Etching a substrate: processes – Forming or treating josephson junction article
Patent
1994-11-23
1996-12-03
Powell, William
Etching a substrate: processes
Forming or treating josephson junction article
216 65, 257673, 437220, H01L 2100, B44C 122, C23F 100
Patent
active
055804667
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a metal plate processing method capable of finely processing metal plates into a satisfactory configuration, a method of processing lead frames utilizing the metal plate processing method, the lead frame itself, a method of manufacturing semiconductor devices using such lead frames, and the semiconductor device itself.
BACKGROUND OF THE INVENTION
Lead frames comprise metal plates in which fine patterns such as inner leads and outer leads are processed. After mounting a semiconductor chip on the lead frame, terminals of the semiconductor chip and the inner leads are electrically connected to each other.
Recently, there has been an even stronger demand for a higher packing density and higher integration of semiconductor chips. Corresponding to such a demand, lead frames for mounting semiconductor chips thereon have also been developed which are of fine shapes and highly accurate dimensions. In particular, great weight has been given to increasing the number of pins per lead frame. With an increase in the number of pins per lead frame, a processing technique is required which can process distal end portions of inner leads to be smaller in pitch and finer in shape.
Conventional techniques for forming such lead frames having a number of pins and a narrow pitch from metal plates have been primarily practiced by a process utilizing chemical corrosion, particularly wet etching using an etchant (hereinafter referred to simply as etching). By that conventional processing method, lead frames having satisfactorily fine configurations can be easily processed.
Meanwhile, there is also known a method of processing metal plates, particularly lead frames, in combination of etching and laser cutting as disclosed in JP-A-3-123063 and JP-A-4-37493. The processing method disclosed in the former JP-A-3-123063 comprises cutting the portions having a narrow pitch, such as inner leads, by irradiation of a laser beam, and processing the portions not having such a narrow pitch, such as outer leads, by punching or etching. The processing method disclosed in the latter JP-A-4-37493 comprises etching a part of the total amount which is to be processed in the direction of plate thickness to form a recess having a curved inner surface. Then a post-cutting operation is undertaken the remaining part, which has been left not penetrated by the etching, by irradiation of a laser beam so that the remaining part is thoroughly penetrated to form inner leads having a narrow pitch.
The laser cutting employed in the above methods is suitable for fine processing because a laser beam can be condensed into a very small diameter, enabling metal plates, particularly narrow-pitch inner leads of lead frames, to be processed easily and reliably.
SUMMARY OF THE INVENTION
When processing fine portions of a metal plate from both sides by etching only, the metal plate is required to be etched half or more of the plate thickness from each side in order to penetrate the metal plate in the direction of plate thickness. However, since chemical corrosion such as etching is isotropic, the processed portion is also corroded in the direction of plate plane simultaneously by the same amount as in the direction of plate thickness (hereinafter referred to as side etching) and the finally formed gap has a width greater than the plate thickness. In other words, when metal plates are finely processed by etching, there exists a limit in that the processing and etching cannot penetrate the metal plate with a gap width less than the plate thickness. When metal plates are etched from one side, a portion corroded by side etching is further increased, making it more difficult to achieve fine processing.
On the other hand, with the methods disclosed in JP-A-3-123063 and JP-A-4-37493, by taking advantage of the feature of laser cutting, fine portions of lead frames having a narrow pitch for use in a high-density and high-integration semiconductor, for example, can be processed beyond the above-mentioned limit in process
REFERENCES:
patent: 4786358 (1988-11-01), Yamazaki et al.
patent: 5088008 (1992-02-01), Takeyama et al.
Miyanagi Naoki
Nagano Yoshinari
Sakurai Shigeyuki
Shimomura Yoshiaki
Tada Nobuhiko
Hitachi Construction Machinery Co. Ltd.
Powell William
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