Semiconductor Package Lid Spacers to Prevent BGA Bridging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The increasing size and weight of multi-chip packages cause deformation during surface mount technology processes due to mismatched coefficients of thermal expansion, leading to potential electrical short-circuits from solder bump bridging.
Innovation Solution
Incorporation of a spacer structure within the package lid that extends through the package substrate, maintaining a uniform gap between the substrate and the printed circuit board, preventing deformation and bridging of solder balls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-chip packages are assembled to increase computation speed and heterogeneous integration, then the quantity of chips and functionality are improved, but package size and weight increase causing BGA deformation and solder bump bridging
Solution Approach 1:
The package structure is segmented into multiple functional layers including substrate, chip, mold compound, and package lid, with each layer serving specific purposes. This segmentation allows optimization of each component's properties to balance integration capability with weight management.
Solution Approach 2:
The package utilizes composite materials including epoxy mold compound with silica filler, copper lead frame, and solder bump alloys. These composite materials provide optimized combinations of strength, weight, and thermal properties to support heterogeneous integration while minimizing excessive weight gain.
2Adaptability or versatility
If multi-chip packages are assembled to increase computation speed and heterogeneous integration, then the quantity of chips and functionality are improved, but package size increases causing BGA deformation and solder bump bridging
Solution Approach 1:
The package is divided into distinct functional segments (substrate, chip, mold compound, lid) that can be independently optimized. This allows the overall package size to be controlled while maintaining the ability to integrate multiple chips for enhanced functionality.
Solution Approach 2:
The mold compound acts as a flexible encapsulating layer that conforms to the chip and substrate geometry, providing mechanical support and protection while allowing compact packaging design that minimizes overall package footprint.
3Productivity
If package size and weight increase, then more chips can be integrated, but BGA deforms during SMT processes because melted solder bumps cannot support the package weight
Solution Approach 1:
The package lid and mold compound structure are designed to provide mechanical support that counteracts the package's own weight, distributing loads away from the solder bumps during SMT processing. This prevents excessive stress on the BGA while maintaining high chip integration density.
Solution Approach 2:
The mold compound and package lid are designed to provide pre-existing mechanical support and cushioning to the BGA structure before SMT processing occurs. This protective structure prevents solder bump deformation during subsequent welding operations by absorbing and distributing thermal and mechanical stresses.
4Productivity
If package size and weight increase, then more chips can be integrated, but adjacent solder bumps touch causing bridging and electrical short-circuits
Solution Approach 1:
The structural support from the mold compound and package lid counteracts gravitational and thermal loads, preventing solder bumps from deforming outward and touching adjacent bumps. This maintains electrical isolation between adjacent solder joints while enabling high integration density.
Solution Approach 2:
The encapsulating mold compound provides pre-positioned mechanical cushioning that maintains proper spacing between solder bumps throughout the SMT process. This prevents bridging and electrical short-circuits by ensuring solder bumps remain separated even under thermal expansion and gravitational loads during high-density integration.
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 spacer structure effectively prevents solder ball bridging and electrical short-circuits by maintaining a consistent gap and distributing pressure uniformly, ensuring reliable surface mounting and operation at higher temperatures without substantial deformation.
Implementation Method 1
mismatched coefficients of thermal expansion
Implementation Method 2
distributing pressure uniformly
Data Source
AI summary
A semiconductor package includes a semiconductor chip disposed over a first main surface of a first substrate, a package lid disposed over the semiconductor chip, and spacers extending from the package lid through corresponding holes in the first substrate. The spacers enter the holes at a first main surface of the first substrate and extend beyond an opposing second main surface of the first substrate.