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  Metal etching details

This video can help your friends to understand the entire process of etching and the key points of process control, which can help you fully understand the entire control process of metal etching. Metal etching a multi-process, multi-control one operation process, any process can determine the final quality. 

 

Metal etching is a technique that removes a material using a chemical reaction or a physical impact. Metal etching technology can be divided into two types: wet etching and dry etching. Metal etching consists of a series of complex chemical processes with different corrosion agents and different corrosion properties and strengths for different metal materials.

The type of metal is different, and the etching process is different, but the approximate process is as follows: the rough process is as follows: metal etching plate → cleaning and degreasing → water washing → drying → filming or screen printing ink → drying → exposure pattern → development → Washing and drying → etching → film removal → drying → inspection → finished packaging.

Generally, the metal etching is also referred to as photochemical etching, which means that the protective film of the metal etching region is removed by exposure plate making and development, and the chemical solution is contacted during metal etching to dissolve and corrode, thereby forming the effect of unevenness or hollowing. It can be used to manufacture printed embossed plates such as copper plates and zinc plates. It is also widely used in the processing of lightweight reduction instrument panels, thin-shaped workpieces that are difficult to process with nameplates and traditional processing methods. After continuous improvement and process equipment development, it can also be used. Used in the machining of precision metal etching products for electronic sheet parts in the aerospace, mechanical and chemical industries, especially in semiconductor processes, metal etching is an indispensable technology.

Metal etching process

The type of metal is different, and the etching process is different, but the rough process is as follows: metal etching plate→cleaning and degreasing→water washing→drying→filming or screen printing ink→drying→exposure pattern→development→water washing and drying→etching→ Film removal → drying → inspection → finished packaging.

1. Cleaning process before metal etching

 

The process before the etching of stainless steel or other metals is cleaned. The main function is to remove the dirt, dust and oil on the surface of the material. This process is a key process to ensure good adhesion of the film or screen printing ink to the metal surface, so it is necessary to thoroughly remove the oil stain and oxide film on the metal etching surface. Degreasing should be based on the oil stain of the workpiece. It is best to remove the oil before the screen printing ink to ensure the effect of degreasing. In addition to the oxide film, the best etching solution should be selected according to the type of metal and the thickness of the film to ensure that the surface is clean. It should be dried before screen printing. If there is moisture, it will also affect the adhesion of the ink, and affect the effect of subsequent pattern etching and even the appearance, affecting the etching effect.

金属蚀刻

 2. Stick dry film or silk screen ink photosensitive layer

According to the actual product material, the thickness and the precise width of the pattern are confirmed by dry film or wet film screen printing. For different thick and thin products, the time required for the etching of the product should be taken into consideration when painting the photosensitive layer. It is thicker or suitable for a thinner photosensitive layer, so that the hiding performance is good, and the texture of the metal etching process is high.

3. Drying

After the film or roll-on screen printing ink is completed, it is necessary to thoroughly dry the photosensitive layer to prepare the exposure process, and at the same time, it is necessary to ensure that the surface is clean, free from adhesions and impurities.

4. Exposure

The important process of metal etching, the amount of exposure energy will be determined according to the thickness of the material of the product, precision. This is also the embodiment of a company''''''''s technical capabilities. The exposure process determines whether the etching can ensure better dimensional control accuracy.

5. Development

After the surface of the metal etched plate is exposed to light, the patterned adhesive layer is exposed to light and solidified on the metal plate. Thereafter, unnecessary portions of the pattern, that is, portions to be etched away, are exposed. The development process also determines whether the final size of the product meets the requirements. This process completely removes the unwanted photoresist layer that is covered on the product.

6. Etching process

The most critical process is the etching of the chemical solution. This process determines the quality of the final product. It involves the concentration, temperature, pressure, speed and other parameters of the etching solution. The quality of the product needs to be determined by these parameters.

