Solder-Mounted Board Dual Insulating Layer Design
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Solution Overview
Problem
High-density component mounting on solder-mounted boards leads to issues such as reduced solder resist opening pitch, deformation, cracking, and insufficient underfill resin distribution, resulting in poor mounting reliability and connection failures.
Innovation Solution
A solder-mounted board design featuring a substrate with a wiring layer and solder pads, covered by a first and second insulating layer, where the solder pads are exposed through openings in the first insulating layer, and the component mounting region is within an opening in the second insulating layer, preventing underfill resin flow and ensuring reliable component mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pitch of openings in the solder resist is reduced for high-density mounting, then the component density increases, but the cream solder falls off and mounting reliability deteriorates
Solution Approach 1:
The solder resist structure is segmented into a first insulating layer and a second insulating layer, each with openings at different locations. This segmentation allows the solder resist to maintain structural integrity while accommodating high-density component mounting, preventing solder drop-off that occurs in conventional single-layer designs.
Solution Approach 2:
The invention transitions from a conventional single-layer solder resist to a two-layer insulating structure. The first insulating layer has openings for solder pad exposure, while the second insulating layer has a larger opening for component mounting region exposure, creating a multi-dimensional structural solution that resolves the contradiction between density and reliability.
2Ease of operation
If the opening aspect ratio of the solder resist is increased, then the component mounting is facilitated, but the solder flows upward during reflowing and mounting reliability deteriorates
Solution Approach 1:
The solder resist is divided into two functional layers: the first insulating layer with controlled openings for solder exposure, and the second insulating layer with a larger opening for component access. This segmentation prevents solder upward flow while maintaining ease of component mounting.
Solution Approach 2:
Different regions of the insulating structure have different opening characteristics optimized for their specific functions. The first insulating layer has smaller openings to prevent solder flow, while the second insulating layer has a larger opening to facilitate component mounting, achieving local optimization of both reliability and ease of operation.
3Quantity of substance
If the size of openings in the solder resist is reduced for high-density mounting, then the component pitch is reduced, but the solder resist deforms and cracks after component mounting
Solution Approach 1:
The solder resist structure is divided into two layers with different opening sizes and functions. The first insulating layer has smaller openings for high-density solder pad exposure, while the second insulating layer has a larger opening that provides structural support and prevents deformation and cracking during component mounting.
Solution Approach 2:
The invention uses a composite insulating structure consisting of two layers with different properties and functions. This composite structure maintains the mechanical strength needed to prevent cracking while enabling the small opening sizes required for high-density component mounting.
4Stability of the object's composition
If the elastic modulus of the solder resist is reduced to prevent deformation, then the solder resist flexibility increases, but migration occurs between wiring layers
Solution Approach 1:
The solder resist is segmented into two layers, allowing the first insulating layer to provide structural stability with appropriate elastic modulus to prevent wiring layer migration, while the second insulating layer provides the necessary flexibility and prevents overall deformation of the structure.
5Reliability
If the underfill resin is charged between the component and board, then the connection reliability is improved, but the underfill resin flows outside the component and charging becomes insufficient
Solution Approach 1:
The second insulating layer is configured with an opening that exposes the component mounting region before underfill resin charging. This preliminary configuration of the insulating layer structure guides and contains the underfill resin flow, ensuring proper distribution between the component and board while preventing overflow outside the component area.
Data Source
AI summary
The present invention provides a solder-mounted board which realizes reliable mounting of a component thereon; a method for producing the board; and a semiconductor device. The solder-mounted board includes a substrate; a wiring layer; a solder pad for mounting a component by the mediation of the solder; and an insulating layer which covers the wiring layer such that at least the solder pad is exposed, the wiring layer, the solder pad, and the insulating layer being provided on at least one surface of the substrate, wherein the insulating layer is formed of a first insulating layer provided on the substrate and the wiring layer, and a second insulating layer provided on at least a portion of the first insulating layer.