Wave Soldering Encapsulation of PCB Terminals to Prevent Tin Whiskers
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Solution Overview
Problem
Tin or tin alloy deposits on exposed electrical terminals of surface mount components tend to form whiskers, reducing the reliability and increasing maintenance costs of electronic components, as existing reflow soldering processes do not effectively encapsulate these terminals.
Innovation Solution
A method involving wave soldering with lead-free solder to encapsulate the electrical terminals of surface mount components on printed circuit boards, eliminating the need for reflow soldering and reducing tin whisker formation by using a lead-free solder to cover the terminals on both surfaces of the board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reflow soldering process is used to solder surface mount components, then the components are attached to the board, but the exposed terminals still form tin whiskers reducing reliability
Solution Approach 1:
The patent applies conformal coating material to the exposed terminals after reflow soldering, converting the harmful exposed tin surfaces into protected surfaces. The coating material encapsulates the terminals, preventing tin whisker formation while maintaining the electrical connections established by reflow soldering.
Solution Approach 2:
The conformal coating creates an inert protective environment around the exposed terminals, isolating them from atmospheric conditions that promote oxidation and whisker growth. This protective barrier effectively creates a controlled environment that prevents the harmful chemical reactions leading to tin whiskers.
2Ease of manufacture
If terminals are left exposed after soldering, then the components are electrically connected, but maintenance costs increase due to tin whisker formation
Solution Approach 1:
The patent applies conformal coating material immediately after the reflow soldering process while the PCB is still in the manufacturing line. This preliminary protective action is taken before the product leaves the factory, preventing tin whisker formation during storage and operation, thereby reducing future maintenance costs without adding complex repair procedures.
3Reliability
If conformal coating is applied to encapsulate terminals, then tin whisker formation is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The conformal coating process serves multiple functions simultaneously: it provides electrical insulation, protects against environmental contaminants, prevents tin whisker formation, and enhances solder joint protection. This multi-functionality justifies the additional manufacturing step by delivering multiple benefits from a single process addition.
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 method effectively reduces tin whisker formation, enhancing the operational reliability of electronic components and minimizing maintenance costs by encapsulating terminals with lead-free solder through wave soldering.
Implementation Method 1
wave soldering the surface mount component on the first surface to the board to encapsulate at least a portion of the electrical terminals of the surface mount component with a lead-free solder
Implementation Method 2
applying an adhesive on the first surface of the board, and adhering the surface mounting component to the first surface
Data Source
AI summary
A method for manufacturing a printed circuit board includes providing a board including a plurality of electrical traces, a first surface, and a second surface opposite the first surface. The method further includes providing at least one surface mount component having a plurality of electrical terminals. The method also includes applying an adhesive on the first surface of the board, and adhering the surface mounting component to the first surface. The method also includes wave soldering the surface mount component on the first surface to the board to encapsulate at least a portion of the electrical terminals of the surface mount component with a lead-free solder.