GB2110165A - Thin metal precision apertured sheets - Google Patents

Abstract

A precision metal part, such as an optical slit plate, consists of a laminate of first and second different plated metal layers, e.g. nickel and copper. The first layer is accurately patterned using a photoresist masked etching process. The second layer is used simply as a support and is patterned with a slightly broader pattern than the first layer and is produced either by chemically selective etching of the second metal through a photoresist mask after the first metal has been chemically selectively etched, or by patternwise plating of the first metal with the second metal through a photoresist mask and then etching the first metal layer. An additional supporting layer, i.e. a third layer, formed of the same metal as the first layer is optionally included.

Description

SPECIFICATION Structure of precision metal parts This invention relates to structures of precision metal parts made by using metal foils. More particularly, this invention relates to structures of precision metal parts in which precision degree is improved in manufacturing precision parts having fine shapes by the use of metal foils of 20 to 500,L, by manufacturing a laminate of plated layers of different kinds of metals, while providing accuracy of necessary pattern only by one kind of metal and using the other kind of metal simply as a support or providing accuracy of necessary pattern only by one kind of metal layer and removing the portions of an intermediate and the other kind of metal corresponding to the pattern of said first kind of metal layer or a slightly broader portion than said portion.

To-day as one example of precision metal parts, there are manufactured optical slit plates (encoder having a thickness of 30 microns to 200 microns by using stainless steel plate.

Their manufacturing process (conventional process) can be illustrated by referring to schematic drawings of from Figures 1 to 10.

Figure 1 is a cross-sectional view of a stainless steel foil, provided with resist coat on both the sides thereof for producing conventional encoder.

Figure 2 is a cross-sectional view of a stainless steel foil provided with resist coat, sandwiched between two film sheets on which a necessary pattern has been depicted in advance and exposed to light and subjected to development.

Figure 3 is a cross-sectional view of the foil of Figure 2 from which the film sheets have been removed.

Figure 4 is a cross-sectional view of the foil formed by etching the foil of Figure 3.

Figure 5 is a cross-sectional view of the foil product obtained by removing resist-coat from the foil of Figure 4.

Figure 6 is a plan view of conventional rotary encoder and Figure 7 is a cross-sectional viewof the encoder of Figure 6.

Figure 8 shows the state of removing top and bottom films after exposure to light and development.

Figure 9 is a cross-sectional view of a foil together with attached top and bottom films where there is no deviation between the patterns of the two films and Figure 9 is a cross-sectional view of a foil having a hole bored by etching.

Figure 10 is a cross-sectional view of a foil together with top and bottom films where there is deviation between the two films and Figure 10 is a cross-sectional view of a foil having a hole formed by etching, which hole is narrower than that of Figure 10.

1) Firstly in Figure 1, membranes of photosensitive resin (resist coat) are formed on both the sides of a stainless plate wherein lisa stainless plate and 2 is a resist coat.

2) In order to put a pattern on as stainless foil (or plate) provided with resist coat, said stainless foil is sandwiched with two film sheets on which a necessary pattern has been depicted in advance and exposed to light and subjected to development as shown in Figure 2. In this case it is necessary to make the top and bottom patterns coincide with each other. 3 is film sheets having patterns and 3 and 4 show the state of light exposure (see Figure 2).

3) After removing film sheets, said stainless plate is put into an etching vessel to subject it to etching from both the sides at the same time. Fugure 3 is a cross-sectional view of the stainless plate from which the film has been removed and Figure 4 is a cross-sectional view of the stainless plate formed by etching the stainless plate of Figure 3. 2 is resist remaining after light exposure and development. 5 is an etched part.

4) The resist coat is detached from the stainless plate as shown in Figure 5 to obtain d product. A product thus obtained according to a conventional process is shown in a plan view in Figure 6 but pattern is shown only in part (omitted in other parts) and in a sectional view in Figure 7. In both the figures, 6 are thin linear slits penetrated so as to allow passage of light.

Figure 8 shows the state where top and bottom films are removed after light exposure and development indicated in Figure 2: However, a product manufactured through the above-mentioned steps has following drawbacks.

1] It is utterly impossible to put together two film sheets containing patterns of thin lines in the unit of from several ten microns to 100 microns completely, so that the patterns correspond completely to each other. According to my experiment deviations of from 10 microns even at minimum to more than 20 microns at maximum have been confirmed. These deviations become greater with increase of area of film.

2] Film sheets stretch or shrink depending upon heat, humidity, etc. Even when they are put together completely so as to correspond completely to each other deviation becomes greater with increase of times of use.

