Adhesive-Bonded Multi-Chip Module Substrates
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Solution Overview
Problem
Multi-chip modules (MCMs) face a tradeoff between adhesive strength and signal quality due to the thickness of the adhesive layer, where thick adhesives compromise signal coupling and thin adhesives are prone to shearing failure under stress.
Innovation Solution
A multi-chip module design featuring substrates with recessed channels or mesas that allow for an adhesive layer thicker than the spacing between proximity connectors, providing mechanical coupling and shear strength while maintaining zero or near-zero spacing for high signal quality, using adhesives like epoxy glue that can be air, thermally, pressure, or optically cured.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick adhesive layer is used, then the adhesive provides sufficient shear strength and reliability, but the spacing between proximity connectors increases, which decreases signal coupling and signal quality
Solution Approach 1:
The patent introduces channels that extend in the vertical dimension (below the substrate surface) to increase the adhesive bonding area and thickness without increasing the horizontal spacing between proximity connectors. This allows the adhesive layer to be thicker than the connector spacing, providing sufficient shear strength while maintaining tight connector spacing for optimal signal coupling.
Solution Approach 2:
The channels are recessed into the substrate, creating a nested structure where the adhesive is contained within the channel volume. This nested configuration allows the adhesive to occupy three-dimensional space efficiently, maximizing bond strength while minimizing the overall profile height and maintaining connector alignment.
2Manufacturing precision
If a thin adhesive layer is used, then the signal coupling and signal quality are improved, but the adhesive layer is susceptible to shearing failure under lateral stress and strain
Solution Approach 1:
By extending channels vertically below the substrate surface, the patent increases the adhesive layer thickness in the vertical dimension without compromising the horizontal alignment and spacing of proximity connectors. This provides sufficient adhesive volume for shear strength while maintaining thin overall profile for signal integrity.
Solution Approach 2:
The patent uses epoxy glue as the adhesive material within the channel structure, creating a composite system where the adhesive fills the channel volume and bonds to the substrate walls, providing enhanced mechanical strength through the combination of substrate and adhesive materials.
3Strength
If the adhesive layer thickness is increased to provide sufficient bond strength, then reliability improves, but the spacing between proximity connectors must increase, compromising signal quality
Solution Approach 1:
The channel structure enables the adhesive thickness to be increased in the vertical dimension while keeping the horizontal connector spacing minimal. The channels extend below the substrate surface, allowing the adhesive to achieve greater thickness for improved bond strength without increasing the horizontal distance between proximity connectors.
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 design enhances the reliability and signal integrity of MCMs by decoupling adhesive thickness from spacing, offering improved shear strength and compatibility with high-volume manufacturing processes.
Implementation Method 1
an adhesive, which is mechanically coupled to the first substrate and the inner surface, and which has a thickness that is larger than the spacing, maintains alignment and provides shear strength in the MCM
Implementation Method 2
an adhesive, which is mechanically coupled to the first substrate and the inner surface, and which has a thickness that is larger than the spacing, maintains alignment and provides shear strength in the MCM
Data Source
AI summary
A multi-chip module (MCM) is described in which at least two substrates are mechanically coupled by an adhesive layer that maintains alignment and a zero (or near zero) spacing between proximity connectors on surfaces of the substrates, thereby facilitating high signal quality during proximity communication between the substrates. In order to provide sufficient shear strength, the adhesive layer has a thickness that is larger than the spacing. This may be accomplished using one or more positive and/or negative features on the substrates. For example, the adhesive may be bonded to: one of the surfaces and an inner surface of a channel that is recessed below the other surface; inner surfaces of channels that are recessed below both of the surfaces; or both of the surfaces. In this last case, the zero (or near zero) spacing may be achieved by disposing proximity connectors on a mesa that protrudes above at least one of the substrate surfaces.