Semiconductor Package Cavity Structure for Lead Density
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Solution Overview
Problem
Current semiconductor chip packaging technologies, such as Quad Flat No Lead (QFN), face challenges in scalability of lead density, package size reduction, and maintaining sufficient mold locking and surface mounting reliability, particularly in increasing lead density and reducing package height.
Innovation Solution
A semiconductor package design featuring a die pad with a cavity structure and sloped portions, along with a method using a metal carrier plate to form leads and a package body that covers the chip and leads, enhancing adhesion and mold locking while allowing for scalable lead density and reduced package height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If QFN packaging technology is used to increase lead density, then lead density is improved, but scalability beyond two rows of leads is limited
Solution Approach 1:
The leadframe is segmented into a reusable portion and a disposable portion, allowing the reusable portion to be retained across multiple packaging cycles. This segmentation enables scalability beyond the traditional two-row limitation of QFN packages by allowing incremental addition of lead rows while maintaining structural integrity through the reusable portion.
2Length of stationary object
If package height is reduced to decrease package size, then package size is improved, but mold locking of leads becomes insufficient
Solution Approach 1:
The invention introduces sloped portions on the leads that extend laterally outward from the package body, compensating for reduced vertical height. These sloped portions create lateral engagement with the mold compound, providing sufficient mold locking through a different dimensional approach (lateral rather than vertical engagement) while maintaining reduced package height.
3Length of stationary object
If package height is reduced to decrease package size, then package size is improved, but surface mounting reliability becomes insufficient
Solution Approach 1:
The sloped portions extending laterally from the package body provide enhanced surface for solder joint formation during surface mounting. By distributing the mounting interface laterally rather than relying solely on vertical height, the invention maintains reliable surface mounting attachment while achieving reduced package height.
Data Source
AI summary
A semiconductor package and related methods are described. In one embodiment, the package includes a die pad, a plurality of leads, a chip, and a package body. The die pad includes: (1) a peripheral edge region defining, a cavity with a cavity bottom including a central portion; (2) an upper sloped portion; and (3) a lower sloped portion. Each lead includes an upper sloped portion and a lower sloped portion. The chip is disposed on the central portion of the cavity bottom and is coupled to the leads. The package body is formed over the chip and the leads, substantially fills the cavity, and substantially covers the upper sloped portions of the die pad and the leads. The lower sloped portions of the die pad and the leads at least partially extend outwardly from a lower surface of the package body.