Semiconductor Package Assembly Using Passive Standoffs Against Solder Bridging
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Solution Overview
Problem
The semiconductor industry faces challenges with solder bridging between semiconductor packages and printed circuit boards, particularly due to warpage and the need for additional process steps when using standoffs or special solder balls, which can increase manufacturing complexity and risk of electrical shorts.
Innovation Solution
The use of passive devices, including capacitors, resistors, or inductors, as standoffs on the substrate, which are electrically isolated from the semiconductor chip and attached in the same fabrication process as operable passive devices, to maintain a minimum distance between the package and the board, preventing solder bridging during the solder reflow process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional standoffs or special solder balls are used to prevent solder bridging, then solder bridging is prevented, but additional process steps are required which increase manufacturing complexity
Solution Approach 1:
The patent combines the standoff function with the passive device (capacitor, resistor, or inductor) into a single integrated component. The passive device is mounted on the substrate and serves dual purposes: providing its electrical function and acting as a standoff to prevent solder bridging. This eliminates the need for separate standoff components and additional mounting process steps, thereby reducing manufacturing complexity while maintaining solder bridging prevention.
Solution Approach 2:
The passive device is designed to perform multiple functions simultaneously: it provides its primary electrical function (capacitance, resistance, or inductance) and also serves as a mechanical standoff structure. By making the passive device multi-functional, the patent eliminates the need for dedicated standoff components, simplifying the manufacturing process while ensuring reliable solder joint formation.
2Reliability
If standoffs are used to maintain distance between package and board, then solder bridging is prevented, but the manufacturing process requires extra steps
Solution Approach 1:
The standoff function is merged with the passive device mounting process. The passive device is attached to the substrate in the same fabrication step where other passive devices are mounted, eliminating the need for a separate standoff installation process. This integration maintains the necessary distance between the package and board for reliable solder joints while simplifying manufacturing.
3Device complexity
If passive devices are used as standoffs, then manufacturing complexity is reduced by eliminating extra process steps, but the passive devices must be electrically isolated to avoid interfering with chip performance
Solution Approach 1:
The passive devices used as standoffs are selectively electrically isolated from the semiconductor chip by positioning them on specific regions of the substrate that are electrically isolated from the chip's signal paths. This local electrical isolation ensures that the passive devices can serve as standoffs without interfering with the chip's electrical performance, while still providing the necessary mechanical support and solder bridging prevention.
Data Source
AI summary
A semiconductor package assembly includes a semiconductor package that includes a semiconductor chip bonded to a substrate. The assembly also includes a plurality of passive devices mounted on a bottom surface of the substrate opposite the semiconductor chip, the plurality of passive devices including a plurality of operable passive devices and a plurality of standoff passive devices, wherein a height of each of the plurality of standoff passive devices is greater than a height of any of the plurality of operable passive devices. The assembly also includes a plurality of solder structures attached to the bottom surface of the substrate. When mounted on a circuit board, the standoff passive devices prevent solder bridging.