3] Precision of etching decreases proportionally with increase of thickness of metal. Etching fromboththe sides is a process used for making precision of etching as high as possible. When a hole is bored in a metal plate by etching from both the sides as shown in Figure 9, and if there is deviation of figures between top and bottom film sheets as shown in Figure 10, deviated etching is formed as shown in Figure 10.

The precision of penetration is determined by the width a of a hole shown in Figure 9. If etching proceeds perpendicularly, an ideal state shown in Figure 9 is formed. If there is deviation of figures between top and bottom film sheets, the width a becomes smaller as shown in Figure 10. Figure 10 shows ideal state where etching is assumed to proceed perpendicularly. Moreover, side etching amount becomes greater proportionally with increase of thickness and accuracy for keeping necessary thickness becomes extremely difficult.

4] When a precision metal part is to be made from a milled metal such as stainless steel plate by etching, milling directionai property is formed in the milled metal plate and etching state becomes different in longitudinal and transversal directions. In other words, etching of metal is the elimination of individual metal particles but in case of milled metal, metal particles take transversely piled state like piled bricks, resulting in forming of rugged etched surface.

This is also a drawback of a conventional process.

It is an object of the present invention to provide a structure of precision metal parts having extremely higher accuracy in which the drawbacks shown in the above-mentioned items 1) to 4) have been overcome in case of production of precision metal parts from metal foils according to a conventional process.

It is another object of the present invention to provided a method for producing a structure of precision metal parts having extremely higher accuracy such as those above-mentioned.

The objects of the present invention can be attained by the structure of precision metal parts of the present invention and the method of the present invention.

The structure of precision metal parts of the present invention consists of a laminate of two plated metal layers of a first metal and a second metal of a kind different from the first or a laminate of three plated layer of a first metal, a second metal of a kind different from the first and a third layer of the metal same with the first layer metal, in which the accuracy of etching and plating for obtaining necessary pattern in said metal parts is improved only by the first metal layer and the second and the third metal layers are used simply as a support in the production of said metal parts from metal foils.

A method for producing a structure of precision metal parts having extremely higher accuracy according to the present invention, comprises placing a laminate of two plated metal layers of a first metal and a second metal of a different kind or three plated metal layers of a first metal, a second metal and a third metal which is the same kind with the first layer metal between a top and a bottom film sheet on each of which different patterns are depicted in advance, subjecting said laminate and film sheets together to exposure to light and development, said top film containing a depiction of necessary precise pattern for said precision metal parts and said bottom film containing a depiction of pattern necessary to hold the strength of the laminate, arrangement being made in advance so as to leave unexposed photo-sensitive resin in the parts other than pattern parts after development, removing the film sheets or both the side subjecting the laminate to etching with a first etching solution capable of etching the first metal but incapable of etching the second metal and then to etching again with a second etching solution capable of etching the second metal but incapable of etching the first metal so as to improve the accuracy by the first metal while using the metal in other layers simply as a support.

A method for producing a structure of precision metal parts having extremely higher accuracy according to the present invention, also comprises placing a second metal foil provided on both the surface thereof with membranes of a photo-sensitive resin, between a top and a bottom film each containing respective depiction of different patterns and subjecting said foil to exposure to light and development, said top film containing a depiction of a precision pattern necessary to said precision metal part, said bottom film containing a depiction of a pattern necessary to keep the strength of laminated foils formed by applying plating of a first metal which is different from said second metal while arranging so as to leave unexposed photo-sensitive resin in the parts other than pattern parts, after develop ment treatment removing the top and the bottom film sheets, placing said foils in a plating bath for said first metal to apply said first metal plating onto the part of the second metal foil where photo-sensitive resin is not adhered, treating the laminate with an etching solution which etches the second metal so as to improve the accuracy by the first metal layer and to use the second layer metal and the third layer formed by the adhering first metal to the second layer by plating.

The structure of the present invention will be illustrated by picking up a case of rotary encoder as in Figures 6 to 8 directed to conventional rotary encoder. Namely, it will be illustrated in Figures 11 to 15.

Figure 11 is a plan view of a rotary encoder having a structure of the present invention.

Figure 12 is a cross-sectional view of said encoder in the stage of fabrication where a top film sheet on which a slit pattern is depicted and a bottom film sheet on which a pattern suitable as a support is depicted, are removed.

Figure 13 is a cross-sectional view of said encoder in the stage of fabrication where a nickel layer having no adhered resist coat is etched.

Figure 14 is a cross-sectional view of the plate obtained by etching the copper of the plate of Figure 13.

Figure 15 is a cross-sectional view of the plate obtained by removing the resist-coat.

Figure 16 is a cross-sectional view of the plate which shows one unit of pattern of a fixed encoder.

