Leadframe Package Stand for Vertical Stacking and Fine Pitch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge lies in converting area array CSP type packages into leadframe type packages with fine pitches and high I/O counts, as existing methods struggle with mass production of stamped or etched leadframes with pitches less than 200 um and greater than 50 I/Os, and achieving vertical stacking without increasing board area or affecting existing footprints.
Innovation Solution
A leadframe package stand with an area array grid pattern of conductive traces is used, allowing direct connection of flip chip ICs or wafer level packages to inner leads without intermediate wire bonds, utilizing sacrificial tie-bars or adhesive tape to maintain lead alignment during molding, and enabling vertical stacking by forming a cavity in the mold body to accommodate bare chips or wafer level packages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If stamped or etched leadframes are used with fine pitch (less than 200 um) and high I/O (greater than 50), then manufacturing precision is improved, but device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The leadframe is divided into multiple functional segments: outer leads for PWB connection, inner leads for IC bonding pad connection, and conductive traces connecting them. This segmentation allows each part to be optimized independently - outer leads maintain standard pitch for existing PWB compatibility, while inner leads achieve fine pitch for high-density IC connections without requiring the entire leadframe structure to be re-engineered
Solution Approach 2:
The patent transitions from traditional two-dimensional leadframe layouts to a three-dimensional configuration with conductive traces that route through multiple layers and dimensions. This allows inner leads to connect to IC bonding pads in an area array format while outer leads maintain standard perimeter arrangements, effectively adding a dimensional aspect to the leadframe design that resolves the conflict between fine pitch requirements and manufacturing complexity
2Adaptability or versatility
If area array CSP packages are converted to leadframe type packages, then adaptability is improved, but manufacturing time and complexity increase
Solution Approach 1:
The leadframe package stand is designed with universal functionality to accommodate multiple package types - it can receive both area array CSP packages and wafer level packages, and support both wire bonding and flip chip bumping technologies. The conductive traces are configured to interface with standard IC bonding pads, making the leadframe compatible with various IC formats without requiring custom designs for each package type
Solution Approach 2:
The patent employs preliminary actions in the manufacturing process by pre-forming the conductive traces and inner leads in the leadframe before IC assembly, and by using mold cavities that are pre-configured to hold the IC in the correct position. This preliminary preparation of the leadframe structure and molding tools eliminates time-consuming alignment and positioning steps during the actual IC assembly process
3Area of stationary object
If vertical stacking is implemented to increase assembly density, then space efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements vertical stacking by nesting one package directly above another on the same PWB footprint. The leadframe package stand is designed to receive the IC package vertically, with the mold cavity positioned to accommodate the IC body. This nesting arrangement allows multiple packages to occupy the same board area by stacking them in the vertical dimension, effectively reducing the board footprint while maintaining precise alignment through the molded structure
Data Source
AI summary
A method is disclosed for making a leadframe package stand having application in semiconductor packaging and microelectronic assembly in which an IC device (e.g., a bare chip IC, a wafer level package, or a chipscale package) is received for electrical connection to a PWB or for vertical package over package stacking. Electrically conductive leadframe traces are arranged in an area array circuit pattern between outer leads at the periphery of the mold body of a leadframe for connection to the PWB to inner leads for connection to the IC device. The inner lead tips terminate at each side of the IC device in groups of parallel aligned rows and columns to facilitate connection to the IC device without using intermediate bonding wires. Prior to molding, the inner leads of the conductive traces are secured by sacrificial tie-bars or adhesive tape to prevent movement of the inner leads and possible short circuits during molding. A cavity is formed in the mold body during molding so as to lie above the inner leads. After molding, the sacrificial tie-bars are separated from the inner leads, and the IC device is located in the cavity to be assembled to the leadframe to complete a leadframe package.