Wafer Package Overmolding That Preserves Grating Coupler Access
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Solution Overview
Problem
Maintaining optical pathways through circuit packages is challenging, particularly in manufacturing and implementing IC architectures, as overmolding can obscure access to optical regions.
Innovation Solution
The use of a sacrificial die is employed to create an optical window by pre-cutting and removing a portion of the die before overmolding, ensuring access to optical regions like grating couplers through a void in the overmold layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If overmolding is applied to protect and encapsulate circuit package components, then mechanical protection and structural integrity are improved, but access to optical regions is lost
Solution Approach 1:
The overmold is segmented into two distinct parts: a first overmold that provides mechanical protection for electrical components, and a second overmold that is transparent and provides optical access to the optical window. This segmentation allows each overmold segment to fulfill its specific function without interfering with the other.
Solution Approach 2:
The patent applies different material properties to different regions of the overmold structure. The first overmold uses materials optimized for mechanical protection (epoxy, polyimide, or polyester), while the second overmold uses transparent materials (epoxy, polyimide, or polyester with added transparency) to enable optical transmission. This local differentiation of material properties resolves the contradiction between protection and optical access.
2Ease of operation
If a sacrificial die is used to create an optical window by removing material, then optical access is improved, but manufacturing complexity increases
Solution Approach 1:
The sacrificial die is pre-positioned on the substrate at the desired optical window location before the overmolding process begins. This preliminary placement allows the die to serve as a template and protective element during subsequent manufacturing steps, simplifying the overall process by combining multiple functions (alignment, protection, and window definition) into a single preparatory action.
Solution Approach 2:
The sacrificial die acts as an intermediary element that facilitates the creation of the optical window without being part of the final product. It mediates between the substrate and the overmold materials, protecting the optical region during processing and enabling precise window formation through selective removal after curing, thereby managing manufacturing complexity.
3Use of energy by moving object
If the optical region is exposed on the wafer surface, then photonic signal transmission is improved, but the wafer becomes vulnerable to damage and contamination
Solution Approach 1:
The patent employs thin film overmold materials (epoxy, polyimide, or polyester) that conformally coat the substrate and optical components. These thin films provide protective encapsulation while maintaining optical transmission properties, thus protecting the exposed optical region from damage and contamination without blocking photonic signal transmission.
Solution Approach 2:
The overmold structure uses composite material systems combining different polymer materials with specific optical and mechanical properties. The transparent overmold materials are selected to match the optical requirements (transmission wavelength, refractive index) while providing mechanical protection, creating a composite solution that simultaneously addresses both photonic transmission and protection needs.
Data Source
AI summary
The present disclosure relates to packaging techniques in connection with packaging electrical and optical components within circuit packages. For example, one or more examples described herein involve techniques for packaging an electro-photonic circuit while preserving access to a grating coupler, which may involve using a sacrificial die in conjunction with a unique overmolding process.