Flexible Printed Wiring Board Layout for Solder Heat Isolation
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Solution Overview
Problem
Existing flexible printed wiring boards (FPCs) experience quality degradation due to heat transmission during soldering, leading to air bubbles in the adhesive layer and detachment of cover films.
Innovation Solution
The flexible printed wiring board configuration includes a base film with a first conductor layer on one surface and a second conductor layer on the other, connected via a through-hole, which reduces heat transmission by increasing thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soldering is performed on the exposed portion of the conductor layer to electrically connect wirings, then electrical connection between components is achieved, but heat is transmitted to the adhesive layer and cover film causing air bubbles and detachment
Solution Approach 1:
The conductor layer is divided into two separate layers: a first conductor layer for signal transmission and a second conductor layer for soldering connections. This segmentation allows the soldering heat to be confined to the second conductor layer while the first conductor layer remains thermally isolated, preventing heat-induced damage to the adhesive layer and cover film while maintaining electrical connection functionality.
Solution Approach 2:
The base film serves as a thermal barrier and intermediary between the first and second conductor layers. It physically separates the two conductor layers and prevents direct thermal conduction from the soldering zone to the adhesive layer, acting as a heat-blocking mediator that protects sensitive regions during the soldering process.
2Ease of manufacture
If the conductor layer is made thick to improve solderability, then soldering becomes easier, but heat conduction increases causing more severe quality degradation
Solution Approach 1:
The conductor layer is segmented into two distinct layers with different thicknesses and functions. The second conductor layer has sufficient thickness for good solderability, while the first conductor layer maintains appropriate thickness for signal transmission. This segmentation allows each layer to be optimized independently, achieving both ease of manufacture and reduced heat conduction.
Solution Approach 2:
Different regions of the conductor system have different thicknesses and properties tailored to their specific functions. The second conductor layer at the soldering interface has optimized thickness for solderability, while the first conductor layer has thickness optimized for electrical signal transmission. This local quality differentiation ensures solderability without excessive heat conduction.
3Length of moving object
If multiple FPCs are connected to form long electric wiring, then wiring length requirement is met, but the number of soldering connections increases leading to cumulative heat damage
Solution Approach 1:
Each FPC module is segmented with its own first and second conductor layers, allowing independent optimization of each connection point. The standardized two-layer conductor structure enables modular assembly where each soldering joint is thermally isolated, preventing cumulative heat damage even when multiple FPCs are connected in series to achieve long wiring lengths.
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
This configuration effectively reduces quality degradation by minimizing heat transfer to the first conductor layer, thereby preventing air bubbles and detachment issues during soldering.
Implementation Method 1
the through-hole is provided so as to penetrate the base film and electrically connect the first conductor layer and the second conductor layer to each other... reduces heat transmission by increasing thermal resistance
Implementation Method 2
the second conductor layer has a solderable region... The exposed portion of the conductor layer 520 of the left FPC 500A is bonded. Subsequently, the bonded portion is heated with sandwiched from both sides by a first heating tool 610 and a second heating tool 620... the solder S in the paste form is melted
Implementation Method 3
Heat generated during the soldering process is transmitted from the solder S in a direction of separating from the solder S portion particularly via the conductor layer 520 having a high thermal conductivity
Data Source
AI summary
Provided is a flexible printed wiring board including: a base film which is an insulating layer; a first conductor layer; a second conductor layer; and a through-hole, in which the first conductor layer is provided on one surface of the base film, the second conductor layer is provided on the other surface of the base film, and the through-hole is provided so as to penetrate the base film and electrically connect the first conductor layer and the second conductor layer to each other, and the second conductor layer has a solderable region.