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Protruded Semi-cylinder Lead End Shape for Inspectable Solder Joint QFN

IP.com Disclosure Number: IPCOM000244354D
Publication Date: 2015-Dec-04
Document File: 5 page(s) / 125K

Publishing Venue

The IP.com Prior Art Database

Abstract

Customers are requiring inspectable solder joints on QFN packages, where inspection is done via AOI (Automated Optical Inspection). Current QFN lead end inspectable solder joint design is step cut and dimple (or dimple + filled solder) design. The width of plated area in the dimple is approximately half of the lead width. Whereas in Step cut, plating spans the full lead width, but plating height is only half lead end height. This idea (of Protruded Semi-cylinder Lead End Shape) can realize lead frame and assembly method for QFN package that allows for full lead end solder joint design using PPF lead frame.

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Protruded Semi-cylinder Lead End Shape for Inspectable Solder Joint QFN

Abstract: 

Customers are requiring inspectable solder joints on QFN packages, where inspection is done via AOI (Automated Optical Inspection). Current QFN lead end inspectable solder joint design is step cut and dimple (or dimple + filled solder) design. The width of  plated area in the dimple is approximately half of the lead width. Whereas in Step cut, plating spans the full lead width, but plating height is only half lead end height. This idea (of Protruded Semi-cylinder Lead End Shape) can realize lead frame and assembly method for QFN package that allows for full lead end solder joint design using PPF lead frame.

Body:   

  1. The protruded lead end is in the shape of semi-cylinder, which makes solder build up easier and ends with larger light reflection plane, which improves the SMT AOI (Auto optical inspection) detection.
    1. AOI tool is installed on top of the PCB board, so the detection lights signal injected to the solder joints (wedge shaped from side view) of traditional solder visible QFN lead/pad design encounters more diffuse reflection which weakens the reflection signal.
    2. Current innovation creates a larger flat surface(perpendicular to the light path) to reflect more detection light signal when solder joint quality is good, this will make the AOI detection more effective on soldering quality variation during SMT process.
  2. The protruded semi-cylinder shape lead without mold compound in between...