Mehmet Murat Erdoğan - KİMYASAL İŞLEME NEDİR? (Tr/Eng)

Kimyasal İşleme:

Metallerin çoğunluğunun ve seramiklerin bazılarının bazı asit veya alkali çözeltiler içinde çözünme gösterdikleri yıllardan beri bilinmektedir.Metal atomları birer birer ayrılarak sıvı ile çevrelenmiş bölgenin tamamı çözülebilir.Endüstriyel uygulamalarda yüzeyin sadece bir kısmı dağlanır.Diğer kısımları balmumu,boya ve polimer film gibi maddelerle korunur.Daldırma veya püskürtme yoluyla tüm yüzeylerde kalın bir film oluşturulur, dağlanarak elde edilecek olan model bu yüzey üzerinde bir şablon boyunca bıçakla kesilir.

Kimyasal Enerji Kullanan Alışılmamış İmalat Yöntemleri:

Kimyasal enerji kullanan alışılmamış imalat yöntemlerinin ortak özelliği, kontrollu kimyasal aşınma ile hassas şekilde malzeme işlenebilmesidir. Genellikle, aşınması istenmeyen yüzeyler uygun bir koruyucu madde (maske) ile kaplanır. Açıkta kalan yüzeylere aşındırıcı kimyasal sıvı püskürtülür veya iş parçası bu sıvı içine daldırılır. İş malzemesinin sıvı ile temas süresi işleme miktarı ve/veya derinliğini belirler. İşleme hızı genellikle sıvı özelliklerine bağlı olmakla birlikte sıvı yoğunluğu tipik olarak 0.025 mm/dak doğrusal işleme hızları verecek şekilde ayarlanır. Bu grup imalat yöntemlerine giren başlıca 4 işleme yöntemi vardır:
• Kimyasal İşleme (Frezeleme) (ChM)
• Fotokimyasal İşleme (PCM)
• Kimyasal Parlatma (ELP)
• Isıl Kimyasal İşleme (TCM)

ENGLISH

Chemical Machining Overview:

What is chemical machining?

Photo Chemical Machining (PCM) is also known as Photo Etching , Photo Chemical Milling, Photofabrication, Chemmilling and Chemical Blanking. Chemical machining is primarily used in the production of thin and decorative parts. Chemical milling is considered a precision process and is most commonly used to machine sheets and foils.

Chemical machining is widely used in the electronics and aerospace industries. Common applications of photo chemical machining include integrated circuit lead frames, surface mount paste screens, optical attenuators, encoder disks, jewelry and meshes.

Most commonly a photo-tool is produced to the exact geometry to be machined using a laser photo-plotter. The photo-tool selectively exposes a photographic film according to the computer-aided design (CAD) data.

Photo-resists are UV light-sensitive polymers. Photo-resists are applied to the metal to be machined as a liquid by dip coating, flowing, roller-coating or electrophoresis. The coating of the metal sheet with photo-resist sensitizes it. When this sensitized metal is put into the double-sided photo-tool and is exposed to UV light on both sides, an image is etched into the photo-resist. The photo-resist tool is then developed in a liquid formulation to form a durable image on both sides of the metal.

Companies that perform chemical machining often specialize in chemical machining only since chemical machining is a very different process than traditional machining.

Photo Chemical Machining
The processes of using photo chemical machining, photo etching, and chem milling, are ideal for thin metal parts fabrication, fine line etching, and engineering of micro machined parts. Many of these thin metal parts are then precisely formed into complex shapes.

Small Part Machined

Advantages: The advantages of photo chemical machining and photo chemical etching are quite diverse in what it can do for metal parts manufacturing. Large format panels, tight tolerances, and low cost of tooling are but a few of the advantages with PCM for producing burr free intricate metal parts. Additionally the time from concept design engineering, to prototype, to manufacturing the parts, is substantially reduced. Fine lines and traces can be etched quickly and accurately using chemical milling techniques as opposed to CNC milling.

All types of products can take advantage of the PCM and photoetching manufacturing processes. Everything from interconnects, RF and EMI shielding and fencing on PCB boards, microwave components, small antennas, fractal mulitband antenna geometries, microstrip devices, heat sinks, specialty flex circuits, hybrid circuits, precision springs, fine mesh screens, shadow masks for CRT devices, encoder disks, encoder strips, step lids, thermal frames, IC and PCB lead frames, PCB stiffeners, miniature contacts, precision scales, and a whole array of miniature components and micro machining possibilities that simply can not be produced cost effectively using conventional CNC machining or milling processes.

