Screen printing, carbon ink, silver glue, peelable adhesive and copper paste process (31-55)

31, On-Contact Printing sticky printing means that the printing plate is completely flat on the surface of the part to be printed, and then the printing method for pushing the ink with a squeegee, such as the Stencil printing method. This method can be printed after the full version of the shelf at the same time rise off the print surface, leaving solder paste on the circuit board. Unlike the Off-Contact Printing method, the tension of the stretching net is used. When the squeegee is pushed forward and pressed down, the net after the squeegee is also lifted up at the same time. Printed patterns can be kept clear, and common screen printing methods are the same. The schematic diagram of solder paste printing is to illustrate the difference between the two.

32. Plain Weave Weaving refers to a weaving method used in the screen printing, that is, when the warp and weft yarns are knitted in a One Over One Under manner, it is called a "flat weave method." For the screen printing method, the flat weave method has the best ink leakage. Nowadays, popular mesh fabrics are all made from monofilaments. When the number of meshes increases continuously to a certain limit, the wire diameter is so thin that the strength is insufficient and we cannot weave the mesh required for printing. . In general, when synthetic fibers (predominantly polyester-based "Tedoron") reach 300 mesh/inch (120 mesh/cm) or more, they cannot be used because of insufficient tension. Stainless steel can be re-dense to 415 heads/inch (or 165 mesh/cm) but still maintain sufficient tension. At present, the plain weave mesh used in the "screen printing" uses only monofilaments for easy cleaning and regeneration and convenient weaving. However, the multi-filament weaving method is still used for the weaving of fiberglass cloth in the sheet film (Pupreg) in order to improve the dimensional stability and facilitate the impregnation and penetration of the resin, as well as increase the contact area and adhesion.

33, Plug pins, plugs in the circuit board often refers to the connector or male plug part of the socket, can be inserted into the hole for the use of the interconnection can also be extracted at any time. The word Plugging is sometimes referred to as a "plug hole" and is a special resist that protects the wall of the hole so that the outer plate is positively etched, for the same purpose as the lid hole method. However, the plughole method can achieve the outer layerlessness to increase the density of wiring.

34, Pneumatic Stretcher pneumatic stretcher is a stretching tool for screen making, can be mesh from the four sides with its jaws to clamp it, and "pneumatic" mode carefully and slowly stretching uniform, Tension is set and changed. After it reaches the required data, it is fixed on the frame with glue, and it becomes the carrier of the circuit pattern and the squeegee. Because the tension can be controlled from the air pressure, it is more accurate than the "mechanical" tension, which helps the implementation of precision printing. The left picture shows the quick jaw and pneumatic cylinder of the "pneumatic tensioner". The picture on the right shows a lifting and tensioning net platform with multiple tensioners.

35. Poise is a unit of "viscosity" equal to 1 dyne. Sec/cm2, commonly used in centimeters Centipoise (referred to as Cp). The commonly used solder paste has a viscosity of 600,000 Cp to 1 million Cp.

36, pot life, pot life (processable time)
Refers to a two-liquid type of glue or coating (such as green paint). When the main agent and its special solvent or catalyst (or hardener) are mixed in a container, it becomes a workable material. However, once it is mixed, its chemical reaction is also started until it is nearing sclerosis and its useable time in the container is called Pot Life or Working Life.

37. Reclaiming regeneration refers to the process of screen printing between screen printing. When the original film (Stencil) on the fabric needs to be removed, and the new film is to be applied, the original film should be chemically used. It is softened and rinsed with warm water, or the mesh is further coarsened so that the new film can be fastened. These processes are called Reclaiming.

38. Again, this word also refers to the recycling of certain wastes. Relaxation is relaxation, relaxation is an abnormal phenomenon in the process of Zhang network. When the “net clamp” tightens the net cloth and suddenly tightens, the net cloth will feel loose and weak temporarily. After a period of reaction, the net cloth will gradually become tense. This is because of the phenomenon of "cold deformation" of the material itself and the process of redistribution of bit energy on the entire mesh. On-site operations should use the correct "net" step. Before the next tightening, it is necessary to relax a little, and then pull it to a greater tension to reduce the above "slack".

39, Resistor Paste resistance paste to the uniform particle size of carbon powder deployment paste, can be used as 20 ~ 50Ω/sq printed resistor (Resistor) purposes. This printing type "resistor" must meet the requirement of uniform thickness and neat edges, but the simple type resistor will gradually deteriorate after being used for some time in a warm and humid environment unless the use environment is particularly good.

40. The layout map of the Roadmap circuit and parts refers to the use of non-conductive paint, which is printed as a plan layout of circuit boards and parts to facilitate service and repair work.

41. Screen Printing screen printing is the use of a negative pattern of the net cloth, using a scraper to scrape the right amount of ink (ie, the resist), forming a positive pattern through the local net cloth, printed on the flat copper of the substrate. On the other hand, it constitutes a kind of masking agent and is prepared for subsequent selective etching or plating. This type of transfer is commonly referred to as "screen printing," and the mainland industry is called "screen printing." The screen materials used are: polyester, stainless steel, nylon, and silk that have been eliminated. Screen printing can also be used in other fields.

42, Screenability screen printing capacity refers to the screen printing construction, the ink in the scraping pressure action, through the exposed part of the net cloth, and the smooth leakage to the board or copper surface, and have a good ability to attach Words. When the obtained ink pattern also has a good resolution, the plate surface, the ink, or the machinery used can be said to have a good “printing ability”.

43, Silk Screen screen printing, silk screen printing with polyester mesh or stainless steel mesh cloth as a carrier, the positive and negative film pattern can be direct latex or indirect version of the film, transferred to the net frame on the cloth to form a screen As a tool for the printing of flat surfaces, it is called "screen printing". The continental term is abbreviated as "silkscreen."