7. Unwinding

After etching, the surface is still covered with a layer of photoresist, and the photoresist on the surface of the processed product needs to be removed. Since the photosensitive layer is an acidic substance, most of them are subjected to bulking by an acid-base neutralization method, and after washing with water and ultrasonic cleaning, the photosensitive layer on the surface is removed. Mainly prevent the residual of the photoresist.

8. Check and package after the film is finished. The inspection of the size ensures that no defective products are discharged.

Reduce side etching and sharp edges, improve metal etching process coefficient

The side erosion creates a sharp edge. Generally, the longer the printed board is in the metal etchant, the more serious the side etch is (or using the old-fashioned left and right swing etchers). Side etching seriously affects the accuracy of printed conductors, and severe side etching will make it impossible to make fine wires. When the undercut and the edge are lowered, the etch coefficient is increased, and a high etch coefficient indicates the ability to maintain a thin wire, making the etched wire close to the original size. Electroplating etch resists, whether tin-lead alloys, tin, tin-nickel alloys or nickel, can cause shorts in the wires. Because the burs are easily broken, an electrical bridge is formed between the two points of the wire.

Improve the consistency of the etching process rate between the board and the board

In a continuous board etch, the more uniform the metal etch process rate, the more uniform the etched board can be obtained. To achieve this requirement, it must be ensured that the etchant remains in an optimal etched state throughout the etching process. This requires the selection of an etchant that is easily regenerated and compensated for easy control of the etch rate. Processes and equipment that provide constant operating conditions and automatic control of various solution parameters are selected. This is achieved by controlling the amount of dissolved copper, the pH, the concentration of the solution, the temperature, the uniformity of the solution flow rate (spray system or nozzle and the oscillation of the nozzle), and the like.

Improve the uniformity of the metal etching process rate on the entire surface of the board

The uniformity of etching on both the upper and lower sides and on the surface of the board is determined by the uniformity of the flow of the metal etchant on the surface of the board. During the etching process, the etching rates of the upper and lower plates are often inconsistent. Generally, the etch rate of the lower plate surface is higher than that of the upper plate surface. Because of the accumulation of solution on the upper plate surface, the progress of the etching reaction is weakened. The phenomenon of uneven etching of the upper and lower plates can be solved by adjusting the spray pressure of the upper and lower nozzles. A common problem with etched printed boards is that it is difficult to etch all of the boards at the same time, and the edges of the boards are etched faster than the center of the board. It is an effective measure to use a sprinkler system and to oscillate the nozzle. Further improvement can achieve uniform etching uniformity of the entire board surface by different spraying pressures at the center of the board and the edge of the board, intermittent metal etching etching at the front edge of the board and the rear end of the board.

