IC package with connection pads for die
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Solution Overview
Problem
Conventional IC packages face challenges in forming reliable solder joints due to cracking, which leads to failure, particularly in fine-pitch applications where spacing between connections is narrow.
Innovation Solution
The introduction of copper pillars on connection pads, extending normal to the interconnect surface, enhances solder joint formation by providing mechanical stability and reducing thermal stress, using a process involving photoresist deposition, copper electroplating, and solder reflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional interconnect structures are used for mounting semiconductor dies, then the packaging process is simple, but solder joints crack under thermal stress leading to package failure
Solution Approach 1:
The interconnect structure is segmented into multiple functional layers: a base interconnect layer and protruding pillars extending from its surface. This segmentation allows the pillars to specifically bear thermal stress while the base layer maintains electrical connectivity, resolving the contradiction between reliability and complexity by distributing functions across separate structural elements.
Solution Approach 2:
The invention transitions from a planar interconnect surface to a three-dimensional structure with pillars extending vertically from the surface. This dimensional change creates additional structural support in the vertical direction, enabling the pillars to absorb thermal expansion stresses that would otherwise cause solder joint cracking, thereby improving reliability without significantly complicating the overall device architecture.
2Productivity
If fine-pitch applications with narrow spacing between connections are used, then device density increases, but solder joint cracking becomes more prevalent
Solution Approach 1:
The pillars are strategically positioned at specific locations where solder joints are most vulnerable to cracking, particularly in fine-pitch regions. This local quality approach concentrates structural reinforcement exactly where needed, allowing high device density to be maintained while selectively improving solder joint integrity at critical positions without requiring universal structural changes.
3Ease of manufacture
If traditional flat connection pads are used, then manufacturing is simpler, but thermal stress causes crack propagation and delamination
Solution Approach 1:
The pillars are formed on the interconnect surface before the soldering process, creating a pre-reinforced structure that is ready to withstand thermal stresses during subsequent manufacturing steps. This preliminary action ensures that crack propagation is prevented from the outset, maintaining both manufacturing simplicity and structural strength throughout the fabrication process.
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 copper pillars improve the structural integrity and electrical performance of IC packages by preventing crack propagation and delamination, reducing strain and shear stress during thermal cycles, and ensuring reliable connections.
Implementation Method 1
enhances solder joint formation by providing mechanical stability and reducing thermal stress
Implementation Method 2
A portion of the solder bumps flow over the pillars
Implementation Method 3
preventing crack propagation and delamination, reducing strain and shear stress during thermal cycles
Data Source
AI summary
An IC (integrated circuit) package includes a first interconnect. The first interconnect includes a first surface having connection pads. The connection pads include pillars extending in a direction normal to the first surface and a second surface opposing the first surface having connection pads for leads. The IC package also includes a second interconnect including the leads mounted on the connection pads of the second surface of the first interconnect and a die mounted with solder bumps on the connection pads of the first surface of the first interconnect. A portion of the solder bumps flow over the pillars.