Wedge-Shaped Recess in Wiring Board Module for Solder Splash Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing module designs fail to prevent solder splashes due to moisture penetration and expansion, leading to gaps and short-circuits between components and wiring boards, despite efforts to enhance adhesion between sealing and solder resist layers.
Innovation Solution
A module with a recess substantially wedge-shaped in cross section at the boundary between the mounting electrode and photosensitive resin, filled with sealing resin, which improves adhesion and prevents moisture penetration, and a two-layer mounting electrode structure with a Cu surface layer and Ni/Au plating layer to enhance solder wettability and prevent oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the solder resist is partially removed and the exposed wiring board is covered with sealing resin layer, then the adhesion between sealing resin layer and wiring board is enhanced, but moisture can still penetrate into the interface between wiring board and sealing resin layer, creating gaps that lead to solder splashes
Solution Approach 1:
A resin layer is introduced as an intermediary between the sealing resin layer and the photosensitive resin. This intermediate resin layer fills the gaps and prevents moisture penetration, thereby preventing solder splashes while maintaining the enhanced adhesion benefit of the sealing resin layer.
2Object-affected harmful factors
If the sealing resin layer is applied to cover the photosensitive resin and component, then protection against moisture is provided, but expansion force from moisture vaporization creates gaps between the sealing resin layer and photosensitive resin, causing solder splashes
Solution Approach 1:
The intermediate resin layer acts as a mediator between the sealing resin layer and photosensitive resin, absorbing expansion forces and preventing gap formation. This eliminates the harmful effect of gap creation while maintaining moisture protection.
Solution Approach 2:
The coefficient of linear expansion of the intermediate resin layer is designed to be between that of the sealing resin layer and photosensitive resin. This parameter matching reduces thermal expansion differences and prevents interfacial peeling and gap formation during temperature cycling.
3Ease of manufacture
If a flat interface is used between sealing resin layer and photosensitive resin, then manufacturing is simple, but moisture penetration and expansion create gaps leading to solder splashes
Solution Approach 1:
The interface structure is extended from a flat two-dimensional surface to a three-dimensional configuration with the intermediate resin layer filling the gaps. This dimensional change prevents moisture penetration paths while maintaining manufacturing feasibility.
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 solder splashes by enhancing adhesion between the sealing resin and photosensitive resin layers, elongating the gap path to prevent solder flow and reducing the likelihood of short-circuits, while improving solder wettability and preventing oxidation of the surface electrode layer.
Implementation Method 1
provides an anchor effect, which improves an adhesion strength between the sealing resin layer and the photosensitive resin at the recess
Implementation Method 2
a two-layer mounting electrode structure with a Cu surface layer and Ni/Au plating layer to enhance solder wettability and prevent oxidation
Implementation Method 3
moisture penetrating into an interface between the solder resist and the sealing resin and into an interface between the solder resist and the wiring board turns to vapor
Implementation Method 4
The resulting expansion force of the vapor may create gaps in the interfaces
Implementation Method 5
the solder that connects the components and the wiring board is remelted by heat produced when the module is mounted on the motherboard
Data Source
AI summary
A module includes a wiring board; a plurality of mounting electrodes for component mounting, the mounting electrodes being disposed on one principal surface of the wiring board; a plurality of components mounted on the one principal surface of the wiring board and solder-connected to the mounting electrodes; a solder resist being a photosensitive resin configured to cover the one principal surface of the wiring board, with a plating electrode layer of each mounting electrode exposed; and a sealing resin layer disposed on the one principal surface of the wiring board, the sealing resin layer being configured to cover the photosensitive resin and the components connected to the mounting electrodes. A recess substantially wedge-shaped in cross section is provided at a boundary between the plating electrode layer of each mounting electrode and the solder resist, and the recess is filled with resin of the sealing resin layer.