In recent years, with the electronic products’fast developments to small, high-performance and multi-functionalization, multi-layer rigid-flex board, step board, cooling plate’s processing technology is rising. In order to prevent flowing glue in the rigid-flex joint、the step slot,etc., pure prepreg often be as a connecting materials,it is difficult to meet the requirement of the rigid-flex joint plate because of pure prepreg’s poor stability. As a result, many PCB manufacturers are looking for other alternative materials for bonding between rigid boards and flexible boards, and the currently preferred replacement material is a Non-Flow Prepreg.
It has bigger difference for Non-Flow Prepreg and ordinary FR-4,so we can not simply apply conventional FR-4’s processing experience. For example, since the Non-Flow prepregs often require opening windows operations, the Non-Flow prepregs must have good toughness and machinability. “Non-Flow” is the largest characteristics of Non-Flow prepreg,if using the ordinary FR-4 lamination conditions when laminate Non-Flow prepregs, because of small glue flow,it will appear white spots and other defects in the line spacing of the board or the surface filling capacity.
This paper combined with experimental verification,it is detailed analysis of the characteristics of Non-Flow prepreg,and provides numbers of recommendations for Non-Flow prepreg processing.

Demand Analysis of Non-Flow Pprepreg
The report pointed out that the demand of rigid-flex plate,step PCB board will increase year by year, as shown in Fig. 1.
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Fig 1 Demand change of rigid-flexible plate,step PCB board

Kinds of Non-Flow Pprepreg
At present,there are two kinds of common Non-Flow Prepreg: ordinary Tg and high Tg. When high Tg FR-4 material is used for step board or rigid-flex plate,high Tg Non-Flow prepregs are typically used for lamination. If the general plate has no Tg requirement, the ordinary Tg Non-Flow prepreg will be commonly used for lamination in the industry. If the board has halogen-free requirements, you need to use halogen-free Non-Flow prepreg to match and use.
A company in China has developed a high-performance Non-Flow prepreg(SP120N) in order to meet the needs of the fields such as step board and rigid-flex joint board. It has been gradually got the market recognition since it was entered into the market in 2007.

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pdfDiscussion on the features of No-Flow prepreg.pdf