Stepped SMPD Lead Structure for Bonding Stability and Positioning
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Solution Overview
Problem
Current surface mount power device (SMPD) packaging processes are susceptible to issues like lead frame tilt, warpage, micro-bouncing effect, and weak bonding force, which affect thermal performance and reliability.
Innovation Solution
A surface mount power device design featuring a ceramic insulating core with patterned metal layers and stepped features, where bond wires are connected to raised portions instead of lead terminals, and Y-shaped lead terminals are bonded to peripheral portions, enhancing stability and positioning precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional lead frame bonding is used in SMPD packaging, then the bonding process is simple, but lead frame tilt and warpage occur causing micro-bouncing effect and weak bonding force
Solution Approach 1:
The patent introduces a stepped feature with a raised portion that creates a vertical dimension difference between the bonding surface and the lead terminal. The bond wire is bonded to the raised portion at a higher elevation, while the lead terminal remains at the base level for PCB mounting. This dimensional separation eliminates the micro-bouncing effect by providing a stable bonding surface that is not affected by lead frame tilt or warpage, thereby improving both bonding force and positioning precision simultaneously.
2Manufacturing precision
If Y-shaped lead terminal structure is used, then positioning precision is improved, but device complexity increases
Solution Approach 1:
The patent employs an asymmetric Y-shaped lead terminal structure where one branch of the Y is longer than the other. This asymmetric design provides inherent positional reference during installation, enabling precise alignment and positioning on the PCB without requiring additional alignment features or complex positioning mechanisms. The asymmetry converts a potentially complex positioning problem into a simple geometric solution, improving manufacturing precision while maintaining relatively simple device structure.
Data Source
AI summary
A surface mount power device includes a substrate composed of an insulating core and a patterned metal layer, wherein the patterned metal layer includes a base island area and a lead area; a stepped feature is provided in the lead area, wherein the stepped feature includes a raised portion and a peripheral portion, and the peripheral portion is lower than the raised portion; a conductive material layer on the peripheral portion of the stepped feature; a semiconductor die attached onto the patterned metal layer within the base island area; a lead including a lead terminal bonded to the peripheral portion of the stepped feature through the conductive material layer; a bond wire connecting the semiconductor die to the raised portion of the stepped feature; and an encapsulant covering the substrate, the stepped feature, the semiconductor die, and the bond wire, and partially covering the lead.