Inverted Solder Paste Transfer for Non-Planar PCBs
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Solution Overview
Problem
Conventional solder paste transfer processes are inefficient and prone to defects when applied to non-planar surface mount assemblies, as they cannot accurately position solder paste on non-flat circuit cards, leading to increased labor costs and potential electrical failures.
Innovation Solution
A solder paste transfer process involving a fixture with non-wettable transfer tools that are inverted over the circuit board, using a laser-cut stencil to apply controlled amounts of solder paste, ensuring precise placement and preventing bridging between solder joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional automated screen print process is used, then flat circuit cards can be efficiently processed, but non-planar surfaces cannot be accurately positioned
Solution Approach 1:
The transfer tools are inverted and disposed proximate to the non-planar surface from below, allowing the solder paste to be transferred upward onto the solder pad locations. This inversion enables the process to accommodate non-planar surfaces while maintaining automated efficiency and positioning accuracy.
Solution Approach 2:
Transfer tools with non-wettable surfaces act as intermediaries between the solder paste and the circuit card. The solder paste is first applied to the transfer tools, then transferred to the solder pad locations on the non-planar surface, enabling precise placement without direct contact between the dispensing system and the complex surface geometry.
2Manufacturing precision
If manual dispensing process is used for non-planar surfaces, then positioning flexibility is achieved, but labor costs increase and defects occur
Solution Approach 1:
The non-wettable surface of the transfer tool automatically retains the solder paste through surface tension, and the reflow process causes the solder paste to naturally transfer to the solder pad locations below. This self-service mechanism eliminates the need for complex dispensing systems while maintaining precision.
3Measurement precision
If auger valves are used for dispensing, then dispense precision improves, but operational complexity and variable control increase
Solution Approach 1:
The complex auger valve mechanism is extracted from the process and replaced with simple transfer tools that hold solder paste through surface tension. The precision previously achieved by complex mechanical valves is now achieved through the physical chemistry of the non-wettable surface interface.
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 method allows for accurate and efficient application of solder paste to non-planar surfaces, reducing labor costs and ensuring quality by preventing electrical failures through precise solder joint formation.
Implementation Method 1
each of the respective surfaces is non-wettable with respect to the solder paste
Implementation Method 2
reflowing the solder paste to flow from the multiple transfer tools to the solder pad locations
Data Source
AI summary
A solder paste transfer process is provided and includes defining multiple arrangements of solder pad locations on a surface, applying solder paste onto multiple transfer tools coupled to a fixture in a pre-defined configuration reflective of the multiple arrangements, disposing the fixture such that the multiple transfer tools are disposed in an inverted orientation proximate to the surface and reflowing the solder paste to flow from the multiple transfer tools to the solder pad locations.