金属蚀刻

Description of some common features of metal etching


About mold opening and cost: Relatively low mold opening costs, 200-1000 yuan in ordinary cases (special glass mask will be more expensive). The time to update the design is fast, and the design update can be completed in one day and the template can be completed at a lower cost.
New product development cycle: New product development for metal etching processes can be more flexible and less expensive. Designers can communicate with us in advance when developing new products, so that they can avoid some design flaws after discussion. For example: the material thickness of the design, the processing control precision of the design, the smallest hole that can be etched, the smallest gap, and the like. The design can be sent to the mailbox in advance: ly@sz-ydf.com for pre-discussion.
Metal etch processing can achieve some special effects: metal etching processing can achieve the bumping effect of stamping, cutting or CNC: such as some LOGO, brand logo, etc., and the stereoscopic effect is strong, the pattern is arbitrary, the fineness is high
Some metallurgical processing can control the accuracy: according to the material material, thickness, the processing accuracy of the factory can be converted into 10% of the thickness of the material, such as 0.1mm thick stainless steel, the control accuracy is +/-0.01mm
Metal etching can be processed in some shapes: almost any shape. Depending on the thickness of the material, the smallest opening that can be opened in the shape will vary. The thicker the board, the larger the gap that can be opened. Products with complex shapes can also be etched without additional cost.
Metal etching can process some material thicknesses: the most ideal state is: 0.05mm-0.5mm thickness interval. At present, the thickness of the material that can be processed in the factory is controlled at 0.02mm-2.0mm. The thicker the sheet, the longer the etching process will take and the higher the relative cost. At the same time, the processing cost of ultra-thin materials will not be low, and the process control and anti-deformation operations need special treatment.
Etching can process some materials: in theory, all metal materials can be etched or etched. Only different chemical materials are used for different materials, and materials with good corrosion resistance such as gold, silver, etc. even require aqua regia etching recipe to etch. Considering the risk factors and mass production, most of the factory is etched with SUS304, SUS316 stainless steel, and all copper, copper alloy, molybdenum sheet materials can be etched.
Special advantages of etching processing: etching is performed by means of chemical etching.
1. The most significant advantage is that the product is highly consistent with the raw materials. Does not change the properties of the material, does not change the material stress (except for the surface half-etching), does not change the hardness of the material, tensile strength and yield strength and ductility. The base processing process is etched in an atomized state in the apparatus, and the surface has no significant pressure.
2. No burrs: During the processing of the product, there is no pressure on the whole process, so there will be no curling, bumping or pressing points.
3. It can complete the separate molding action of the product with the stamping of the post-process, and can carry out the whole plate electroplating, adhesive, electrophoresis, blackening, etc. in a hanging point manner, and the relative cost is more saved.
4. Miniaturization, diversification can also be handled, and the cycle is short and the cost is small. This provides a better solution for some small or unicorn-type companies at home and abroad, using our dedicated sample set to achieve fast delivery, while ensuring product quality.

Metal etch processing connection point design

 
Metal etch processing thickness corresponding to the connection size design reference
Thickness(mm)
Recessed (notched)
Convex
depth
width
Projection height
Protruding width
0.10
0.15
0.60
0.05-0.15
0.12-0.15
0.15
0.2
0.75
0.05-0.15
0.12-0.15
0.20
0.25
0.90
0.05-0.15
0.12-0.15
0.25
0.3
0.90
0.20
0.12-0.15
0.30
0.35
1.00
0.20
0.2
0.40
0.4
1.30
0.20
0.3
0.50
0.4
1.50
0.30
0.4
0.60
0.4
1.60
0.36
0.4
0.70
0.4
1.65
0.30
0.5
0.80
0.45
2.40
0.40
0.5
1.00
0.45
2.50
0.40
0.5

 

 

 

 

 

 

 

 

 

 

 

 

Remarks: The units shown are all mm units.

Chemical etching solution formulation and process conditions

Different solution formulations and process conditions are required for etching different metals. The etching solution formulations and process conditions of commonly used metal materials are shown in Table 6-4 to Table 6-6.

Table 6-4 Formulation and process conditions of metal chemical etching solution 


Table 6-5 Metal copper chemical etching solution formula and process conditions

Table 6-6 Formulation and process conditions of chemical etching solution for zinc castings

Effect of process operating conditions

Etching is the key to the process of decorating the metal plate pattern. In order to obtain a pattern with clear stripes and strong decoration, it is necessary to control the etching conditions. Mainly the temperature and time of the etching solution. The high temperature of the solution can increase the speed of metal dissolution and shorten the time required for etching. However, the etching solution is generally a strong acid solution. When the temperature is high, the corrosion is strong, and the protective coating or the corrosion resistant ink is easily softened or even dissolved. The adhesion of the corrosion-resistant layer of the non-etched portion is lowered, and the corrosion-resistant coating at the interface between the etching and the non-etching is detached or melted, and the etching pattern is blurred and shaped, which affects the aesthetic and decorative effect of the pattern, so the temperature should not exceed 45 ° C. Similarly, if the etching time is too long, especially in the case where the temperature of the etching liquid is high, the etching time of the corrosion-resistant ink or the protective coating is too long, and the above-mentioned side effects and adverse effects are also caused, so the time control is also appropriate. Can not be immersed for too long, generally should not exceed 20 ~ 25min.

