Bump Chip Carrier Pressure Sensor Assembly
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Solution Overview
Problem
Existing pressure sensor packaging techniques are expensive and have reliability issues, particularly in creating smaller integrated circuits for modern devices, and are peripheral non-pressure sensor wire bond types, which are not suitable for high-density packaging.
Innovation Solution
A method of assembling a pressure sensor device using a metal sheet with pre-formed exposed conductive bumps integral to the carrier, formed through a build-up process, eliminating the need for additional solder ball attach and incorporating an insulating layer for stress relief, which reduces assembly costs and enhances reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing pressure sensor packaging techniques are used, then the packaging can be completed, but the cost is high and reliability issues occur
Solution Approach 1:
The packaging process is segmented into distinct stages: forming the lead frame structure, attaching the pressure sensor die, applying molding compound, and forming solder balls. This segmentation allows each stage to be optimized independently, improving reliability while controlling costs through standardized processes.
Solution Approach 2:
The lead frame is pre-formed with specific structural features (legs, body, and contact areas) before die attachment. The molding compound is applied before solder ball formation. These preliminary actions ensure proper positioning and protection early in the process, preventing reliability issues later while avoiding costly rework.
2Productivity
If peripheral non-pressure sensor wire bond type packages are used, then the packaging can be completed, but high-density packaging is not achieved
Solution Approach 1:
The package transitions from a peripheral wire bond configuration to a three-dimensional bump chip carrier structure. The lead frame extends in multiple dimensions with legs projecting from the body, and solder balls are formed at multiple contact points, enabling high-density interconnections without increasing planar complexity.
Solution Approach 2:
The lead frame serves multiple functions simultaneously: it provides mechanical support, electrical interconnection, and mounting structure for the pressure sensor die. The molding compound provides both protection and structural integrity. This multi-functionality reduces the number of separate components needed, achieving high density without excessive complexity.
3Reliability
If additional solder ball attach process is used, then electrical connections can be established, but assembly costs increase and solder drop issues occur
Solution Approach 1:
The lead frame structure is merged with the solder ball formation process. The lead frame body and legs are formed integrally, and solder balls are applied directly to the contact areas during the molding compound application stage. This merging eliminates the need for separate solder ball attach equipment and processes, reducing costs while ensuring reliable connections through controlled application.
Solution Approach 2:
The molding compound acts as an intermediary material that simultaneously protects the pressure sensor die, provides structural support, and facilitates solder ball placement. By applying the molding compound before solder ball formation, the process ensures proper positioning and reduces solder drop issues while integrating multiple functions into a single operation.
Data Source
AI summary
A pressure sensor device is assembled by forming cavities on a surface of a metal sheet and then forming an electrically conductive pattern having traces and bumps over the cavities. An insulating layer is formed on top of the pattern and then processed to form exposed areas and die attach areas on the surface of the metal sheet. The exposed areas are plated with a conductive metal and then electrically connected to respective ones of the bumps. A gel is dispensed on the die attach areas and sensor dies are attached to respective die attach areas. One or more additional semiconductor dies are attached to the insulating layer and bond pads of these dies are electrically connected to the exposed plated areas. A molding compound is dispensed such that it covers the sensor die and the additional dies. The metal sheet is removed to expose outer surfaces of the bumps.