Lead Frame Baffles for Semiconductor Molding Compound Flow Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor packaging processes face issues with uneven resin flow in mold cavities due to variations in mold cavity configurations, semiconductor die shapes, and lead frame orientations, leading to voids, knit lines, and pinholes, which compromise packaging integrity and heat transfer.
Innovation Solution
The introduction of baffles in lead frames and substrates to selectively impede and redirect the flow of molding compound, ensuring uniform resin distribution across the top and bottom surfaces of semiconductor dice, thereby modifying the hydraulic characteristics of the flowable packaging material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional molding processes are used without flow control structures, then the packaging process is simple and fast, but uneven resin flow occurs leading to voids, knit lines, and pinholes
Solution Approach 1:
The mold cavity is segmented into multiple regions using flow control structures (baffles, ribs, or protrusions) that divide the resin flow path. This segmentation ensures that resin flows more uniformly across different areas of the semiconductor die, preventing void formation and improving packaging integrity without requiring complete redesign of the molding process.
Solution Approach 2:
Flow control structures act as intermediary elements between the resin injection point and the semiconductor die. These structures (such as baffles or ribs) mediate the resin flow by creating controlled flow paths, ensuring uniform distribution of molding compound around the die and lead frame, thereby eliminating defects like knit lines and pinholes.
2Reliability
If resin flow is allowed to follow the path of least resistance around the sides of the die stack, then the molding process is simple, but voids form at the top and bottom of the die stack
Solution Approach 1:
The lead frame is modified with localized flow control features (such as varied tie bar configurations or localized baffles) that create different flow resistance characteristics in different areas. This local modification ensures that resin flows uniformly over and under the die stack rather than shortcutting around the sides, preventing void formation at critical locations.
Solution Approach 2:
Flow control structures extend the resin flow path from a primarily two-dimensional lateral flow around the die stack to include controlled three-dimensional flow patterns. By introducing vertical or angled flow paths through baffles or ribs, the resin is forced to flow over and under the die stack, ensuring complete encapsulation and eliminating voids.
3Manufacturing precision
If mold cavity configurations and lead frame orientations are fixed, then manufacturing is straightforward, but resin flow uniformity cannot be optimized for different die shapes and sizes
Solution Approach 1:
The flow control structures are designed with adjustable or flexible characteristics that allow them to adapt to different die configurations. For example, baffles may be positioned at variable distances from the die, or rib heights may be adjusted based on die thickness, enabling the same mold cavity to accommodate different die shapes and sizes while maintaining uniform resin flow.
Solution Approach 2:
The flow control structures utilize variable geometric parameters (such as baffle height, rib thickness, or protrusion length) that can be modified based on the specific die configuration. By changing these parameters, the resin flow characteristics are optimized for each die type, ensuring uniform distribution regardless of die shape or size variations.
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
This approach enhances the uniformity of resin coverage, reducing voids and defects in the encapsulant, thereby improving the packaging integrity and heat transfer characteristics of semiconductor devices.
Implementation Method 1
a baffle, such as a tie bar baffle or paddle baffle, may be attached to a support or conductive member and arranged substantially transverse to a flow path of resin
Data Source
AI summary
Flow diverting structures for preferentially impeding, redirecting or both impeding and redirecting the flow of flowable encapsulant material, such as molding compound, proximate a selected surface or surfaces of a semiconductor die or dice during encapsulation are disclosed. Flow diverting structures may be included in or associated with one or more portions of a lead frame, such as a paddle, tie bars, or lead fingers. Flow diverting structures may also be inserted into a mold in association with semiconductor dice carried on non-lead frame substrates, such as interposers and circuit boards, to preferentially impede, redirect or both impede and redirect the flow of molding compound flowing between and over the semiconductor dice.