Figure 17 shows the back side of said plate and Figure 18 shows the front side of said plate.

Figure 19 is a cross-sectional view of the plate in which unnecessary parts of copper foil is covered with resist.

Figure 20 is a cross-sectional view of the plate obtained by nickel-plating the plate of Figure 19.

Figure 21 is a cross-sectional view of the plate obtained by removing resist of the plate of Figure 20.

Figure 22 is a cross-sectional view of the plate obtained by removing the copper in the plate of Figure 22.

Figure 23 is a plan view of slits of a rotary encoder as well as a cross-sectional view of the same, Figure 24 is a cross-sectional view of a slit of a rotary encoder in which deviation between a precision surface and a support surface become greater.

Figure 25 is a schematical cross-sectional view of a milled plate and a plated nickel foil in which a is the milled plate before etching a is the same after etching, b is a plated nickel foil before etching and b is the same after etching.

The structure of the present invention is divided into two i.e. a part A which requires accuracy and a part B which requires a suitable thickness in order to insert the product into other parts i.e. a part necessary as a support.

Further, patterns in film sheets were made different i.e. one of the film sheet contains a depiction of a pattern of the part which requires accuracy and the other of the film sheet contains a depiction of a pattern of the support part and made into a part having a structure the same with the one indicated in a prior application No. 427917 of 1980 relating to a solid metal mask plate which is a metal plate having image holes penetrated from both the side in which the thickness of metal is divided into three at optional proportion and as an intermediate layer, a different metal which cannot be etched by an etching solution which is to corrode the metal of both the sides.

The rotary encoder having a structure of the present invention is shown in a plan view of Figure 11 and in a cross-sectional elevation of Figure 15. In place of a stainless plate 1 of conventional encoder, a laminate of different metal e.g. a plated laminate consisting of a nickel layer 8 as a first metal layer a copper layer 7 as a second metal layer and another nickel layer 8 as a third metal layer, is used. As second metal layer an alloy of nickel and phosphorous is also useful.

In Figure 12, there is shown the state where a top film sheet having a depiction of slit pattern (X) necessary for an encoder and a bottom film sheet having a depiction of a suitable pattern Y (e.g. a suitable pattern) which occupies broader area than the area necessary for slit pattern, forming steps relative to the slits of the encoder, are removed.

In Figure 13, there is shown the state where nickel part having. no resist coat is etched and in Figure 14, there is shown the state where copper of the plate of Figure 13 is etched and in Figure 15, there is shown the state where resist of the plate of Figure 14 is dissolved out.

For a fixed encoder which is used together with a rotary encoder, accuracy can be improved by the same structure Figure 1.6 is a cross-sectional view of one unit of pattern thereof. Figure 18 shows the pattern of atop film and Figure 17 shows the pattern for holding a bottom film. An actual encoder is a flat plate on which pattern of above-mentioned unit is repeated ona plane.

A rotary encoder of Figures 11 to 15 is produced according to an etching process (referto Example 1) but the one shown in Figures 19 to 22 is produced according to a plating process. Figure 19 shows a cross-section of a plate obtained by inserting a copper foil provided with photosensitive resin membranes on both the sides thereof between two films having depiction of different patterns in advance, and subjecting to light-exposure and removing the films, where unnecessary part of copper foil is coated with resist. When nickel plating is applied to the foil of Figure 19, a plate shown in Figure 20 is obtained. Figure 21 is a cross-sectional view of the plate of Figure 20 from which resist is removed and Figure 22 is a cross-sectional view ofthe product of Figure 21 from which copper is removed by etching.

The metal parts of the above-mentioned structure have various advantages.

1) Since accuracy can be defined by one side of slits and opposite side thereof can be bored roughly in the present structure, deviation e.g. a in width formed at the time of etching does not give influence upon the precision surface even when it occurs. As shown in Figure 23, it is arranged to make the deviation a i.e. a width from the edge of support surface to the edge of accuracy surface in the range of 10 - 20 micron in case of the slits of encoders.

Even when a becomes 2a by etching no influence appears on the accuracy surface.

2) Since a precision metal part is not manufactured in the present invention by using two overlaid film sheets having the same pattern, there will be no occurrence of accident.

3) Since the thickness of a part which requires precision can be veried freely and accurately, it makes great stride of improvement.

4) Metal parts requiring accuracy have been made heretofore by using film sheets of small area due to deviation of film sheets, itis now possible to use film sheets of larger area and mass production is now possible.

5) Since foils are made by a plating process, there is formed no directional properties of metal. On this account accident due to etching does not occur in the leeast and metal parts of excellent precision can be obtained.

