Exposed Surface Stacked Semiconductor Package Design
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Solution Overview
Problem
Current stacked package assemblies face challenges in design flexibility, cost, and manufacturability due to the need for matching pad arrangements on top and bottom substrates, which limits the ability to mix-and-match components from different suppliers and requires redesign when changing chip or package types, and restricts the addition or removal of functionalities without requalifying the entire assembly.
Innovation Solution
A semiconductor package design where a first package substrate has a die mounted and electrically connected, with a second substrate mounted over it, allowing for z-interconnection via wire bonds and exposing both substrates for second-level interconnections, enabling the use of various components and flexibility in stacking additional packages or die without reconfiguring the entire assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If matching pad arrangements are required on top and bottom substrates for stacked packages, then manufacturing precision and reliability are improved, but design flexibility and adaptability deteriorate
Solution Approach 1:
The invention divides the interconnection system into two independent segments: the first substrate with its pad arrangement and the second substrate with its pad arrangement. By separating these previously matched requirements into independent segments, each substrate can be designed and sourced independently, eliminating the need for matching pad arrangements while maintaining reliable electrical connections through the wire bond interconnect layer.
Solution Approach 2:
The wire bond interconnect layer serves as an intermediary between the first substrate and second substrate. This intermediary component absorbs the mismatch between different pad arrangements, allowing the first and second substrates to have different pad configurations while still achieving reliable electrical interconnection. The wire bonds act as a flexible mediator that adapts to different pad layouts on either side.
2Ease of manufacture
If components are stacked with matching pad arrangements, then manufacturing complexity is reduced, but productivity and time-to-market deteriorate
Solution Approach 1:
The manufacturing process is segmented into independent steps for each substrate. The first substrate can be manufactured, tested, and prepared independently from the second substrate. This segmentation allows parallel processing and eliminates the need for coordinated redesign when changing components, significantly reducing time-to-market while the modular wire bond interconnection maintains manufacturing simplicity.
Solution Approach 2:
The first substrate can be fully manufactured, tested, and prepared in advance before the second substrate is added. This preliminary action allows the base package to be completed and qualified independently, enabling faster iteration and integration of additional components without requiring requalification of the entire assembly, thus accelerating time-to-market.
3Reliability
If the entire assembly is reconfigured when changing chip or package types, then reliability is maintained, but loss of time and productivity deteriorate
Solution Approach 1:
The assembly is segmented into independent modules where the first substrate and second substrate can be changed independently. When changing chip or package types, only the affected segment needs to be modified while the other segment remains unchanged, eliminating the need for complete reconfiguration and requalification of the entire assembly, thus reducing redesign time while maintaining reliability through targeted updates.
Solution Approach 2:
The first substrate can be fully designed, manufactured, and tested in advance as a validated base. When changing to different chip or package types, the preliminary-validated first substrate serves as a stable foundation, requiring only minimal updates to the second substrate or interconnect layer, significantly reducing redesign time while preserving the reliability already established in the base assembly.
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 provides excellent manufacturability, high design flexibility, and low cost, allowing for a compact, high-functionality stacked package module with a small footprint, enabling the selection of components from standard packages and facilitating the integration of various functionalities without extensive redesign.
Implementation Method 1
z-interconnection of the first package substrate and the second substrate is by wire bonds connecting the first package substrate and the second substrate
Data Source
AI summary
A semiconductor package subassembly includes a die affixed to, and electrically interconnected with, a die attach side of a first package substrate, and a second substrate having a first side and a second (“land”) side, mounted over the first package with the first side of the second substrate facing the die attach side of the first package substrate, and supported by a spacer or a spacer assembly. Z-interconnection of the package and the substrate is by wire bonds connecting the first and second substrates. The assembly is encapsulated in such a way that both the land side of the second substrate (one side of the assembly) and a portion of the land side of the first package substrate (on the opposite side of the assembly) are exposed, so that second level interconnection and interconnection with additional components may be made.