Discovery of FeCl3 metal etching principle

Fecl3 metal etching is one of the earliest processing methods used for copper and gold etching. This method is easy to obtain, cheap, simple to prepare, and easy to operate. Therefore, this method has been widely used even now. It has also been adopted by many copper etching plants. However, this method is more environmentally polluted and gradually replaced by other methods of corrosion.

 Fecl, corrosion of copper is a redox process in which Fe3+ copper is oxidized to Cucl3 on the copper surface while Fe3 is reduced to Fe3+

Introduction to the FeCl3 etching principle:

(1) Effect of FeCL3 concentration on etching rate: As the concentration of FeCL3 increases in the FeCL3 etching solution, the etching rate increases. When the FeCL3 contained exceeds a certain concentration, the etching rate decreases as the viscosity of the solution increases.

(2) Effect of the amount of hydrochloric acid added on the etching rate: Hydrochloric acid is added to the etching solution to inhibit the hydrolysis of FeCL3 and CuCL2, and the etching rate can be increased. Especially when the copper content in the etching solution reaches 37.4 g/L, the effect of hydrochloric acid is more remarkable.

(3) Effect of temperature on etching speed: In the FeCL3 etching process, the etching speed is also increased with the increase of temperature. For example, when the temperature is 50 degrees, the etching rate of copper by the new etching solution can reach 10um/min. However, in actual production, a normal temperature etching method is employed. The etching of copper by FeCL3 is an exothermic reaction. As the etching progresses, the temperature of the etching solution gradually increases and the etching speed increases. As FeCL3 is consumed, the etching rate decreases. At the same time, this temperature rise process is relatively slow, so the etching speed does not change much during the entire etching process.

(4) Effect of stirring on etching speed: The speed of static etching and the etching quality are relatively poor. This is because during the etching process, on the one hand, the copper surface and the etching solution are precipitated, which affects the normal etching of copper. On the other hand, during the etching process, the solution of the surface to be etched gradually appears dark green. This indicates that FeCL3 on the surface to be etched has undergone a reduction reaction with the copper surface and lost its oxidizing power.

            cu+FecI,一cucl十Fe~:1

Cucl ions have reducibility and further react with Fe ? of corrosive liquid leaf J to form cucl

           Cucl+FeCl、一Cucl2+FeCl 2

The resulting Cucl2 is oxidizing and also undergoes a redox reaction with copper.

           Cu+c∞12——2cucl    (5—43)

FeCl3 metal etching principle conclusion:

FeC:l, the metal etching solution is completed by means of Fecl, and cucl: simultaneously. Among them, n ? has strong oxidation ability, fast etching speed and good etching quality. In contrast, CucI2 has a high etching rate here, and the etching quality is poor. As the consumption of Fe3 in the etching solution and the increase of cuCL2, the etching rate is gradually slowed down, and the etching quality is deteriorated. When Fe3 consumption reaches 50%, the etching speed and etching quality will not be conducive to continue the etching process. Instead, replace the etchant.

In actual production, the etching efficiency of the metal etchant is not measured by the amount of Fe3 consumed, but by the amount of copper dissolved in the etchant (in gl/l). The initial etching rate of copper in the FeCl3 etching solution is constant. However, with the consumption of Fe 蚀刻 in the etching solution, the copper content in the etching solution is continuously increased. When the amount of dissolved copper reaches 60 g/L, the etching rate becomes slow, when the Fe3 consumption in the etching solution reaches 40% or copper is dissolved. When the amount reaches 83 g/L, the etching rate is drastically lowered, and the etching liquid at this time cannot be used any more, and the regeneration or renewal of the etching liquid should be considered.

