Molded BGA Spacer for Coplanarity Support and Pad Density
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Solution Overview
Problem
The increasing size and pitch of ball grid array (BGA) packages lead to coplanarity and warpage issues, which affect surface mount technology (SMT) yields and reduce functional density due to the need for depopulating BGA pads to accommodate standard-sized solid metal spacers.
Innovation Solution
A customizable molded spacer with a core covered by an insulating material, designed to fit onto a single BGA pad, allowing placement within the BGA array without interfering with adjacent pads, and is produced through an overmolding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard-sized solid metal spacers are used to prevent solder bridging, then reliability is improved, but functional density deteriorates due to depopulation of multiple BGA pads
Solution Approach 1:
The spacer size is changed from standard fixed dimensions to customizable dimensions that match the BGA ball diameter. This allows the spacer to occupy only the space of a single depopulated pad rather than requiring multiple pads to be depopulated, thereby maintaining functional density while still preventing solder bridging effectively
Solution Approach 2:
The spacer is designed with specific local dimensions tailored to the BGA ball diameter at each location. This localized customization allows the spacer to fit precisely on individual depopulated pads within the BGA array, enabling internal region placement without interfering with adjacent functional pads, thus preserving overall functional density
2Productivity
If larger BGA packages are used to accommodate higher I/O, then I/O capacity is improved, but coplanarity and warpage worsen
Solution Approach 1:
The custom-sized spacers act as intermediary elements between the BGA package and the PCB. By placing these spacers at strategic locations on the PCB, they provide localized support that helps maintain coplanarity and reduce warpage in larger BGA packages, enabling higher I/O capacity without compromising package stability
3Productivity
If BGA pitch is reduced to less than 1mm to increase I/O density, then I/O capacity is improved, but signal integrity worsens due to resonance effects
Solution Approach 1:
The spacers are extracted and placed specifically in internal regions of the BGA array where resonance effects are most problematic. By removing solder bridges in these critical areas and providing mechanical support, the spacers mitigate resonance effects that would otherwise degrade signal integrity in high-density BGAs with sub-1mm pitch
Data Source
Figure 1A~1C
Figure 2A~3
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AI summary
Methods, systems, and apparatus, for a molded spacer. In an aspect, a spacer comprises a core defining a top surface, a bottom surface, and one or more side surfaces; a molded covering that covers at least the top surface of the core, the molded covering comprising an insulation material, wherein the spacer has a cross sectional size to fit onto a depopulated connection pad of a ball grid array of a circuit board without interfering in a reflow soldering operation for solder balls placed on connection pads immediately adj acent to the depopulated connection pad.