Circuitized Substrate Bonding via Segmented Solder Paste
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Solution Overview
Problem
Current methods for forming multilayered circuitized substrates face challenges in achieving efficient interconnections between subassemblies, particularly in reducing signal line widths and thru-hole diameters to enhance circuit densification while maintaining reliable electrical connections.
Innovation Solution
A method involving the alignment of conductor pads on two circuitized substrate subassemblies with a flowable dielectric layer and metallic solder paste, bonded together using heat and pressure to form electrical connections, ensuring the dielectric material fills openings without disrupting the bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional lamination procedures are used to bond subassemblies, then assembly is simplified, but signal line widths and thru-hole diameters cannot be reduced sufficiently for high-density circuitry
Solution Approach 1:
The bonding process is segmented into distinct phases: first applying solder paste to conductor pads, then applying dielectric material, and finally applying additional solder paste to fill voids. This segmentation allows each material to be optimized for its specific function without interfering with others, enabling reduced signal line widths and thru-hole diameters while maintaining reliable connections.
Solution Approach 2:
Solder paste is applied to conductor pads before the lamination process begins, and additional solder paste is applied after dielectric material is in place but before final compression. These preliminary actions ensure that bonding surfaces are prepared in advance, allowing for precise control of interconnection quality even with reduced dimensional tolerances.
2Reliability
If solder paste is applied between mating pads to enhance connection, then electrical connection reliability improves, but the bonding process becomes more complex
Solution Approach 1:
The bonding process merges multiple functions into a single lamination step: dielectric material application, void filling, and electrical connection formation all occur simultaneously during one compression and curing cycle. This integration reduces process complexity despite the multi-material nature of the bonding interface.
Solution Approach 2:
Dielectric material serves as an intermediary between conductor pads, providing both electrical insulation and mechanical support, while solder paste acts as an intermediary for forming reliable electrical connections. This use of intermediary materials simplifies the overall bonding process by separating insulation and conduction functions.
3Reliability
If dielectric material is used to insulate external conductive elements, then electrical isolation is achieved, but the bonding interface becomes more complex
Solution Approach 1:
The dielectric material performs multiple functions simultaneously: it provides electrical insulation between conductive elements, fills voids in the bonding interface, and serves as a bonding medium between subassemblies. This multi-functionality reduces bonding interface complexity by consolidating multiple requirements into a single material layer.
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 approach enables sound electrical connections between subassemblies, facilitating high-density circuitry with reduced signal line widths and thru-hole diameters, suitable for complex electronic structures like chip carriers and printed circuit boards.
Implementation Method 1
bonding the first and second circuitized substrate subassemblies together using heat and pressure in such a manner that the metallurgies of the solder paste and metallic conductor pads are combined to form an electrical connection
Implementation Method 2
the metallurgies of the solder paste and metallic conductor pads are combined to form an electrical connection there-between
Data Source
AI summary
A method of making a circuitized substrate assembly in which two or more subassemblies are aligned and bonded together. The bonding, preferably using lamination, results in effective electrical connections being formed between respective pairs of conductors of the subassemblies in such a manner that the metallurgies of the conductors, and those of an interim metallic solder paste, are effectively mixed and the flowable interim dielectric used between the mating subassemblies is forced to flow to engage and surround the conductor coupling, without adversely affecting the electrical connection formed.