1. Reduce the lateral erosion and along, improve etching coefficient

by:ShunDing     2020-05-26
Lateral erosion produced along. Usually printed circuit board in the etching liquid, the longer the more serious the lateral erosion. Lateral erosion seriously affect the precision of the printed wiring, severe lateral erosion will make the production of fine wire become impossible. When lateral erosion and tu along the lower, etching coefficient is higher, the etching coefficient of high said has the ability to keep thin wire, wire close to the original image dimensions after etching. Tin plating etch resist both - lead, tin, tin - nickel or nickel alloy, the excessive can cause wire short circuit. Because tu along is easy to break down in wire form electric bridge between two points. There are many factors which can affect the lateral erosion, overview the following points: 1) Etching method: soak and bubbling etching can cause larger lateral erosion, splash and spray type etching smaller lateral erosion, especially in the spray etching effect is best. 2) Etching liquid type: different etching liquid composition is different, the etching rate is different, have different etching coefficient. For example: acidic copper chloride etching liquid etching coefficient is usually 3, alkaline etching coefficient of copper chloride etching liquid can be up to 4. Recent studies show that on the basis of nitric acid etching system can be done almost no lateral erosion, achieve etching line side close to the vertical. This is yet to be developed in etching system. 3) Etching rate: etching rate slow will cause severe lateral erosion. Etching quality had a lot to do with the speeding up of the etching rate. Etching the faster the speed, the shorter the time duration of the boards in the etching liquid, the smaller the amount of lateral erosion, etching the pattern of clear and tidy. 4) Etching liquid PH: alkaline etching solution PH value is higher, lateral erosion. Mao shown in figure 10 - 3 in order to reduce the lateral erosion, general PH value should be controlled in 8. 5 below. 5) Etching liquid density: the alkaline etching liquid density is too low will increase lateral erosion, shown in figure 10 - 4, selects the high concentration of copper etching liquid is beneficial to reduce the lateral erosion. 6) Copper foil thickness: to achieve the minimum lateral erosion of thin wire etching, had better use ( Super) Thin copper foil. And the more fine line width, the thickness of the copper foil should be the thinner. Because, the copper foil etching the thinner in the shorter time, the less the amount of lateral erosion. 2. Improve the consistency of etching rate between board and board in continuous board etching, etching rate, the more consistent, more can obtain uniform etching of the board. To achieve this requirement, must ensure that the etching liquid in the whole process of etching always stay in the best state of etching. This requires choosing easy regeneration and compensation, easy to control the etching liquid etching rate. Choose can provide constant operating conditions and parameters of various solution can automatic control technology and equipment. By controlling the amount of dissolved copper, PH value, solution concentration, temperature, solution flow uniformity ( The motion of the spray system or nozzle and nozzle) , etc. 3. High across the board surface uniformity of etching rate board fluctuation two sides, and floor all parts of etching uniformity is made by the board surface is the uniformity of etching solution flow. Etching process, the top and bottom panel of the etching rate is often inconsistent. In general, the lower the etching rate is higher than on board face. Because the accumulation of panel has a solution, and weakened the etching reaction. Can adjust the up and down through the nozzle drenching pressure to solve the phenomenon of uneven surface etching up and down. Etching of the PCB is a common problem in the same time to clean all the plate etching is hard to do, the board edge is faster than board etching center. Use nozzle spray system and oscillation is an effective measure. Can further improve by making the plate center and edge of spray pressure, plate front and back-end intermittent etching method, reach the surface etching uniformity. 4. Improve the safe handling and etching thin copper foil and the ability of the laminate in laminate, such as etching laminated lining board easy to winding on the wheel roller and the resulting waste. So, etching lining board equipment must ensure that the smooth, reliable processing thin laminate. Many additional gear or roller equipment manufacturers on the etching machine to prevent the occurrence of this phenomenon. A better approach is to adopt additional swing teflon coating covered wire transfer as a laminate of supports. For thin copper foil ( For example, 1/2 or 1/4 ounce) The etching, must make the pledge that we shall not be scratches or damage. Thin copper foil are like 1 oz copper foil etching of mechanical defects, sometimes the severe vibration is likely to be cut copper foil. 5. Reduce copper pollution problem of water pollution is a universal problem in the production of printed circuit, the use of liquid ammonia alkali etching can worsen the problem. Because copper and ammonia complexation, not easy to use or alkali precipitation to remove ion exchange method. So, using the method of second spray operations, with no copper liquid was added to rinse the board and greatly reduce the discharge of copper. And then, with air knife before rinsing water to remove the redundant solution on board face, so as to reduce the burden of cu and etching salt water rinse.
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