Wet Process and PCB Surface Treatment (3)

27. Sand Blast

It uses strong air pressure to carry various small particles ejected at high speed and spray them on the surface of the object as a surface cleaning method. This method can be used for rust removal of metal, or to remove difficult-to-tangle dirt, etc., which is very convenient. The types of sand sprayed are gold steel sand, glass sand, walnut powder and so on. In the circuit board industry, pumice powder is mixed with water and sprayed on the copper surface of the board for cleaning.

28. Satin Finish

Refers to the surface of the object (especially the metal surface) after various treatments to achieve the effect of luster. However, after this treatment, it is not a mirror-like full-brightness state, but a semi-gloss state.

29. Scrubber

Usually refers to the equipment that produces the grinding action on the board surface, which can perform grinding, polishing, cleaning, etc. The brushes or grinding wheels used are of different materials, and can also be carried out in a fully automatic or semi-automatic way.

30. Sealing

After the aluminum metal is anodized in dilute sulfuric acid, the “cell layer” of crystalline alumina on its surface has cell openings, and each cell opening can absorb dyes and be dyed. After that, it must be immersed in hot water again, so that the alumina absorbs a crystal water to make the volume larger, so that the cell opening is squeezed smaller and the color is closed to make it more durable, which is called Sealing.

31. Sputtering

Cathodic sputtering means that in a high vacuum environment and under high voltage conditions, the metal surface atoms in the cathode will be forced to leave the body, and form plasma in the environment in the form of ions, and then run to the surface. On the object to be processed at the anode, and accumulate into a layer of film, evenly attached to the surface of the work, called cathode sputtering coating method, is a technology of metal surface treatment.

32. Stripper

Refers to the stripping solution for metal plating and organic film, or the stripper for enameled wire.

33. Surface Tension

It refers to the molecular-level inward attraction on the surface of the liquid, that is, part of the cohesive force. This surface tension (shrinkage) force at the interface between the liquid and the solid will tend to prevent the liquid from spreading. As far as the cleaning bath liquid for the pre-treatment of the circuit board wet process is concerned, the surface tension (shrinkage) force should be reduced first, so that the board surface and the hole wall can easily achieve the effect of wetting.

34. Surfactant Wetting Agent

Chemicals used to reduce surface tension are added to various bath solutions in the wetting process to assist the wetting of the walls of the through holes, so it is also called “Wetting Agent”.

35. Ultrasonic Cleaning

The energy of ultrasonic oscillation is applied in a certain cleaning solution to generate semi-vacuum bubbles (Cavitation), and the friction force and micro-stirring force of this foam are used to make the dead corners of the objects to be cleaned also generate mechanical cleaning effect at the same time.

36. Undercut Undercutting

The original meaning of the word means that in the early days of artificial logging, the axe was used from both sides of the root of the tree to gradually cut down the big tree by means of up and down oblique mouths, which is called undercut. It is used in the etching process in PCB. When the surface conductor is sprayed under the cover of the resist, the etching solution will attack vertically downward or upward in theory, but because the effect of the potion has no direction, it will also Lateral erosion to occur, causing the conductor line after etching to show indentation on both sides on the cross-section, which is called Undercut. But it should be noted that only under the cover of ink or dry film, the side etching caused by direct etching of the copper surface is the real Undercut. Generally, after the secondary copper and tin-lead are plated in the pattern process, when the resist is removed and then etched, secondary copper and tin-lead may grow outward from both sides. The loss of inward erosion can be calculated according to the line width of the negative, and the outward widening part of the coating cannot be included. In addition to this defect in the copper surface etching in the circuit board manufacturing process, there is also a similar side etching situation during the development of the dry film.

37. Water Break

When the oil on the board surface is cleaned, a uniform water film will be formed on the surface after immersion in water, which can maintain good adhesion with the board or copper surface (that is, the contact angle is small). Usually, it can maintain a complete water film for about 5~10 seconds when standing upright. The clean copper surface can be maintained for 10 to 30 seconds without breaking when the water film is placed flat. As for the unclean board, even if it is laid flat, it will soon “water break”, showing a “Dewetting” phenomenon that is discontinuous and aggregated. Because the adhesion between the unclean surface and the water body is not enough to counteract the cohesion of the water body itself. This simple method of checking the cleanliness of the board is called the Water Break method.

38. Wet Blasting

It is a physical cleaning method for metal surfaces, driven by high-pressure gas, forcing wet mud-like abrasives (Abrasive) to spray on the surface to be cleaned to remove dirt. The wet spray pumice powder technology that has been used in the circuit board manufacturing process belongs to this category.

39. Wet Process

The manufacturing process of circuit boards includes dry drilling, lamination, exposure and other operations; but there are also plated through holes, copper plating, and even imaging and stripping in image transfer that need to be immersed in an aqueous solution. It is a wet process, the original name is Wet Process.