Flush Post Structure for WLCSP Miniaturization and IR Shielding
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Solution Overview
Problem
The existing Wafer Level Chip Size Package (WLCSP) technology faces limitations in downsizing semiconductor devices due to the need for a clearance between solder balls, which restricts the reduction of package size and allows for overhangs without bumps or solder balls, thereby limiting miniaturization and introducing potential issues with infrared ray penetration affecting IC functionality.
Innovation Solution
A semiconductor device with a post structure where the side surface of the post is flush with the sealing resin layer, eliminating overhangs and allowing for reduced package size, and an integrated shielding film to prevent infrared ray penetration, using materials like metallic or resin layers with shielding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clearance is provided between solder balls to prevent contact during mounting, then reliability is improved, but package size cannot be reduced below a constant level
Solution Approach 1:
The patent extracts the harmful function of the overhang (which provided no functional value and increased package size) by repositioning the post to be flush with the sealing resin layer. This eliminates the need for clearance between solder balls while maintaining reliability, as the post structure itself provides adequate spacing without requiring additional overhang space.
Solution Approach 2:
Instead of extending the post beyond the sealing resin layer to create overhang (conventional approach), the patent inverts the design by making the post flush with the sealing resin layer. This inversion eliminates the overhang and reduces package size while still providing the necessary structural support and spacing for solder balls.
2Area of stationary object
If bumps are arranged inward beyond the electrodes to avoid increasing package size, then package size is reduced, but overhangs are created where neither bumps nor solder balls are arranged
Solution Approach 1:
The patent removes the overhang structure entirely by positioning the post flush with the sealing resin layer. This eliminates the non-functional overhang regions while maintaining compact package dimensions, as the post itself provides the necessary structural framework without requiring additional extending space.
Solution Approach 2:
Rather than extending posts beyond the sealing resin to create overhangs (conventional design), the patent inverts the approach by making posts flush with the sealing resin layer. This inversion eliminates overhangs and their associated complexities while achieving compact packaging through efficient use of space.
3Area of stationary object
If side surface of post is exposed from sealing resin layer (flush alignment), then package size is reduced, but post structure becomes more complex
Solution Approach 1:
The post structure serves multiple functions: it provides structural support, enables flush alignment with the sealing resin layer to eliminate overhangs, and facilitates solder ball attachment. By making the post flush with the sealing resin, a single structural element achieves multiple objectives without requiring additional components, thereby reducing overall package size while maintaining manageable complexity.
Solution Approach 2:
The patent merges the post structure with the sealing resin layer boundary, making them aligned at the same level. This integration eliminates the need for separate overhang structures and combines the functional requirements into a unified design, reducing package size while avoiding the complexity of multi-level structures.
4Ease of manufacture
If conventional WLCSP structure is used with overhangs, then manufacturing is easier, but infrared rays can penetrate affecting IC functionality
Solution Approach 1:
The patent converts the previously non-functional overhang region into a beneficial shielding structure by positioning the post flush with the sealing resin layer and extending the shielding film to cover the post's side surface. This transforms the space that previously offered no protection into an active barrier against infrared radiation, protecting the IC while maintaining manufacturing feasibility through integrated film application.
Solution Approach 2:
The shielding film serves dual functions: it provides electrical connection through the post structure and simultaneously blocks infrared ray penetration. By making the post flush with the sealing resin and extending the shielding film to cover the post's side surface, a single structure achieves both electrical functionality and infrared protection, eliminating the need for separate shielding components and simplifying manufacturing.
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 solution enables a smaller package size and prevents infrared ray interference, enhancing the semiconductor device's performance and reliability by eliminating overhangs and shielding unwanted radiation.
Implementation Method 1
a shielding film made of a material having shielding properties against infrared rays and covering the side surface of the semiconductor chip
Data Source
AI summary
A semiconductor device according to the present invention includes a semiconductor chip having a front surface and a rear surface, a sealing resin layer stacked on the front surface of the semiconductor chip, a post passing through the sealing resin layer in the thickness direction and having a side surface flush with a side surface of the sealing resin layer and a forward end surface flush with a front surface of the sealing resin layer, and an external connecting terminal provided on the forward end surface of the post.