Copper Pad Structure With Protective Layers for Stable SMT Soldering
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Solution Overview
Problem
Existing surface mounted technology (SMT) in the electronic assembly industry faces issues such as pad corrosion, unfixed soldering, and inability to rework pads due to erosion, leading to unstable soldering strength and reliability.
Innovation Solution
The array substrate includes a base substrate with a first conductive layer having pads made of almost pure Cu with a thickness greater than 2 μm, and electronic elements with pins connected to the pads. Additionally, first protective layers made of conductive materials, such as CuNi, are used between the pins and pads to prevent erosion and ensure stable soldering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional SMT pads are used with conventional materials and thickness, then manufacturing cost is controlled, but pad erosion and corrosion occur during soldering leading to unstable soldering strength
Solution Approach 1:
The pad structure uses a composite material system consisting of a Cu layer (≥2μm thick, ≥99% purity) combined with protective layers containing molybdenum-niobium alloy or molybdenum-nickel-titanium alloy. This composite structure provides both excellent electrical conductivity and resistance to soldering flux erosion, resolving the contradiction between maintaining soldering strength and preventing pad corrosion.
Solution Approach 2:
The patent applies preliminary protective measures by pre-coating the Cu pad surface with protective layers before the soldering process. These protective layers act as a barrier against soldering flux, preventing erosion and corrosion before they can damage the underlying Cu structure, thereby ensuring stable soldering strength throughout the assembly process.
2Reliability
If Cu content in the first metal layer is increased to improve conductivity, then electrical performance improves, but susceptibility to oxidation and erosion increases
Solution Approach 1:
The patent creates a composite pad structure where a high-purity Cu layer (≥99% Cu content, thickness ≥2μm) provides excellent electrical conductivity, while overlying protective layers containing molybdenum-niobium alloy or molybdenum-nickel-titanium alloy provide oxidation and erosion resistance. This composite approach allows the Cu layer to maintain high conductivity without being directly exposed to harmful environments.
Solution Approach 2:
The protective layers serve as intermediary barriers between the high-purity Cu layer and the corrosive soldering flux environment. These intermediate layers prevent direct contact between the Cu and oxidizing agents, allowing the Cu to maintain its superior electrical properties without suffering from oxidation or erosion.
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 enhances soldering stability and strength by preventing pad erosion and corrosion, allowing for reliable connections between the electronic elements and the substrate, even under fluctuating soldering conditions.
Implementation Method 1
a first conductive layer, disposed on the base substrate, where the first conductive layer includes a plurality of pads
Implementation Method 2
the plurality of pins are connected with the plurality of pads
Data Source
AI summary
Provided are an array substrate and an electronic apparatus. The array substrate includes: a base substrate; a first conductive layer on the base substrate, where the first conductive layer includes a plurality of pads, each pad includes a first metal layer, a material of the first metal layer includes Cu, a content of the Cu is greater than or equal to 99%, and a thickness of the first metal layer is greater than 2 μm; and an electronic element disposed on a side of the first conductive layer facing away from the base substrate, where the electronic element includes an electronic element body and a plurality of pins disposed on a side of the electronic element body facing the base substrate, and the pins are connected with the pads.