Flexible Printed Board Restraining Space Surface Flashover
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Solution Overview
Problem
Existing flexible printed board connection structures are prone to surface flashover due to excessive outflow of conductive adhesive, particularly at the end portions of connection electrodes, leading to unintended electrical discharges.
Innovation Solution
A flexible printed board design incorporating a restraining space between the outermost terminals, combined with insulating layers and projecting portions, and dummy terminals to prevent surface flashover, utilizing an anisotropic conductive adhesive layer with conductive particles for electrical connection while maintaining insulation between adjacent terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If anisotropic conductive adhesive is used to connect flexible printed boards, then electrical connection between terminals is achieved, but surface flashover occurs due to excessive adhesive outflow at end portions
Solution Approach 1:
The connection structure is divided into distinct functional zones: a connection region with terminals and wiring lines, and a restraining space with insulating structures. This segmentation isolates the conductive adhesive to specific areas where it is needed, preventing unwanted outflow and surface flashover while maintaining reliable electrical connections at the terminals.
Solution Approach 2:
An insulating layer is introduced as an intermediary element between the conductive adhesive and the external environment. This insulating layer acts as a barrier that contains the adhesive within the connection region, blocking its path to the edge portions where surface flashover would occur, thus preventing harmful electrical discharge while preserving connection functionality.
2Area of stationary object
If connection electrodes are placed close to edge portions for compact design, then board size is reduced, but surface flashover risk increases due to adhesive outflow to edge portions
Solution Approach 1:
The solution extends the protection into the thickness dimension by introducing an insulating layer that protrudes from the front surface toward the rear surface. This three-dimensional insulating structure creates a vertical barrier that blocks adhesive outflow in the thickness direction, preventing surface flashover even when terminals are positioned close to edge portions for compact design.
Solution Approach 2:
The insulating layer is formed in advance during the manufacturing process, creating a pre-established barrier structure before the conductive adhesive is applied. This preliminary insulating structure proactively prevents adhesive outflow and surface flashover, allowing terminals to be positioned closer to edges without increasing flashover risk.
3Reliability
If restraining space is provided from outermost terminals through edge portion, then surface flashover is prevented, but manufacturing complexity increases
Solution Approach 1:
The insulating layer serves multiple functions simultaneously: it provides electrical insulation between wiring lines, acts as a barrier to contain conductive adhesive, and creates the restraining space effect to prevent surface flashover. This multi-functionality achieves reliable surface flashover prevention without significantly increasing manufacturing complexity, as the same insulating structure fulfills multiple protective roles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively restrains surface flashover by containing the anisotropic conductive adhesive and preventing electrical short-circuits, even under high voltage conditions, while allowing for efficient electrical connectivity.
Implementation Method 1
an anisotropic conductive adhesive layer (4) is superposed in a stretching manner on a region including the connection electrodes (9a, 10a, 15a, 16a)... conductive particles are caught between connection wiring lines (3a) of the connection member (1) and the connection electrodes (9a, 10a, 15a, 16a), so that each connection wiring line and each connection electrode are caused to be electrically connected in the thickness direction
Data Source
AI summary
Provided is a flexible printed board including: an insulating base material; a plurality of first wiring lines disposed on a front surface side of the base material; a plurality of first terminals each provided on an external connection side, of a respective one of the plurality of first wiring lines; a plurality of second wiring lines disposed on a rear surface side of the base material; and a plurality of second terminals each provided on an external connection side, of a respective one of the plurality of second wiring lines; in which: a restraining space for restraining surface flashover is provided from a first outermost terminal, which is outermost of the plurality of first terminals, through an edge portion of the base material, to a second outermost terminal, which is outermost of the plurality of second terminals.