Metals And Materials Used: Various types of metals and materials can be photo chemically machined and etched. Alloys such as: kovar, nickel, brass, bronze, beryllium, copper, stainless steel, spring steels, tin, aluminum, tungsten, zirconium molybdenum, titanium, gold, silver, and other exotic materials can all be machined or photo etched using the PCM process. Various substrates such as teflon, duroid, polyimide, ceramics, copper foils, stainless steels, polymers, plastics, composites, and omega foils can be used in the parts. Ideally, the parts that can take advantage of the PCM process are built with thin metal sheets that are .062 inches or less in thickness. Parts and/or printed circuits, can additionally be built up, or deposited upon, the various substrates and material thicknesses, with very high precision using the PCM method. This provides engineers, when dealing with stringent design requirements, the means of taking full advantage of the micro precision manufacturing processes when designing new products and technologies with high precision, complex shapes, and excellent surface quality. See below.

Process: The photo chemical machining principal involves the process of reproducing a precise photographic image on the surface of a metal sheet or other substance with a photoresist, and the etching away (or depositing upon) the unprotected areas by chemmachining or electrical means. This conversion of the exposed work material takes place by an electrochemical reaction. View the Photo Chemical Machining Process Advantages.

Metal machined parts can be specially treated with a dielectric coating (superior to powder coating) for providing high Hipot electrical insulation values while at the same time maximizing and producing superior heat dissipation values. This type of dielectric coating has broad spectrum applications including: transformers, windings, RFI & EMI shielding, and laminations used in small motors.

Photo-etched Diskdrive Components

The industries that can take advantage of the PCM process are equally as diverse as the products themselves. Where tight tolerances and extreme thermal integrity are desired, the use of photo chemical machining for the manufacturing of certain components and highly complex parts, has been a benefit to the military, aerospace, NASA, and a host of other high tech industries for parts that need to be designed to handle the rugged use and the extreme temperature variations of equipment going into outer space. Satellites, Space Borne antennas, space fed lens antennas, smart antennas, ground based adaptive antenna arrays, and RF microwave antenna systems are continually being updated and designed to handle new types of communications and satellite direct imaging technology. With the need to develop new lower cost connectivity technologies, between low earth satellites, ground sensors, and continuous Internet connectivity requirements for military, research, and commercial applications; have resulted in a new breed of antenna engineering designs. Having to stay in-step with these new designs, new manufacturing processes and special application methods are being developed as these technology improvements have pushed the window of engineering and design beyond the limits of what can be manufactured using standard machining practices and fabrication operations.

Miniaturization of existing printed circuits and the ability of these circuits to handle additional power requirements has created a whole world need for hybrid flexible circuits, miniature parts, and heatsink components of all shapes and sizes along with new methods for fabricating them. As the proximity of these miniature devices have merged closer on the printed circuit boards and operation at higher RF frequencies have increased for the components, there exists a need for tuned EMI shielding and RFI fencing in a wide variety of applications. This is where the PCM manufacturing process can really shine; especially when intricate, custom formed shields are required.

Stacked memory arrays are another area of development where assembled components must be robust to handle the demands involved with military applications and severe use environments. Places where a hard drive would fail in a severe service environment, a stacked memory array can last through the same harsh environments. The assembly of these stacked memory arrays can take advantage of using an interconnect or multiple interconnects that have been precisely machined through the PCM and photoetching process. The interconnects not only provide the means of a superior electrical connection, but the metals and alloys used in stacked memory array assemblies are also natural heat sinks for superior heat dissipation.

Other industries that have used the photo chemical machining, chemical milling, and photo etching process for precision metal parts fabrication have included: Medical, Dental, Microwave, Telecommunications, Antenna, Cellular, Satellite, Communications, Circuit Boards, Flex Circuits, Optical, Electronics, Semiconductor, RFID,
Laser, and other High Tech OEMs.

CHEMICAL MACHINING PROCESS

A process for chemically machining metals, particularly steels and steel alloys, to depths greater than 0.010 inches by using a chemical etching solution. The metal is coated with an etch-resist, exposed to an energy source to harden and bond a predetermined area of the resist to the metal and then developed to remove the unhardened and unbonded resist. The metal is then recoated with resist, again exposed to an energy source to harden and bond the second resist layer to the first resist layer at the aforesaid predetermined area and then developed to remove the unhardened and unbonded resist. The metal is then passed through a chemical etching solution to chemically machine those areas of the metal unprotected by the double layer of resist.

