Substrate Wetting Prevention Region for Solder Spread Control
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Solution Overview
Problem
Existing methods for manufacturing substrates with built-in components face issues of short circuits due to solder or conductive adhesive spread, especially in multilayer structures, where high temperature processing can cause solder flow and reliability problems, and the use of insulating layers leads to adhesion strength issues at material interfaces.
Innovation Solution
A method involving the formation of land regions and a wetting prevention region on a metal foil, where the wetting prevention region has inferior wettability to solder or conductive adhesive, allowing for controlled connection of circuit components and preventing solder or adhesive spread, eliminating the need for an insulating layer and reducing the risk of short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder or conductive adhesive is spread to electrically connect terminal electrodes to land regions, then electrical connection is achieved, but the solder or adhesive spreads in the primary surface direction causing short circuits between adjacent lands or wiring patterns
Solution Approach 1:
The invention applies different surface properties to different regions of the metal foil. The land regions are formed with a plating layer having high wettability to solder/conductive adhesive for good electrical connection, while the wetting prevention region surrounding the lands has low wettability to prevent solder/adhesive spread. This local differentiation of surface quality resolves the contradiction between achieving reliable electrical connection and preventing short circuits.
Solution Approach 2:
The wetting prevention region acts as an intermediary barrier between adjacent land regions. By having inferior wettability to solder and conductive adhesive, this intermediate region prevents the direct contact and spreading of solder/adhesive between lands, thereby preventing short circuits while allowing proper electrical connection at the land regions themselves.
2Object-affected harmful factors
If an insulating layer with opening portions is formed to prevent solder spread, then short circuit risk is reduced, but a relatively large amount of solder must be filled in the opening portions increasing solder flow risk
Solution Approach 1:
Instead of using an insulating layer with openings that requires filling large amounts of solder, the invention uses local quality differentiation on the metal foil surface itself. The land regions have high wettability to attract and hold minimal solder/conductive adhesive, while the surrounding wetting prevention region has low wettability to prevent spread. This eliminates the need for insulating layers and reduces solder quantity while maintaining prevention effectiveness.
3Volume of moving object
If circuit components are embedded in a resin substrate to reduce substrate size, then mounting area is reduced and substrate size decreases, but heat generated in reflow process causes solder to re-melt and spread
Solution Approach 1:
The invention applies preliminary anti-action by forming the wetting prevention region on the metal foil before the reflow soldering process. This pre-established low-wettability barrier prevents solder from spreading when heat causes re-melting during subsequent reflow processes, especially in multilayer structures where components are mounted and removed multiple times. The wetting prevention region is prepared in advance to counteract the harmful effect of heat-induced solder流动.
4Productivity
If the distance between lands is decreased to increase density and reduce substrate size, then substrate integration increases, but solder-flow resistance requirement becomes more stringent
Solution Approach 1:
The invention enables high substrate density with stringent solder-flow resistance by applying local quality differentiation. Each land region has high wettability to hold minimal solder/conductive adhesive, while the surrounding wetting prevention region has low wettability to prevent spread. This allows lands to be placed close together to increase density while the wetting prevention regions prevent solder flow between adjacent lands, maintaining reliability even at high densities.
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 approach significantly reduces the risk of short circuits and solder flow, enhances bonding strength, and improves reliability by minimizing the amount of solder or conductive adhesive used, while maintaining the structural integrity of the substrate.
Implementation Method 1
a wetting prevention region surrounding the land regions and having an inferior wettability to solder or conductive adhesive as compared to that of the land regions
Implementation Method 2
a resin sheet made of an inorganic filler and a thermosetting resin is disposed on and pressure bonded to the metal foil
Implementation Method 3
the resin sheet is thermally cured to form a resin layer in which the circuit components are embedded therein
Data Source
AI summary
A method for manufacturing a substrate having built-in components prevents a short circuit caused by the spread of solder or conductive adhesive. Land regions to connect a circuit component and a wetting prevention region surrounding the land regions are formed on one primary surface of a metal foil. Terminal electrodes of the circuit component are electrically connected to the land regions using solder, and an uncured resin is disposed on and pressure bonded to the metal foil and the circuit component, so that a resin layer in which the circuit component is embedded is formed. Subsequently, a wiring pattern is formed by processing the metal foil. The wetting prevention region is a region obtained by roughening or oxidizing one primary surface of the metal foil so as to reduce solder wettability.