, which is beneficial to the process control and the quality of the product.
At present, most of the prepreg used in Multilayer PCB manufacture is glass cloth as reinforcing material. Therefore, the following will mainly discuss glass cloth reinforced prepreg.
The glass cloth reinforced prepreg sheet is a thin material made of resin bonded fabric, impregnated with resin liquid, and then prebaked to make the resin into the B stage. In order to improve the binding force between the glass cloth and the resin, a special coupling agent is applied to surface treatment on the surface of the glass cloth used in prepreg sheet after degreasing. It is usually possible to purchase prepreg directly in the market without self – preparation.
The length direction of the glass cloth is called radial, and the warp knitting yarn is called “warp”. The direction perpendicular to the warp is zonal, and the corresponding yarn is called “weft”. The number of units per warp and weft in different kinds of glass cloth is different. Therefore, prepreg types have 106, 1080, 2112, 2113, 2116, 2165, 1500, 7628 and other specifications according to the thickness of the yarn. The corresponding thickness of each glass cloth is different after lamination.