What is claimed is

1. A method of chemically machining a metal comprising the steps of cleaning the metal, coating the metal with a layer of resist, drying said resist layer, positioning a film having at least one clear and one opaque area on the surface of the resist-coated metal to be chemically machined, exposing the film-covered resist layer to an energy source to harden and increase the bond of a predetermined area of the resist coating to the metal, developing off the resist coating from that area of the metal which has not been exposed to said energy source, recoating the metal and at least one area of hardened and bonded resist remaining thereon with a second layer of resist, drying said second resist layer, repositioning said film on the surface of said second resist layer, exposing this film-covered second resist layer to an energy source to harden said second resist layer adhered to said first resist layer, developing off the second layer of resist coating from that area of the metal which has not been exposed to said energy source and thereby leaving at least one area of metal having a double layer of hardened and bonded resist thereon, then chemically machining said metal area not coated with resist using a chemical etching solution, the steps of coating with a resist are accomplished by dipping the metal endwise into a resist, and between the first dip coating step and the second dip coating step, the metal is inverted end for end so that the double coating of resist has an even distribution over the surface of the metal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the process for chemically machining metals. More particularly, the invention relates to the process for chemically machining hard-to-etch metals such as steels and steel alloys, to depths greater than 0.010 inch.

2. Description of the Prior Art

The Giangualano et al. U.S. Pat. No. 3,376,138, issued Apr. 2, 1968 teaches a method of chemically machining thin metal sheets such as 0.0014 -inch-thick copper for use as a printed circuit board. Such a process can also be used to etch micro parts from thin metal sheets where depth of etch, and hence, resist breakdown, is not a problem.

U. S. Pat. No. 3,257,251 issued June 21, 1966, to Lewis et al. sets forth a method of chemically machining a pattern on an embossing roll using a repeat coating and etching process to achieve a desired depth. In this repeat process it is necessary to recoat the entire pattern area with a coating of resist before the embossing roll can be etched a second time. In the improved method of chemically machining disclosed herein, it is unnecessary to repeat the resist coating step after each pass through the etching apparatus. It is only necessary in using this improved method, to pass the metal through the etching machine as many times as is required to attain the desired depth of etch.

The Young U.S. Pat. No. 3,386,901, which issued on June 4, 1968, discloses a method of etching metal plates such as steel, to make embossing dies. Although this patent relates to an electrolytic method of etching metal, it does disclose the conventional process and materials used, both of which are old in the art, to prepare the metal for the first etching step which electrolytically achieves an etching depth of approximately 0.005 inch. To achieve an etched depth of about 0.025 inch, it is necessary to follow a rather intricate process of recoating the raised pattern and its sidewalls with a protective coating before the second etching step which again achieves an etching depth of about 0.005 inch. These steps are repeated until the desired depth of etch is attained.

Using the chemical machining process disclosed herein, it is not necessary to repeat any coating step between the etching steps in order to achieve a desired depth of etch. The method of this disclosure has been used to etch embossing dies and plates to a depth of about 0.036 inch without the need to repeat the resist coating step after the metal has been initially prepared using this method. Using this method, a steel plate bench model has been etched to a depth of 0.250 inch without breakdown of the resist which necessitated any recoating steps, and all the while maintaining good definition of the original shape of the design figure. The process described herein can also be used to etch other metals as well as steel, which is one of the most difficult metals to etch because of its slow etch rate, whenever it is necessary to hold fine detail, good definition and close tolerances over a large area, such as would be the case for a large area, repeat pattern embossing plate. The fine detail, good definition and close tolerances are especially very important when embossing a repeat pattern in register with a certain design area of the pattern.

SUMMARY OF THE INVENTION

The main object of this invention is to present a method of chemcially machining metals, and particularly zinc, steels and steel alloys, to depths greater than 0.010 inch, while maintaining fine detail, good definition and close tolerances, without utilizing any etch resist recoating step between etching steps.

The invention is directed to a method of chemically machining metal embossing plates or dies and metal stencils. The method includes the steps of cleaning the surface of the metal, coating the cleaned metal surface with a layer of etch resist and then drying this resist layer. Next, a photographic film having a desired design pattern thereon is positioned on the resist layer and the resist layer is exposed through said film to an energy source to harden and bond certain areas of the resist to the metal plate. The photographic film is then removed from the metal plate and the resist coating which has not been exposed to the energy source is developed off said plate.