 The commonly used FeCl 3 etching solution is not high in acidity, so the FecL3 etching solution is accompanied by the hydrolysis side reaction of FeCl and CuCI when etching copper:

    Fecl,+3H:O—Fe(OH)3 J+3HCI 

    cucl2+2H20一cu(on)2 +2HC:l 

The generated oxychloride is unstable, and it is easily decomposed by heat to form corresponding oxides and water. Some of these oxides precipitate at the bottom of the etching tank to form loess-like deposits, and some of them are suspended in the etching solution, which causes certain damage to the resist layer.

    2Fe(OH),一Fe202+3H3O 

    cu(OH)2—cuO +H2O  

Metal etching process characteristics

1. Target, the so-called goal is to have a clear output through the whole process of the process, to achieve a specific purpose. The purpose is to meet the product requirements of its design drawings. More specifically, these requirements include the etch size requirements of the product, the surface roughness requirements after etching, and the like.

2. Intrinsic, refers to a process must have its own specific content, which is included in each step of the process, as well as the behavior of all operators involved in these steps.

3. Integrity means that the process must consist of at least two or more processes. Because the process cannot be completed by a single processing step, at least two or more steps and their associated activities can establish a basic structure or relationship for circulation. For the metal etching process, it is also a complete process specification unit composed of multiple processes, process parameters of each process, tools specified by each process and related equipment, and is inseparable from each other. 

Metal etching exposure principle

First, the pattern to be etched is transferred to two identical films by lithography, and then the film is aligned by manual alignment or machine. Then, the steel sheet which has been coated with the photosensitive ink or the photosensitive dry film is placed in the middle of the film, and after exposure, it can be exposed. When the exposure, the steel sheet corresponding to the black portion of the film is not sensitized, and the steel sheet corresponding to the white portion of the film is photosensitive, and the ink or the dry film of the steel sheet is polymerized. Finally, after passing through the developing machine, the photosensitive ink or dry film on the steel sheet is not melted by the developing solution, and the unsensed ink or dry film is dissolved and removed in the developing solution, so that the pattern to be etched is transferred to the steel sheet by exposure.

The exposure is that under the irradiation of ultraviolet light, the photoinitiator absorbs light energy and decomposes into a radical, and the radical initiates polymerization and cross-linking reaction of the non-polymerized monomer, and forms a bulk macromolecular structure insoluble in a dilute alkali solution after the reaction. Exposure is generally carried out in an automatic surface exposure machine. The current exposure machine is divided into air-cooling and water-cooling depending on the cooling mode of the light source. Exposure imaging quality In addition to the performance of dry film photoresist, the choice of light source, control of exposure time (exposure amount), quality of photographic plate, etc. are all important factors affecting the quality of exposure imaging.

When the exposure is insufficient, due to the incomplete polymerization of the monomer, during the development process, the film melts and becomes soft, the lines are not clear, the color is dim, and even the degumming, the film is warped, etched, or even peeled off during the etching process; When it is excessive, it will cause difficulty in development, the film will become brittle, leaving residual glue and other defects. The exposure will produce a deviation in the line width of the image, and an excessive exposure will make the line of the picture thinner and the lines of the product thicker. Determine the appropriate exposure time based on the brightness of the dry film after development, whether the image is clear, whether the image line width matches the original film, etc.。 

The principle of roll coating protection oil before etching

The rubber roller and the steel wheel are pressed in parallel and rotate inward at a constant speed. The ink is sprayed from the hose to the steel wheel to uniformly adjust the tightness between the rubber roller and the steel roller, so as to control the thickness of the ink adhered to the rubber roller. And the uniformity; the steel sheet is pushed forward uniformly by the conveyor belt, and is properly contacted with the rubber roller, and the ink on the rubber roller is uniformly transferred onto the surface of the steel sheet. The coating technology is widely used in the etching of the anti-corrosion layer. The common coating methods include silk screen printing, dip coating, spray coating, and electrophoretic coating. The surface of the coated anti-corrosion layer should be uniform and complete, without blisters, white spots, etc. If the anti-corrosion layer is found to have the above-mentioned quality defects, and these defects are in the vicinity of the graphic lines, especially the fine graphic lines, the anti-corrosion should be removed. The layer is recoated. After the photosensitive ink sprayed on the workpiece is dried, a quality check is performed before exposure. The inspection items include no scratches on the surface of the ink, pores, and uniformity of the ink. If the requirement is not met, the ink on the entire surface should be re-rolled.

