MLP Gutter Via for Solder Short Prevention
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Solution Overview
Problem
Solder shorts are increasingly common in Molded Laser Package (MLP) packages due to insufficient through mold via volume, leading to high pressure and moisture entrapment, which causes solder balls to expand and short against each other.
Innovation Solution
Integrating gutters adjacent to through mold vias in the molding layer, which provide a pressure relief path by extending vertically from the top surface to a depth equal to or less than half the vertical diameter of the solder balls, allowing for expansion without bridging, and optionally featuring tiered depths for enhanced relief.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through mold via volume is increased to prevent moisture entrapment and pressure buildup, then solder short reliability improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The through mold via structure is segmented into two functional parts: the via hole itself and the integrated gutter structure. The gutter acts as a separate pressure relief chamber connected to the via, allowing moisture and pressure to be managed independently from the electrical connection function. This segmentation enables the via to maintain sufficient volume for reliability while the gutter provides additional pressure relief capacity.
Solution Approach 2:
The gutter structure is nested within or adjacent to the through mold via structure, creating a compact integrated feature. The gutter is positioned to receive and contain pressure relief material that expands during reflow, preventing this expansion from affecting adjacent solder balls. This nesting approach increases functionality without proportionally increasing overall device complexity.
2Productivity
If tighter top ball pitch is used to increase component density, then productivity improves, but solder shorts increase due to insufficient via volume and pressure buildup
Solution Approach 1:
The solution addresses the two-dimensional pitch constraint by adding a vertical dimension through the gutter structure. The gutter extends vertically from the top surface of the molding compound to a depth that provides adequate pressure relief volume. This vertical expansion allows tighter horizontal pitch while maintaining sufficient volume for pressure and moisture management, enabling higher component density without sacrificing reliability.
Solution Approach 2:
The via structure is segmented to separate the electrical conduction function from the pressure relief function. The gutter portion specifically handles pressure and moisture relief, allowing the via to maintain smaller horizontal dimensions for tighter pitch while the gutter provides the necessary vertical volume for reliability.
3Length of stationary object
If thinner molding layer is used to reduce package thickness, then device miniaturization improves, but pressure relief capability deteriorates due to insufficient via volume
Solution Approach 1:
Instead of uniformly increasing the overall package thickness or via volume throughout the structure, the gutter is strategically positioned at specific locations where pressure relief is most critical. The gutter depth and volume are locally optimized to provide adequate pressure relief capability while maintaining the overall thin package profile. This local quality approach allows pressure relief functionality to be enhanced without proportionally increasing overall device dimensions.
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 gutters effectively reduce the risk of solder shorts by providing a pressure relief path, enabling tighter bump pitch and thinner packages, improving process margins and flexibility in surface mount technology (SMT) manufacturing.
Implementation Method 1
the solder balls 102 to expand and flow over a wall 109 in the molding layer, which separates the solder balls 102, causing a short
Data Source
AI summary
Improved Molded Laser Package (MLP) Packages which include a relief path for pressure and reduces the risk of shorting adjacent solder balls are provided. The MLP packages may include a gutter integrally connected to one or more through mold vias allowing a path to relieve pressure created when moisture gets entrapped in through mold vias, during the manufacturing process, while also reducing the risk of solder shorts between adjacent solder balls located in the through mold vias. Additionally, MLP packages which include gutters integrally connected to one or more through mold vias may enable tighter bump pitch and thinner packages. As a result, process margins and risks associated with surface mount technology (SMT) may be improved and provide more flexibility on inventory staging.