Printed Wiring Board Nickel Plating Adhesion Reflow Foaming
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Solution Overview
Problem
Printed wiring boards with metal reinforcing plates experience reduced adhesion force and conductivity issues during the reflow step, leading to foaming and peeling, which compromises the quality of the board's electrical connections.
Innovation Solution
A printed wiring board with a conductive adhesive layer containing a nickel layer having a surface area ratio of nickel hydroxide to nickel between 3 and 20, enhancing adhesion and conductivity by improving intermolecular forces and hydrogen bonding, and using a nickel sulfamate bath for plating to ensure strong bonding between the nickel layer and the adhesive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the metal reinforcing plate is nickel plated to improve conductivity and eliminate electromagnetic waves, then the conductivity and electromagnetic shielding are improved, but the adhesion force between the conductive adhesive layer and the nickel plating layer is compromised
Solution Approach 1:
The invention changes the surface chemical composition parameters of the nickel plating layer by controlling the ratio of nickel hydroxide to nickel to be within 1.8 to 3.0, which optimizes both conductivity and adhesion properties
Solution Approach 2:
The invention creates a composite surface structure on the nickel plating layer consisting of nickel and nickel hydroxide in specific proportions, combining the benefits of both materials for improved adhesion while maintaining conductivity
2Strength
If the adhesion force is improved by controlling nickel hydroxide ratio, then the bonding strength is improved, but foaming occurs during the reflow step causing peeling
Solution Approach 1:
The invention precisely controls the nickel hydroxide to nickel ratio within 1.8 to 3.0 and adjusts the water contact angle to 50-100 degrees, which prevents foaming during reflow while maintaining adhesion strength
Solution Approach 2:
The invention prepares the nickel plating layer surface in advance with controlled nickel hydroxide formation and specific water contact angle properties, which prevents foaming and peeling from occurring during the subsequent reflow process
3Strength
If the nickel plating layer is made smoother to improve adhesion, then the bonding is improved, but the surface area ratio of nickel hydroxide to nickel is reduced affecting adhesion quality
Solution Approach 1:
The invention establishes a dual-parameter control system that simultaneously manages the nickel hydroxide to nickel surface area ratio (1.8-3.0) and water contact angle (50-100 degrees), achieving both adhesion quality and manufacturing precision
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
The solution effectively prevents air bubbles and maintains excellent adhesion and conductivity even after the reflow step, ensuring reliable electrical connections and improved durability of the printed wiring board.
Implementation Method 1
a ratio of a surface area of nickel hydroxide to nickel present in a surface of the nickel layer is more than 3 and equal to or less than 20
Implementation Method 2
The conductive adhesive layer includes a hydroxyl group
Data Source
AI summary
An object of the invention is to provide a printed wiring board which is less likely to cause foaming even after a reflow step and in which a metal reinforcing plate is less likely to be peeled off, a manufacturing method thereof, and an electronic device. A printed wiring board (1) according to the present invention includes a wiring circuit board (6), a conductive adhesive layer (3), and a metal reinforcing plate (2). The conductive adhesive layer (3) is bonded to each of the wiring circuit board (6) and the metal reinforcing plate (2). The metal reinforcing plate (2) includes a nickel layer (2b) formed on a surface of a metal plate (2a). A ratio of a surface area of nickel hydroxide to nickel present in a surface of the nickel layer (2b) is more than 3 and equal to or less than 20.