As shown in Figure 25 in case of milled metal plates such as stainless steel plate, crystals of metal particles show a state as if bricks are transversally piled but as shown in Figure 26 in case of plated plate such as nickel plated foil, crystals of metal particles show a state as if bricks are longitudinally piled. Side-etching effect is much less at the time of etching of plated foil compared with that of milled plates.

6) When a part requiring precision is made only by a plating process, since no accident occurs at the time of etching, accuracy can be much improved.

Moreover, it will be sufficient that only necessary parts are plated with nickel and-steps can be saved due to no etching process.

Structures of precision metal plates of the present invention are illustrated in specific examples which do not limit the scope of the invention.

Example 1 A laminated plate having a thickness of 40 nickel, 40 y copper and 20 11 nickel (100 CL in total) was made by plating with a common nickel sulfaminate bath and a copper sulfate bath. Both the surfaces of the plate were degreased and washed with water. After drying the plate was coated with resist (TPR supplied from Tokyo Oka) and dried. Then the films shown in Figure 11 a and 11 b were printed on both the surface of the plate. After removing the films, the plate was subjected to development, washing with water and then etching.As for nickel etching, an aqueous solution of 10% HNO3 and 20% hydrogen peroxide was used and after etching at 28"C for 3 minutes according a spray process, the plate was washed with water. Then copper was etched with a commercial alkaline etching solution. After washing with water and drying, the resist was removed by a definite removing solution to provide a product plate.Through the above-mentioned steps it is possible to obtain a product having accuracy and a shape shown in Figure 11 and provided with all the advantageous properties of the present invention. (A removing solution suitable to resist is commercially avaiiable but trichloroethylene is also useful.) Example 2 After preparation of a copper foil having a thickness of 40 by using a copper sulfate bath as in Example 1, the same resist as in Example 1 was coated on both the surfaces of the foil. After printing films which is opposite to those of Example 1 (i.e.

positive to negative of Figure 1) the foil was subjected to development, water washing and plating in a nickel plating bath to give the same thickness as that of Example 1. After removing the resist, copper was etched according to a process same as in Example 1 to provide a product. As a result, the same product as in Example 1 was obtained.

Claims (5)

1. A structure of precision metal parts consisting of a laminate of a first plated metal layer and a second plated layer of metal different from the first, or a laminate of a first plated metal layer, a second plated layer of a metal different from the first and a third plated layer of a metal same with the first, in which accuracy of etching and plating for obtaining necessary pattern of said metal parts is improved only by the first plated metal layer and the second and the third layers are simply used as support in the production of said metal parts made of metal foils.

2. A structure of Claim 1 in which said first plated metal is nickel and said second plated metal is copper.

3. A method for producing a structure of prec;- sion metal parts having very high accuracy which comprises placing a laminate of two plated layers of a first metal and a second metal which is different from the first one or three plated layers of a first metal. a second metal which is different from the first one and a third metal which is the same kind with the first one, between a top and a bottom film sheets on each of which different patterns are depicted in advance, subjecting said laminate and film sheets together to exposure to light and development, said top film containing a depiction of necessary precise pattern for said precision metal parts and said bottom film containing a depiction of pattern necessary to hoid the strength of the laminate, arrangement being made in advance so as to leave unexposed photo sensitive resin in the parts other than pattern parts after development, removing the film sheets on both the sides, subjecting the laminate to etching with a first etching solution capable of etching the first metal but incapable of etching the second metal and then to etching again with a second etching soluttion capable of etching the second metal but incapable of etching the first metal so as to improve the accuracy by the first metal while using the metals in other layers simply (

4. A method for producing a structure of precision metal parts having very high accuracy according to Claim 3 in which the first metal is nickel and the second metal is copper.

5. A method for producing a structure of precision metal parts having very high accuracy which comprises placing a second metal foil provided on both the surface thereof with membranes of lightsensitive resin between a top and a bottom film, each containing respective depiction of different patterns and subjecting said foil to light exposure and development, said top film containing a depiction of precision pattern necessarytosaid precision metal parts, said bottom film containing a depiction of pattern necessary to keep the strength of the laminated foils formed by applying plating of a first metal which is different from said second metal while arranging so as to leave unexposed photosensitive resin in the parts other than pattern parts after development, removing the top and the bottom films, placing said foil into a plating bath for said first metal to apply said first metal plating onto the parts of the second metal foil where no photo-sensitive resin is adhered, treating the laminate with an etching solution which etches the second metal so as to improve the accuracy by the first metal layer and to use the second metal and the third layer formed by the adhering first metal to the second layer by plating, simply as a support.