Coating processes – With winding – balling – rolling – or coiling – Metal or glass base
Reexamination Certificate
1995-12-14
2001-10-30
Talbot, Brian K. (Department: 1762)
Coating processes
With winding, balling, rolling, or coiling
Metal or glass base
C427S074000, C427S157000, C427S327000, C427S289000
Reexamination Certificate
active
06309698
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a manufacturing process for a lead-frame forming material, more specifically to a manufacturing process for a lead-frame forming material, whereby the lead-frame having a uniform quality can be produced in large volume.
BACKGROUND OF THE INVENTION
A lead-frame is a metal frame forming an extension line lead terminal with a die pad which is used for fixing a semiconductor pellet used in a plastic mold IC and a ceramics package IC. There is used for the metal frame, a lead-frame forming metal plate made of alloy mainly containing copper or copper-nickel as a material. In recent years, an element of an active metal series such as titanium and chromium has been added to the material as well. In any event, it is desired that the material used have good mechanical strength, high electric conductivity, high softening temperature, a coefficient of thermal expansion matching the coefficient of thermal expansion of a semiconductor pellet and a package material, secured flatness of a lead, small bending anisotropy, good heat releasing performance, and a low cost. A pattern is formed on the lead-frame forming metal plate by a punching out or by etching with an etchant. Punching can be carried out at a low cost and a precise pattern can be formed by the etching method.
In recent years, development in semiconductor and integrated circuit manufacturing accompanied with an increased demand for electronic parts using lead-frames has resulted in an increased requirement for producing lead-frame having uniform quality in large volume.
In manufacturing lead-frame, there has been used in the past, an alloy plate mainly containing, for example, copper or an alloy plate mainly containing copper-nickel, and in order to remove rust preventives applied on the alloy plate, the alloy plate was subjected in regular succession to a degrease treatment and an acid cleaning treatment. Then, a liquid resist was coated on the plate surface by a wheeler coating method. For example, a light-sensitive layer of a dry type, such as a negative type was deposited and dried to provide a light-sensitive material layer. After the light-sensitive layer was exposed through a prescribed etching pattern, it was then subjected to a developing treatment and any exposed parts of the light-sensitive layer were removed. Then, the alloy plate was dipped in an etchant to form a prescribed etching pattern on the alloy plate surface.
In order to produce a conventional lead-frame having such a pattern formed thereon while having uniform quality in large volume, many sheets of the alloy plates described above were purchased and a lot of these alloy plates were subjected in succession to a degrease treatment to remove rust preventives on the alloy plates and then subjected to an acid cleaning treatment in a batch treatment. Then, a light-sensitive material was coated on the alloy plates thus obtained, followed by drying, to manufacture many sheets of the lead-frame forming metal plates in large volume.
However, in the conventional manufacturing process described above for the lead-frame forming material, whereby a lot of the metal plates were subjected, in succession, to a degrease treatment, then to an acid cleaning treatment in a batch treatment, followed by coating a light-sensitive material on the respective degrease-treated and acid cleaning-treated plates thus obtained, followed by drying, foreign matter tends to get in between the metal plate and the light-sensitive layer, which can cause breaking of wire in the lead-frame thus obtained after forming a pattern. Accordingly, it has been difficult to manufacture lead frames in large volume while maintaining uniform quality.
SUMMARY OF THE INVENTION
The present invention is to provide a manufacturing process for a lead-frame forming material, by which such difficulties in the manufacturing process for a conventional lead-frame forming material are removed and a lead-frame having a uniform quality can be produced in large volume.
In order to achieve the above object, the manufacturing process for a lead-frame forming material of the present invention comprises subjecting a metal web continuously to a degrease treatment, then to an acid cleaning treatment, and, then coating a light-sensitive material on the treated metal web thus obtained, followed by drying to form a light-sensitive layer, and cutting the coated lead-frame forming metal web thus obtained in fixed lengths along a longitudinal direction or winding it into a roll.
DETAILED DESCRIPTION OF THE INVENTION
The metal web is desirably an alloy, mainly containing copper or copper-nickel, or sheet metal made of an alloy prepared by further adding active metal elements such as titanium and chromium thereto or a strip.
Acid and alkali can be used as the degreasing agent for the degrease treatment. More specifically, aqueous solutions of sodium carbonate, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, sodium hydroxide, sodium metasilicate, sodium silicate, sodium hexametaphosphate, sodium secondary phosphate, sodium tripolyphosphate, and sodium pyrophosphate can be used. Treatment is carried out under treating conditions of a degreasing agent concentration of 0.01 to 50 %, a temperature of 20 to 90° C., and a treating time of 5 seconds to 5 minutes.
In addition to the treatment described above, the degrease treatment for the metal web under the above conditions may be carried out by an electrolytic degrease treatment in which an electrochemical process is combined. Roughening may be carried out prior to the degrease treatment. A conventional roughening process using a brush can be used.
Carrying out such a degrease treatment generates smut and accordingly, the residue generated has to be removed. This smut can be removed by using phosphoric acid, nitric acid, sulfuric acid, and chromic acid, or a mixture thereof.
In the present invention, a clean plane free of residue is required. It is necessary also to wash the plane with water after each of the processes so that no residual solution is present. Thereafter, a light-sensitive layer is coated onto the web. It is required that the coating process, be carried out continuously and evenly. The light-sensitive solution includes a negative type and a positive type. The negative type includes bichromates+polymer, an aromatic bisazide compound+cyclized rubber, an azide series polymer, a vinyl cinnamate series polymer, a photopolymerizable monomer, and an oligomer. An o-naphthoquinonediazide series is used as well for the positive type. Flexibility and adhesiveness are required of both of the negative type and the positive type.
Further, there can be carried out a potassium fluorinated zirconate treatment described in U.S. Pat. No. 2,946,638; a phosphomolybdate treatment described in U.S. Pat. No. 3,201,247; an alkyl titanate treatment described in British Patent 1,108,559; a polyacrylic acid treatment described in German Patent 1,091,433; a polyvinyl phosphonate treatment described in German Patent 1,134,093 and British Patent 1,230,447; a phosphonic acid treatment described in JP-B-44-6409 (the term “JP-B” as used herein means an examined Japanese patent publication); a phytic acid treatment described in U.S. Pat. No. 3,307,951; a treatment by the salt of a lipophilic organic high molecular compound and divalent metal described in JP-A-58-16893 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-58-18291; to provide a subbing layer of hydrophilic cellulose (for example, carboxymethyl cellulose) containing a water soluble metal salt, for example, lead acetate, as described in U.S. Pat. No. 3,860,426; to carry out a hydrophilicity treatment by subbing a water soluble polymer having sulfonic acid group, described in JP-A-59-101651; subbing of phosphates described in JP-A-62-019494, the water soluble epoxy compounds described in JP-A-62-033692, phosphoric acid-modified starch described in JP-A-62-097892, the diamine compounds described in 63-056498, inorganic or organ
Kakei Tsutomu
Uesugi Akio
Fuji Photo Film Co. , Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Talbot Brian K.
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