At this point in the process, the metal plate is recoated with a second layer of etch resist and allowed to dry. The same photographic film is again positioned on the plate and the second layer of resist is exposed to an energy source to harden and bond this second layer of resist to the first layer of resist. The photographic film is then removed and the second layer of the etch resist which has not been exposed to the energy source is developed off the metal plate.

After completion of the above-described steps, the metal plate has a double layer of hardened and bonded etch resist thereon in predetermined areas. This metal plate is then chemically machined by passing said plate through an apparatus containing a chemical etching solution as many times as is necessary to etch the metal to a desired depth. As can be seen from the preceding brief description of this chemical machining method, there is no need to repeat the resist coating or any other protective coating steps after the metal plate has been prepared by this method and is ready to be passed through the chemical etching apparatus.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross-sectional view of a metal plate having a first layer of etch resist deposited thereon by dip coating.

FIG. 2 is a cross-sectional view of a metal plate having a dried first layer of etch resist deposited thereon and having a photographic film negative positioned over said resist for exposure of said resist to a light source through said film.

FIG. 3 is a cross-sectional view of a metal plate having a hardened and bonded etch resist remaining thereon after the photographic film negative has been removed and the unexposed etch resist developed off.

FIG. 4 is a cross-sectional view of a metal plate having a hardened and bonded first layer of etch resist remaining thereon and having a second layer of etch resist deposited thereon by a second dip coating after the metal plate has been inverted.

FIG. 5 is a cross-sectional view of a metal plate having a hardened and bonded first layer of etch resist, having a dried second layer of etch resist deposited thereon and having the photographic film negative of FIG. 2 positioned over said second resist layer for exposing said second layer of resist to a light source through said film.

FIG. 6 is a cross-sectional view of a metal plate, having a hardened and bonded first layer of etch resist on said metal plate and having a hardened and bonded second layer of etch resist covering said first layer of etch resist after the photographic film negative has been removed and the unexposed second layer of etch resist developed off.

FIG. 7 is a cross-sectional view of a metal plate which has been chemically machined in those areas which are not covered by the double layer of hardened and bonded etch resist.

FIG. 8 is a cross-sectional view of a chemically machined metal plate after the double layer of hardened and bonded etch resist has been stripped off said metal plate.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The first step in the process of chemically machining a steel embossing plate or die is that of cleaning the surface of the steel. This is accomplished by first degreasing the surface to be chemically machined with a commercially available chemical degreasing fluid such as Oakite 33. This degreasing fluid is, in turn, washed off the surface of the steel with a spray of demineralized water. The surface to be chemically machined is then thoroughly scrubbed with a slurry of pumice powder and water after which it is rinsed with a spray of demineralized water. The entire steel plate is then immersed in a tank of heated phosphoric acid to lightly phosphatize its surface and prepare it for coating with a metal etch resist such as K.M.E.R., a commercially available metal etch resist. The plate is then removed from the tank of phosphoric acid, again rinsed with demineralized water while wiping the surface with an absorbent cotton such as Photex manufactured by the Kendall Company to remove the smut formed thereon by the chemical reaction of the phosphoric acid with the steel and then blown dry with filtered compressed air which thus completes the first step of cleaning the surface of the steel plate which is to be chemically machined.

The next step is that of dip coating the steel plate into a tank of metal etch resist such as K.M.E.R. referred to above. The resist comprises 50 parts of K.M.E.R. and 50 parts of a commercially available thinner. FIG. 1 shows a steel plate 10 after it has been dip coated into a tank of metal etch resist. The metal etch resist 12 is shown only on one surface, surface 14 of steel plate 10 in FIG. 1. The metal etch resist 12 would also cover surface 16 of steel plate 10 when using a dip coating process such as is used in this embodiment. However, all of the drawings, FIGS. 1 through 8 inclusive are used to illustrate the chemical machining of one surface of steel plate 10 to produce an embossing plate or die. An alternative application would be to describe the steps heretofore described and those hereafter to be described for both sides 14 and 16 of steel plate 10 so that both sides of the plate could be chemically machined. This application could be used to produce a stencil for a particular design pattern. It should be noted that relative thicknesses of the elements of the drawings have been exaggerated to clearly show the diffe