* The adhesion of the photoresist to the steel sheet is achieved by the flow of the photoresist film along the surface of the steel sheet.

* Heating reduces the viscosity of the photoresist and increases the flow. The pressure can squeeze the flow resistance into the surface of the steel sheet.

Metal etching is not available for processing narrow, deep grooves

This is because the bubbles generated by the metal chemical etching reaction are concentrated under the edge of the corrosion-resistant layer, and the bubbles trapped under the corrosion-resistant layer actually act to separate the metal surface from the corrosive agent. As a result, it causes a very irregular corrosion and forms a very irregular edge, which is a trouble for a deeper addition. Although some good-performing corrosion-resistant materials are soft and easy to discharge air bubbles, even if the mechanical agitation method is used, the air bubbles at the edge of the anti-corrosion layer are completely discharged, but when processed to a certain extent, After the depth, even the method of mold agitation is not sufficient to completely discharge the bubbles at the edge of the corrosion-resistant layer. The most effective way to do this is to use a relatively time-consuming manual method to smooth the corrosion protection layer on the edge of the pattern. Another possible reason is the effect of the surface tension of the corrosive liquid. This situation also causes corrosion in the case of narrow or small radius surfaces. For deep groove processing, the width is not less than 4 mm, for depth. Small grooves or round holes require a width or radius not less than 1.5 times the depth.

The harm of acid and alkali in etching process to workers and treatment

1. Hazard and treatment of hydrochloric acid to workers

High concentrations of hydrochloric acid have a stimulating effect on the nasal mucosa and conjunctiva, which may cause corneal opacity, hoarseness, suffocation, chest pain, rhinitis, cough, and sometimes blood in the sputum. Hydrochloric acid mist can cause severe pain in the eyelids. In the event of an accident, immediately move the injured person to fresh air to deliver oxygen, wash eyes and nose, and rinse with 2% soda. Concentrated hydrochloric acid splashed on the skin, should be washed immediately with plenty of water for 5-10min, and coated with soda on the surface of the burn. Severe cases should be sent to hospital immediately. The highest allowable concentration of hydrochloric acid in air is 5mg/m3

2, H3PO4 harm to the staff and treatment

H3PO4 vapor can cause atrophy of the nasal mucosa, which has a strong corrosive effect on the skin, can cause skin inflammation and muscle damage, and even cause systemic poisoning. The maximum allowable amount of H3PO4 in air is 1 mg/m3. If you accidentally touch the skin during work, you should immediately rinse it with plenty of water. After washing H3PO4, you can usually apply it to the affected area with red mercury or gentian violet solution. If it is serious, you should send it to hospital for treatment.

3, commonly used metal etching material stainless steel SUS304 SUS301 mechanical properties: For the etching process, SUS304 material properties are more suitable for etching processing, SUS301 performance is hard, etching will have burrs, hole walls are not smooth and other defects.

Choice of metal etching methods

The manner of metal etching depends on the contact form of the workpiece in solution, namely, spray etching and bubble intrusion etching. There are two principles for selecting the etching method.

1. Production: Spray etching has high efficiency, high speed and high precision. It is suitable for production with certain batches. It is easy to realize automatic control, but the equipment investment is large, and it is not suitable for etching of shaped workpieces and large workpieces. The intrusion-type etching equipment has a small investment, is easy to etch, and has a wide range of workpieces.

