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Create High Pin Count Leaded Surface Mount Semiconductor Packages with Metal Etching Process

IP.com Disclosure Number: IPCOM000201570D
Publication Date: 2010-Nov-15
Document File: 5 page(s) / 174K

Publishing Venue

The IP.com Prior Art Database

Abstract

Proposed disclosure defines a process to create high pin count leaded surface mount package with good manufacturability and low cost. The proposed method is suitable for gull-wing type of leaded packages rather than J-shape leaded packages. With selectively plated leadframe and metal etching as only one process added to standard assembly flow of gull-wing leaded packages, additional fine pitch lead terminals could be created at the bottom of package body in single row, multiple rows or irregular layout beside the leads with standard leaded packages. It is also possible to create the leads in irregular shapes. The proposed disclosure could increase lead density to shrink the package size and improve the electrical performance, for instance the higher speed. It also allows some special features to be created, for instance the shielding or ground structure at the bottom of package.

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Create High Pin Count Leaded Surface Mount Semiconductor Packages with Metal Etching Process

Abstract:

Proposed disclosure defines a process to create high pin count leaded surface mount package with good manufacturability and low cost. The proposed method is suitable for gull-wing type of leaded packages rather than J-shape leaded packages. With selectively plated leadframe and metal etching as only one process added to standard assembly flow of gull-wing leaded packages, additional fine pitch lead terminals could be created at the bottom of package body in single row, multiple rows or irregular layout beside the leads with standard leaded packages. It is also possible to create the leads in irregular shapes. The proposed disclosure could increase lead density to shrink the package size and improve the electrical performance, for instance the higher speed. It also allows some special features to be created, for instance the shielding or ground structure at the bottom of package.

Problem to Solve:

Current leaded surface mount packages are mature, reliable and low cost, however, there are limitations to support high pin count products due to low lead density. Some new processes were developed with half cutting process to create leads at bottom of package body, but the critical manufacturability issues are introduced with bottom lead creation. The major issues include resin bleed, lead shorting and bonding wire damage, metal burs on the lead and poor inspectability. All those major manufacturing issues lead to difficulties of process control, bad quality and significant yield loss.

About the Solution:

The proposed method uses specially designed leadframe with selective plating and etching process after encapsulation to create the leads at bottom of package body. The only additional process added than standard gull-wing lead package assembly is metal etching post encapsulation. The plating layers act as a mask to protect the base metal to be etched off during etching process. The areas are not covered by plating layers will be exposed to etchant to be removed during the etching process. Therefore, while the selective plating defines a pattern of lead terminals on both top and bottom sides of die pad, the leads will be formed and isolated from die pad after etching process. Figure 1 is one embodiment having selective plating defines the die pad and lead terminals around die pad shown as view A. Half etch could be made at unplated areas on the top side of leadframe (encapsulation side) to have better lock between mold compound and leadframe. It also makes the metal etching process easier. The die pad and lead terminals are formed after etching process shown as view B. The selectively plated leadframe is a standard technology available with...