44, Silver Migration silver migration refers to the silver paste jumper or silver paste through hole (STH) and other conductors, in a long time of high-humidity aging process, there is a DC bias between adjacent (Bias, refers to the two conductors When the potentials are not equal), there will be several mils of silver ion crystals extending each other, resulting in degradation of the isolation quality (Isolation) and even leakage, which is called "silver migration."

45. Silver Paste silver paste refers to a polymer paste prepared from 70% by weight of fine silver chips and 30% resin, and a small amount of high-boiling solvent as a thinning agent to facilitate the construction of screen printing. In addition to the jumper or through-hole conduction added on the board surface, silver paste can be used instead of the orthodox PTH. The latter is sometimes referred to as STH (Silver Through Hole). This method has the advantages of simple equipment, rapid construction, troublesome wastewater, and good conduction quality. Its resistance value is only 40mΩ/sq. The general STH costs less than two-thirds of the PTH, and is the darling of low-power, simple-function boards. It is often used in electronic equipment such as various remote controls or desk phones. Most of the global production of STH panels is concentrated in Southeast Asia and South Korea. Silver paste is mainly used by Japanese goods such as Fujikura and Hokuriku brands. In recent years, many board jumpers have been changed to carbon paste, and silver paste is used exclusively in the area of ​​through-hole double-panels. The "silver through hole" technology to achieve customer acceptance is not simple, often appear fracture, loose, and "migration" (Migration) and other issues. There are not many documents available for reference. The scene is only self-seeking and blessing. Experience is the main task to overcome difficulties.

46, Skip Printing, Skip Plating missed, leak plating in the dead side of the board printing process in some areas, due to poor ink distribution and the formation of missed printing, known as Skipping. This phenomenon is most likely to occur in Conformal Costing or green lacquer printing processes. Due to the corners on the back of the three-dimensional circuit, the green is often not sufficiently green due to uneven application of force or insufficient ink. Paint replenishment will result in "leakage". In the case of drain plating, electroplating may occur in a region where the bath fluid is strongly disturbed or in a low-current region, such as in the vicinity of the orifice and in the center of the pore wall of the pore, or due to the obstruction of bubbles, resulting in a poor distribution of the plating, and gradually causing Plating is difficult to grow. See also Step Plating.

47. The snapback height of Snap-off refers to the height of the net cloth from the board surface when performing screen printing; that is, the depth that the blade presses down to reach the board surface. Another way of saying this is the "air-height" Off-Contact Distance.

48, Squeege scraper refers to the screen printing tool to promote the ink walking on the screen. The main material of the squeegee is PU (Polyurethane Polyamines), which can be used to press the ink through the opening of the mesh and reach the surface of the printed plate to complete its graphics. Transfer.

49. Indirect screens, one of the important tools for screen printing on Stencil, have a pattern on the “ink surface” of the mesh. This kind of Stencil also uses a special photosensitive film, which can be transferred from the film first, exposed to light, and attached to the mesh after the image is developed. After the film is torn off by baking, it becomes a screen.

50. Tensiomenter Tensiometer When the mesh on the frame has been properly secured, use the "tension meter" to measure the tension of the mesh. The unit is generally Newtown/cm. The principle of this kind of measurement is to have two fixed support rods on both sides of the base, and a short, free-settling movable support rod in the center. This "activating short rod" is under the gravity of the counterweight. There will be a "falling" action pressing on the mesh to be measured, so that the "tension" supported by the partial mesh can be measured. The method of calibration is to first place the "tension meter" upright on a flat glass plate, and then adjust the zero reading of the surface reading from the lower hexagonal screw to measure the tension of the mesh cloth. (We are grateful to Mr. Yang Zhixiong, the director of the company. We hereby thank you.)

51, Thinner thinning agent that is used to dilute the "solvent", generally speaking, the thinning agent must not be chemically reacted with the diluted solute.

52、Thixotropy anti-sagging, shaking, thixotropic, static coagulation of certain colloidal substances, such as stirring, shaking, or shaking will appear liquefaction and flow phenomenon occurs, but when it is completely still, then it has become stale In the case of solidification, this characteristic is called Thixotropy. Common people such as ketchup or clay mud and so on. Printing inks used in the circuit board industry, especially green paints or solder pastes, must have this kind of "anti-sagging property" so that the printed three-dimensional "ink" or "cream blocks" will not collapse or flow. And other undesirable phenomena.

53. Ultra Violet Curing (UV Curing) Ultraviolet Hardening Ultraviolet light refers to light with a wavelength of 200 to 400 nm (nm means 10-9m; it can also be written as mμ, mili-micron), which is beyond human vision. outer. Light waves in this area have strong energy, and the photosensitive materials used for general plate making have the most sensitive wavelengths between 260 and 410 nm. The use of its specific energy to rapidly harden photosensitive glossy coatings without the need for baking and without the need for a diluent is very advantageous for automation. The circuit board industry can use UV-curing inks for circuit printing and has a wide range of applications for direct etching of single- or inner-layer boards.

54, Twill Weave diagonal weaving method, diamond weaving method is a kind of twill weave, a common plain weave method (Plain Weave), the warp and weft yarn in the cloth material is a combination of ups and downs. The oblique weaving method is one-two-up, two-two-two-jump and other weaving methods, and it looks like a twill cloth in a large area. The effect of such a net cloth on the surface printing has not been seen in various documents.

55, Viscosity Viscosity, viscosity The word in the circuit board process, simply refers to the ink in the flow (Flow) by the external thrust, the emergence of a resistance (Resistance), known as Viscosity. Generally thinner inks have lower viscosity, while thicker inks have higher viscosity. As for the true definition of viscosity,