2. Shape and size of the workpiece: For large workpieces, it is difficult to carry out spray etching due to equipment limitation, and the bubble intrusion type is not affected by the size of the workpiece. The shape of the workpiece is complicated, and some parts will be sprayed out of place during the spraying, which will affect the normal progress of the etching. The intrusion type is to infuse the whole part of the workpiece in the etching liquid, as long as the dynamic between the solution and the workpiece is maintained. It can ensure that all parts of the workpiece of the opposite sex can be filled with the etching liquid and the continuous replacement of the new liquid and the old liquid can be performed, so that the etching can be performed normally.

For small planar or nearly planar workpieces, spray etch is superior to invasive etching, regardless of efficiency or precision, if conditions permit. Therefore, it is preferred to use a spray type for a workpiece having a large batch size, a moderately sized workpiece shape, and a simple shape; if the workpiece has a large outer shape, it is difficult to use an etching machine, and the shape of the workpiece is complicated, and the batch size is not large. The formula is appropriate.

Post-processing problems with metal etched workpieces

After the protective film of the etched workpiece is removed, the metallic color of the gloss is revealed, for example, the brass decorative piece, the nameplate, and the unetched convex portion are bright golden yellow. The recesses that are etched are matt or matt, and the layers are clear. After rinsing and passivation, the surface is covered with a protective lacquer, which is the finished product. There are also various color paints which are filled in the etched recesses to form a colored pattern and then covered with a protective lacquer. After the high-end crafts are stripped, they are often plated, alloyed or gold or silver, and then filled with paint or directly covered. There are also partial plating, for example, without removing the protective film, plating other colors on the etched portion, and then removing the protective film, which is a product of gold and silver. It looks exquisite, gorgeous and noble. The protective paint for the cover was previously used by self-drying paint. At the time, it was good-looking but not durable. Nowadays, dry-type paint, violet (UV)-cured paint or electrophoretic paint is used. Stainless steel parts are used in industrial products. Usually, the protective film is removed and cleaned. Of course, special requirements may also require surface coloring, passivation or coating.

Environmental problems during metal etching

The main factors affecting the metal etching process are acid, alkali and Fecl3, which must be properly disposed of and must not be discharged. For acid and alkali wastewater, it is generally treated by neutralization. There are alkaline wastewater and acid wastewater in the etching process. They can neutralize each other. Of course, it is impossible to balance acid and alkali. Value, lack of compensation, so that the PH value meets the discharge requirements, while also eliminating excess metal ions, after precipitation, clean water can be discharged. The pollution of Fecl3 waste liquid to the environment is mainly its image. Where it is stained, it is a piece of yellow rust, which is very ugly and damages the environment. The waste coating should be canned and recycled by a professional processing unit. For the treatment of wastewater containing ferric chloride, the most common treatment method is to put lime milk, which not only can neutralize the citric acid, but also precipitate the ferric and other metal ions in the wastewater, and in the wastewater. The impurities have a cohesive effect.

The role of degreasing before etching

The purpose of degreasing is to remove grease on the metal surface, as a work requiring metal etching, whether it is processing circuit boards or processing general mechanical parts or decorative parts, or processing high-demand parts such as aerospace components or ships. . Some of the workpieces to be processed are patterned, some are structured etching, and some are only chemically etched on one or both sides of the workpiece. The surfaces of these workpieces must first be effectively cleaned. An ideal clean surface must be a surface that removes grease, rust, and scale while washing away various marking symbols and other insoluble foreign materials. The purpose of this cleaning action is to ensure the uniformity of the adhesion of the corrosion-resistant layer to the metal surface and the uniform etching rate.

The role of water washing during etching process

Water washing is a step that takes a lot in the entire process of metal etching, and is washed after each treatment. The purpose of washing: 1. Wash off the alkaline or acidic liquid film attached to the surface of the workpiece taken out from the alkaline or acidic solution and replace it with a clean water film to become a clean surface; 2. Transfer the workpiece from a process In the next step, the solution from the previous step is not taken to the solution in the next step. Therefore, water washing is an important process in the process of metal etching.

