Microelectronic Workpiece Projections Reduce Underfill Voids
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Solution Overview
Problem
Conventional flip-chip assembly methods for microelectronic devices often result in vulnerable mechanical connections due to air bubbles and voids in the underfill material, leading to potential damage during high temperature processes and inefficient manufacturing time, as well as incomplete contact between solder balls and conductive bumps.
Innovation Solution
A microelectronic workpiece design featuring a substrate with a projection or ridge and conductive traces, where a protective coating is applied to create a generally planar surface, reducing the need for excessive underfill material and minimizing the formation of voids, thereby enhancing the robustness and reliability of the mechanical and electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flip-chip assembly methods are used with large gaps between die and substrate, then the die can be properly positioned and connected, but air bubbles and voids form in the underfill material leading to vulnerable mechanical connections
Solution Approach 1:
The patent applies preliminary action by pre-forming protrusions on the substrate surface before die attachment. These protrusions extend into the gap between the die and substrate, creating a structural framework that prevents underfill material from trapping air bubbles and voids during the attachment process. The protrusions are prepared in advance to guide the underfill material flow and ensure complete gap filling without void formation.
Solution Approach 2:
The patent uses protrusions as intermediary structures between the die and substrate. These protrusions act as mediators that facilitate the flow of underfill material into the gap while preventing air entrapment. The protrusions transfer and distribute the underfill material evenly, ensuring complete wetting of the die-substrate interface without forming harmful voids.
2Reliability
If conventional underfilling methods are used to fill large gaps, then the die is protected from environmental factors, but the process is time-consuming due to large volumes of fill material requiring extended curing time
Solution Approach 1:
The patent applies segmentation by dividing the large gap between die and substrate into smaller segments using protrusions. The protrusions create multiple smaller void spaces rather than one large continuous gap, allowing underfill material to be distributed and cured in smaller volumes simultaneously. This segmentation reduces the overall curing time while maintaining complete protection against environmental factors.
Solution Approach 2:
The patent uses partial action by having protrusions extend only partially into the gap rather than filling the entire space. This partial extension is sufficient to guide underfill material flow and reduce void formation without requiring excessive amounts of underfill material, thereby reducing curing time while maintaining adequate protection.
3Reliability
If solder balls are made large to extend between bumps and contacts, then electrical connections can be established, but not all solder balls make complete contact leading to open circuits
Solution Approach 1:
The patent replaces the mechanical reliance on large solder balls for electrical connection with a structural support system using protrusions. The protrusions provide mechanical support and positioning that ensures proper alignment and contact between solder balls and conductive bumps, eliminating the need to rely on oversized solder balls. This substitution improves manufacturing precision while maintaining electrical connection reliability.
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 design significantly reduces the likelihood of voids and improves the robustness of connections between the microelectronic die and the substrate, enhancing the reliability and efficiency of the manufacturing process by eliminating large cavities and ensuring complete contact between conductive elements.
Implementation Method 1
the underfill material is drawn into the gap by capillary effects
Data Source
AI summary
Microelectronic workpieces and methods for manufacturing microelectronic devices using such workpieces are disclosed. In one embodiment, a microelectronic assembly comprises a support member having a first side and a projection extending away from the first side. The assembly also includes a plurality of conductive traces at the first side of the support member. Some of the conductive traces include bond sites carried by the projection and having an outer surface at a first distance from the first side of the support member. The assembly further includes a protective coating deposited over the first side of the support member and at least a portion of the conductive traces. The protective coating is generally co-planar with the outer surface of the bond sites carried by the projection.