Wire Bond Microcontacts for High Aspect Ratio Package-on-Package Assembly
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Solution Overview
Problem
Conventional etching processes are limited in forming microcontacts with high aspect ratios and arrays of microcontacts with small pitch or spacing, making it difficult to create efficient connections between microelectronic packages in stacked arrangements.
Innovation Solution
A method involving the formation of wire bonds on a substrate, where a metal wire is bonded to conductive elements, cut to define end surfaces, and encapsulated with a dielectric layer, allowing for vertical connections and efficient package-on-package electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used to form microcontacts, then the manufacturing process is simple, but the aspect ratio and pitch of microcontacts are limited
Solution Approach 1:
The patent replaces conventional chemical etching processes with a mechanical wire bonding process to form microcontacts. Wire bonds are mechanically attached to conductive elements and extend through the encapsulation layer, eliminating the limitations of etching processes while enabling high aspect ratios and small pitches. This mechanical approach allows precise control over microcontact geometry without complex etching masks or multiple processing steps.
Solution Approach 2:
The patent transitions from planar microcontacts formed by etching to vertical wire bonds that extend through the encapsulation layer. This dimensional change allows microcontacts to achieve high aspect ratios by utilizing the vertical dimension rather than being constrained to the planar surface, thereby solving the aspect ratio limitation of conventional etching processes.
2Reliability
If wire bonds are used for package-on-package connections, then connectivity and mechanical strength are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the wire bonding process with the encapsulation process by forming wire bonds that extend through the encapsulation layer rather than requiring separate bonding and encapsulation steps. This integration simplifies the overall manufacturing process while maintaining the reliability benefits of wire bonds, as the encapsulation material simultaneously provides structural support and electrical insulation for the wire bonds.
Solution Approach 2:
The wire bonds serve multiple functions: they provide electrical connection between packages, mechanical strength for the connection, and structural support within the encapsulation layer. This multi-functionality reduces the need for additional components or processes, thereby simplifying the overall manufacturing complexity while improving connection reliability.
3Speed
If stacked package arrangements are used, then interconnection distance is reduced for high-speed operation, but manufacturing precision requirements increase
Solution Approach 1:
The wire bonds automatically align with conductive elements through the bonding process, which inherently positions the wire bond base at the conductive element location. This self-alignment mechanism eliminates the need for high-precision external alignment processes, thereby reducing manufacturing precision requirements while enabling the short interconnection distances needed for high-speed signal propagation in stacked packages.
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 enables the creation of microelectronic packages with improved connectivity and reduced size, facilitating high-speed operations by allowing for shorter interconnections and robust mechanical and electrical connections between packages.
Implementation Method 1
heating and pressing the portion of the wire to a conductive element to bond the portion of the wire to the conductive element
Implementation Method 2
heating and pressing the portion of the wire to a conductive element to bond the portion of the wire to the conductive element
Implementation Method 3
clamping a portion of the wire within the bonding tool
Implementation Method 4
heating and pressing the portion of the wire to a conductive element
Implementation Method 5
cutting the metal wire at a location between the clamped portion and the base portion to at least partially define an end surface of the wire bond
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
A microelectronic assembly (10) includes a substrate (12) having a first and second opposed surfaces. A microelectronic element (22) overlies the first surface and first electrically conductive elements (28) can be exposed at at least one of the first surface or second surfaces. Some of the first conductive elements (28) are electrically connected to the microelectronic element (22). Wire bonds (32) have bases (34) joined to the conductive elements (28) and end surfaces (38) remote from the substrate and the bases, each wire bond defining an edge surface (37) extending between the base and the end surface. An encapsulation layer (42) can extend from the first surface and fill spaces between the wire bonds, such that the wire bonds can be separated by the encapsulation layer. Unencapsulated portions of the wire bonds (32) are defined by at least portions of the end surfaces (38) of the wire bonds that are uncovered by the encapsulation layer (42).