Metal etching process control

The guarantee of metal etching quality mainly comes from the control of the etching process. The control of the metal etching process is divided into chemical parameter control and physical parameter control.

1. Chemical parameter control

Chemical parameter control is critical to maintaining a uniform etch rate of the etchant. Chemical parameter control primarily involves control of the solution concentration and proportional control between the components in the solution. For the control of these two aspects, the concentration control of the former is easy, and the consumption of components in the solution can be determined by an analytical method. The latter is more difficult to control because the content of the additive in the etching solution is lower, and it may be difficult to analyze the material, or it is difficult to separate from the main material in the etching solution.

The basis of chemical parameter control is derived from the analysis of the composition of the solution rather than the empirical estimation. Of course, for some small factories, it is not excluded that the operator can observe the intensity of the etching process, the state of the surface of the etched metal, and the change of the color of the solution. Adjust according to experience and meet a certain degree of controllability. This method has certain practicability for a single etchant, but for a workpiece with complex composition and high requirements for metal etch depth uniformity, this method has great limitations and is difficult to ensure mass production. need. From the perspective of ensuring the stability of product quality, the etching factory is required to use the analysis results as the basis for adjusting the etching solution.

The analysis cycle of the chemical etching solution is mainly affected by the following factors: 1 solution volume; 2 initial concentration of the solution; 3 unit volume of the load; 4 etching amount (generally in days). It is easy to understand the influencing factors of these aspects. When the solution volume is small, the initial concentration of the solution is low, and the load per unit volume is large, the change rate of the composition of the etching liquid is faster, and the analysis period is shorter, and vice versa. In general, if the volume of the etching solution is not large, the analysis should be performed once per shift in the case of mass production (the shift here is calculated in 8 hours for one production cycle).

2. Physical parameter control

The control of physical parameters is divided into other parameter control determined by general parameter control and etching mode. The general parameter control mainly controls the time and temperature during the etching process: other parameters determined by the etching mode control the control of the degree of stirring of the solution including the immersion etching and the control of the ejection pressure of the jet etching. Within the controllable range of chemical parameters, the control of physical parameters is very important to maintain constant etch rate and etch uniformity. The control of physical parameters is much easier and more intuitive than the control of chemical parameters. At the same time, some devices have automatic control devices for temperature, time and injection pressure, and only need to input these parameters in advance. 

Any metal etch must have two indicators that need to be controlled, namely depth and surface smoothness. Although changes in physical and chemical factors have an effect on the etching depth and surface smoothness, the effect on the depth of the etchant composition and concentration is mainly a physical factor. Under the premise of constant temperature and pressure, The factor that ensures the etch depth index is the etch time, which is also controlled by time in actual production. For the surface smoothness, although the temperature change will have a certain influence, it is mainly affected by the chemical composition of the etching liquid. The influence of the added substance on the surface smoothness in the chemical group is greater than that of the etching main agent. It is also more difficult to adjust at the same time, but it can be controlled by experiment to determine the empirical value of a unit area consumption.

Shenzhen Yaodafa Precision Technology Co., Ltd.

——Design and sales of metal accessories, metal finished products

——One Stop Solutions Provider Of Your Metal Precision Parts

 Mr. Liu:86-135 3425 7051 (with WeChat)   /  86-755-2991 8923

E-mail: ly@sz-ydf.com

Skype:13534257051 / QQ: 252292527/Ali Wangwang : xieliuliu

Company CHN website: www.sz-ydf.com

Shenzhen Address: Building B5, Fumin Industrial Park, Tangwei,Fuyong Town, Bao’an District, Shenzhen China

Dongguan address: 3rd Floor, Building C, Yinfeng Industrial Park, No. 1-3, Nonglin Road, No. 1-3,Humen Town, Dongguan China

 

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