Interleaved J-Lead and Gull Wing Lead Frame for IC Packaging
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Solution Overview
Problem
The existing lead frame designs for integrated circuit packaging face issues with lead pitch reduction and electrical short circuits due to bending and deformation during the molding process, which can cause tape separation and contact between adjacent leads.
Innovation Solution
A lead frame design with interleaved J-leads and Gull Wing leads, where the second leads have a down-set portion that maintains the inner lead area in the same plane during molding, preventing separation from the tape and ensuring proper spacing and electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the lead pitch is reduced to increase the number of leads around the package body, then the lead density increases, but the leads are more prone to bending and contacting with adjacent leads during the molding process
Solution Approach 1:
The lead frame is pre-formed with J-leads and Gull Wing leads in their final spatial configurations before the molding process. The interleaved arrangement is established in advance, so that during molding, the leads maintain their predetermined spacing and orientation, preventing contact between adjacent leads even at reduced pitch
Solution Approach 2:
The lead frame utilizes three-dimensional spatial arrangement by interleaving J-leads and Gull Wing leads in both horizontal and vertical dimensions. This multi-dimensional configuration allows leads to be closely spaced while maintaining adequate clearance through vertical separation, effectively increasing lead capacity without compromising reliability
2Manufacturing precision
If the mold tooling presses on the outer lead portion to vertically space Gull Wing leads and J-leads, then the vertical spacing between lead types is achieved, but the tape separates from the leads causing potential short circuits
Solution Approach 1:
Different regions of the lead frame are given different structural properties: J-leads have a downward bend configuration while Gull Wing leads have an outward bend configuration. This local differentiation allows each lead type to respond appropriately to molding pressure, with J-leads being pressed downward and Gull Wing leads being pressed outward, achieving vertical spacing without tape separation
Solution Approach 2:
The lead frame structure is designed to preemptively counteract the harmful effects of molding pressure. By pre-configuring the interleaved arrangement and appropriate lead bends, the design prevents tape separation and lead contact before they can occur during the molding process, eliminating the need for corrective measures
Data Source
AI summary
A lead frame for a packaged integrated circuit (IC) device has alternating first and second leads that protrude from a package body in respective first and second planes, where the second plane is parallel to and below the first plane. The first leads are formed into Gull Wing shaped leads and the second leads are formed into J-shaped leads. Inner lead portions of the first and second leads are maintained in the first plane with a tape. An inner lead portion of each of the second leads, proximate to and extending to the outer lead portion, is down-set, so that when the outer lead portion is pressed down by a mold tool to locate the outer lead portion of the second leads in the second plane, the inner lead portion of the second leads is maintained in the first plane and does not separate from the tape.