Circuit Board Surface Treatment Prevents Solder Overflow
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Solution Overview
Problem
Conventional circuit board surface treatment processes lead to solder overflow and short circuits due to the protruding oxidation protection layer during the reflow bonding process, as the layer thickness is not adequately controlled, causing the melted solder to extrude and connect adjacent pads.
Innovation Solution
A surface treatment process involving the formation of a thinner first oxidation protection layer on the circuit board, with a cover layer and subsequent black oxidation process, ensuring the oxidation protection layer's thickness is equal to or less than the black oxide layer's thickness, preventing solder overflow by reducing the extrusion risk during reflow bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick oxidation protection layer is formed on the pads by electroplating, then the solder protection effect is improved, but the solder may be extruded by the protruding oxidation protection layer during reflow, causing overflow to adjacent pads and short circuits
Solution Approach 1:
The patent changes the thickness parameter of the oxidation protection layer from the conventional thick layer (5-7 μm) to a thin layer (1-3 μm) that is thinner than or equal to the black oxide layer thickness. This parameter change eliminates the protrusion problem while maintaining adequate solder protection, preventing solder extrusion and overflow to adjacent pads during reflow bonding.
Solution Approach 2:
The patent applies different oxidation protection layer thicknesses to different functional areas: the first oxidation protection layer on pads is kept thin (1-3 μm) to prevent solder extrusion, while the second oxidation protection layer on other circuit layer portions can be thicker for adequate protection. This localized quality differentiation optimizes both solder joint reliability and protection effectiveness.
2Reliability
If the oxidation protection layer thickness is increased to ensure solder protection, then the protection effect is improved, but the manufacturing precision is reduced due to difficulty in controlling the thickness relationship between oxidation protection layer and black oxide layer
Solution Approach 1:
The patent establishes a precise thickness parameter relationship where the first oxidation protection layer thickness (1-3 μm) is controlled to be thinner than or equal to the black oxide layer thickness. This parameter specification enables consistent manufacturing by providing clear thickness targets, improving manufacturing precision while ensuring adequate solder protection.
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 process effectively prevents solder overflow and short circuits by maintaining a controlled oxidation protection layer thickness, ensuring reliable electrical connections between the circuit board and chip without adjacent pad interference.
Implementation Method 1
a first oxidation protection layer is plated on the first circuit layer in the third opening and a second oxidation protection layer is plated on the second circuit layer in the second opening by immersion
Implementation Method 2
a black oxidation process is performed on the first circuit layer exposed by the first oxidation protection layer, so as to form a black oxide layer
Data Source
AI summary
A surface treatment process for a circuit board is provided. The circuit board includes a substrate, a first circuit layer disposed on an upper surface of the substrate, and a second circuit layer disposed on a lower surface of the substrate. The first circuit layer is electrically connected to the second circuit layer. In the surface treatment process for the circuit board, a first oxidation protection layer and a second oxidation protection layer are respectively formed on a portion of the first circuit layer and a portion of the second circuit layer by immersion. Afterwards, the first circuit layer exposed by the first oxidation protection layer is subjected to black oxidation to form a black oxide layer. The thickness of the first oxidation protection layer is thinner than or equal to the thickness of the black oxide layer.