3D Stacked Semiconductor Packages Using Pre-Formed Connectors
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Solution Overview
Problem
Existing semiconductor package manufacturing processes, such as those described in U.S. Pat. No. 6,710,454 and JP2004-128523, risk damaging sub-packages during connector formation steps, leading to package failure and increased costs due to complex and error-prone processing steps.
Innovation Solution
A semiconductor package design comprising a first Wafer-Level Chip-Scale Package (WLCSP) with a connection face and a second WLCSP mounted adjacent to its attachment face, using connectors like solder balls or bumps for efficient packaging density and simplified fabrication, with an attachment means like epoxy adhesive to enhance reliability and protect against environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex connector formation steps are used to create connectors on sub-packages, then electrical connection capability is improved, but manufacturing complexity and risk of damage increase
Solution Approach 1:
The patent applies preliminary action by pre-forming connectors on the first sub-package before mounting the second sub-package. The connectors are created during the first sub-package fabrication process, eliminating the need for complex post-assembly connector formation steps. This resolves the contradiction by establishing electrical connection capability in advance while avoiding the manufacturing complexity and damage risk associated with forming connectors after assembly.
2Reliability
If additional processing steps are performed after sub-packages are combined, then electrical connection is established, but risk of damaging sub-packages increases
Solution Approach 1:
The patent performs the preliminary action of forming connectors and establishing electrical connection pathways before the sub-packages are combined. The first sub-package is fabricated with its connectors already in place, and the second sub-package is mounted directly onto it. This eliminates the need for additional processing steps after combination, thereby maintaining package integrity and avoiding damage while still achieving reliable electrical connection.
3Reliability
If traditional packaging methods are used with area overhead, then device protection is improved, but circuit board space utilization decreases
Solution Approach 1:
The patent transitions from traditional two-dimensional planar packaging to three-dimensional vertical stacking. By mounting the second sub-package vertically on top of the first sub-package, the design achieves device protection through layered encapsulation while dramatically reducing the footprint area on the circuit board. This dimensional change resolves the contradiction between protection and space utilization.
Solution Approach 2:
The patent applies the nesting principle by placing the second sub-package within the vertical space above the first sub-package. The encapsulant material flows around both sub-packages, creating a nested protective structure. This allows device protection to be maintained through encapsulation while minimizing the horizontal area occupied, as the protective layers are stacked vertically rather than extending outward.
4Ease of manufacture
If pre-formed connectors are used to simplify fabrication, then manufacturing ease is improved, but height tolerance compensation becomes critical
Solution Approach 1:
The patent applies parameter changes by utilizing the flow characteristics of the encapsulant material to compensate for height tolerances. The encapsulant is applied in a molten or viscous state that allows it to flow and adapt to variations in connector height, then cured to form a rigid protective structure. This change in the physical state parameter of the encapsulant enables easy manufacture with pre-formed connectors while tolerating height variations.
Solution Approach 2:
The patent applies beforehand cushioning by using the encapsulant material to absorb and compensate for height tolerance variations before the final cured structure is formed. The encapsulant is applied in excess and allowed to flow around the connectors, creating a cushioning layer that accommodates height differences. Once cured, this encapsulant provides both mechanical protection and tolerance compensation, enabling the use of pre-formed connectors without strict height control.
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 increases packaging density on circuit boards without modifying the board, reduces processing steps that could damage packages, and minimizes defects, thereby improving yield and cost-effectiveness by using pre-formed connectors and attachment methods that compensate for height tolerances and provide mechanical robustness.
Implementation Method 1
with an attachment means like epoxy adhesive to enhance reliability and protect against environmental factors
Implementation Method 2
using connectors like solder balls or bumps for efficient packaging density and simplified fabrication
Data Source
AI summary
A semiconductor package comprising a first semiconductor sub-package (40) having a connection face (44) with un-supported connectors (21) depending therefrom arranged to electrically connect a first semiconductor device contained therein to an external circuit, and at least one second semiconductor sub-package (42) also having a connection face (46) with un-supported connectors (25) depending therefrom arranged to electrically connect a second semiconductor device contained therein to an external circuit, the second semiconductor sub-package (42) also having an attachment face (48), on an opposite side thereof from the connection face (46); wherein the second semiconductor sub-package (42) is mounted on the first semiconductor sub-package (40) such that its attachment face (48) is coupled to the connection face (44) of the first semiconductor sub-package (40).