Leadframe Strap Locking Feature for Transfer Molded IC Packages
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional IC package molding processes face issues such as mold gate blockage and package failures due to insufficient adhesion between the encapsulant and the leadframe straps, leading to decreased productivity and increased downtime for mold cleaning or replacement.
Innovation Solution
Incorporating locking features such as grooves, V-grooves, rabbeted edges, beveled edges, or downset strap portions in the leadframe straps to enhance the bond between the encapsulant and the straps during transfer molding, forming strap locks that improve the mechanical integrity of the package array and reduce mold gate blockage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional side-gate systems are used for transfer molding, then the molding process is simple and widely used, but mold gates become blocked by cured encapsulant and productivity decreases
Solution Approach 1:
The patent segments the encapsulant flow path by introducing manifold channels that distribute molten encapsulant to multiple cavities simultaneously, rather than relying on a single gate system. This segmentation prevents blockage in any single gate while maintaining multiple active flow paths, thus preserving productivity without sacrificing manufacturing simplicity
Solution Approach 2:
The patent introduces an intermediary manifold structure that acts as a distribution network between the encapsulant source and individual cavity gates. This manifold system mediates the flow distribution, ensuring that encapsulant reaches multiple cavities concurrently through balanced pressure distribution, preventing gate blockage while maintaining process simplicity
2Ease of manufacture
If encapsulant is injected through lateral gates in series, then the molding process is conventional and easy to implement, but cavities farther from the source are filled later and mold gate blockage occurs
Solution Approach 1:
The patent segments the single-series gate system into multiple parallel injection paths through the manifold structure. Each cavity receives encapsulant through its own dedicated channel from the manifold, enabling simultaneous filling of all cavities with uniform pressure distribution, thus achieving precise manufacturing without complex implementation
Solution Approach 2:
The patent transitions from a one-dimensional series gate arrangement to a two-dimensional manifold distribution network. This dimensional change allows encapsulant to be distributed across multiple cavities simultaneously through the manifold's multi-channel structure, achieving uniform filling across all cavities while maintaining ease of implementation
3Device complexity
If straps are insufficiently adhered to cured encapsulant, then the leadframe structure is simple, but package failures such as breaks and cracks occur during extraction
Solution Approach 1:
The patent introduces curved or rounded features on the strap surfaces that contact the encapsulant. These curved geometries increase the surface area and create mechanical interlocking effects, enhancing adhesion between the strap and cured encapsulant without significantly increasing leadframe structure complexity
Solution Approach 2:
The patent applies localized adhesion-enhancing features specifically at the strap-encapsulant interface regions where bonding is critical. These local modifications (such as surface textures or geometric features) concentrate the adhesion improvement where needed most, during extraction and handling, without adding complexity to the entire leadframe structure
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 implementation of strap locks strengthens the IC package arrays, reduces the likelihood of encapsulant separation during extraction, and enhances handling and singulation processes, thereby improving manufacturing efficiency and reducing package damage.
Implementation Method 1
Incorporating locking features such as grooves, V-grooves, rabbeted edges, beveled edges, or downset strap portions in the leadframe straps to enhance the bond between the encapsulant and the straps during transfer molding, forming strap locks that improve the mechanical integrity of the package array
Data Source
AI summary
The invention discloses integrated circuits (ICs), molded IC packages, and to leadframe arrays, package arrays and methods for their manufacture. Leadframe arrays and package arrays used for the manufacture of IC packages by transfer molding processes include a locking feature adapted for encapsulation. The locking feature is situated in a strap of the leadframe array overlying a gate between mold cavities. The strap lock formed by curing encapsulant in the locking feature of the strap strengthens the resulting package array and provides improved mold extraction and handling characteristics.