U-Shaped Conductive Contacts for Solderless POP Stacking
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Solution Overview
Problem
The reliability of electronic components in Package On Package (POP) devices is compromised due to thermal damage from repeated solder reflow processes, making it difficult to connect and separate wiring substrates without damaging the components and limiting the number of reflow times.
Innovation Solution
The use of U-shaped conductive contacts on the peripheral edges of wiring substrates, which are connected without solder, allowing for elastic dispersion of pressure and secure stacking without the need for solder reflow, thereby preventing thermal damage and enabling easy separation and replacement of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder balls are reflowed to connect upper and lower wiring substrates, then the wiring substrates are electrically and mechanically connected, but the electronic components mounted on each wiring substrate are reflowed multiple times and are thus thermally damaged, so that reliability of the electronic components may be lowered
Solution Approach 1:
The patent extracts the harmful reflow process from the connection method. Instead of using solder balls that require reflow heating, the invention uses conductive contacts with elastic deformation to achieve mechanical and electrical connection without thermal processing, thereby protecting electronic components from thermal damage while maintaining connection reliability
Solution Approach 2:
The patent replaces the thermal-mechanical solder reflow system with a pure mechanical connection system. Conductive contacts with U-shaped cross sections deform elastically under compression to create reliable electrical connections between substrates without requiring heat, thus substituting thermal energy with mechanical energy for the connection process
2Strength
If conductive contacts are formed with U-shape, then the conductive contacts have elasticity and it is possible to disperse pressure when stacking wiring substrates, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies curvature to the conductive contacts by forming them with U-shaped cross sections instead of straight cylindrical shapes. This curvature provides elastic deformation capability under compression, allowing the contacts to disperse pressure evenly across the contact area while maintaining electrical conductivity, thus improving mechanical strength without significantly complicating manufacturing
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 solution prevents thermal damage to electronic components, maintains reliability, allows for easy separation and replacement of wiring substrates, and reduces manufacturing complexity by eliminating the need for solder reflow, while maintaining high functionality and compact size.
Implementation Method 1
the first to third conductive contacts are respectively formed to have a U-shape, so that the conductive contacts have elasticity and it is possible to disperse a pressure, which is to be applied when stacking the first wiring substrate and the second wiring substrate
Data Source
AI summary
An electronic device includes a first wiring substrate having a first main surface, first conductive contacts, each of which is provided upright on the first main surface, has a U-shape opening toward a side of the first wiring substrate, and comprises a first contact part extending toward the side of the first wiring substrate, a second wiring substrate having a second main surface, second conductive contacts, each of which is provided upright on the second main surface, has a U-shape opening toward a side of the second wiring substrate, and comprises a second contact part extending toward the side of the second wiring substrate and being in contact with the first contact part, and, third conductive contacts, each of which has a U-shape opening toward the conductive contacts and is configured to sandwich the first and second contact parts and to fix the first and second wiring substrates.