CN102746795A - Polishing solution for printed circuit microsections and preparation method thereof - Google Patents

Abstract

The invention discloses a polishing solution for metallographic sectioning of printed circuits and a preparation method thereof, belonging to the technical field of printed circuit board manufacturing. The invention provides a polishing solution specially used for polishing metallographic sections of printed circuit boards, which is suitable for observation and research of polishing copper, nickel and other coatings fixed by crystal glue. The polishing liquid is composed of alumina powder, gallic acid (3,4,5-trihydroxybenzoic acid) and an organic solvent. The polishing liquid has the characteristics of simple preparation process, low price, and long-term stable storage of the polishing liquid. Its polished metallographic section has a flat surface for easy observation.

Description

A kind of polishing solution for printed circuit metallographic section and preparation method thereof

technical field

The invention belongs to the technical field of printed circuit board manufacture, and in particular relates to the polishing technology in the manufacture of printed circuit metallographic slices. the

Background technique

The miniaturization and high-density development of printed circuit boards requires the miniaturization of holes for interlayer interconnection functions and the popularization of buried blind hole technology in application boards. The hole metallization process needs to go through electroless plating or black holes to form a conductive layer in the hole, and then electroplate to thicken it. However, the quality of the hole metallization is often affected by the composition of the electroplating solution, the parameters of the electroplating process, and the large ratio of the designed plate thickness to the aperture. Qualitative control, so it is necessary to observe the effect of hole metallization by means of metallographic section, and finally select the appropriate design and plating solution to ensure the high quality of hole metallization. the

The process of making metallographic slices should ensure that the surface of the epoxy resin crystal glue and the metal layer of the circuit board slice is smooth and flat without destroying the original effect of hole metallization, so as to achieve reliable observation of the quality of hole metallization. After being polished with sandpaper of different meshes, the metallographic section needs to go through a polishing process at the end, and the quality of the polishing effect will directly affect the efficiency of observation. The polishing process is to use polishing cloth and polishing media to smooth and modify the surface of the metallographic section. The quality of the particle system used in polishing has a great influence on the polishing effect. The particle system of the polishing medium with good polishing effect must meet the following requirements: (1) The particle size of the micropowder is uniform; (2) High purity; (3) Good dispersibility and adsorption; (4) The powder particles have certain crystal It has a lattice shape and forms sharp sharp angles when broken to improve polishing efficiency; (5) It has suitable hardness and density, and has good wettability and suspension with aqueous solution. Corundum-type alumina has high hardness, and its fine powder can effectively cut a small amount of the surface of the slice when it rotates with the polishing cloth. The surface of the slice has high flatness, which meets the basic requirements for polishing effect. the

Commonly used polishing media include polishing powder and polishing liquid. Polishing powder is most commonly used in the polishing process, mainly including silicon carbide polishing powder, rare earth polishing powder and alumina polishing powder. Unable to accurately control the dosage will lead to a large amount of waste, long storage time will easily cause particle agglomeration, and the uneven distribution of polishing powder particle size will cause many scratches on the metallographic section, which will affect the overall polishing effect. The polishing liquid belongs to the liquid phase polishing material, which is to disperse the polishing powder in the organic or inorganic solution to form a certain concentration of the polishing powder dispersion. Compared with polishing powder, polishing liquid has obvious advantages: due to the wrapping of the liquid continuous phase, the polishing powder particles do not directly contact each other, which reduces the agglomeration; the polishing liquid has low viscosity, uniform particle distribution, and effective control of usage. However, when the fine particle aggregates in the polishing liquid are separated into single particles or small aggregates composed of a small number of particles and evenly invade the organic solution, the particles are prone to wetting due to their large surface energy. Forming an organic film or having an electric double layer or forming a polymer adsorption layer will have a positive effect on the initial dispersion of the particles, but for the deep dispersion of the particles, the balance between the dispersion and agglomeration of the particles should be considered. The preparation of a stable and reliable polishing solution is essentially the process of deeply dispersing the polishing powder in the solution. Therefore, the surface adsorption of the particles must be weakened by chemical modification or chemical modification of the particles, and the repulsion between the particles can be enhanced. Agglomeration of small particles occurs. Nie Zuoren et al. (Chinese invention patent, patent application number 200610001059.8) prepared a rare earth polishing solution for chemical mechanical polishing by ultrasonic dispersion method, Zhang He et al. Liquid, Gao Lu et al. (Chinese invention patent, patent application number 201010170416.X) prepared alumina polishing liquid by high-speed shearing method. The instruments and equipment involved in these methods for preparing polishing solutions are relatively expensive, and the process flow is complicated, so they are not suitable for wide application in large-scale industrialized PCB production. Zhai Haijun et al. (Chinese invention patent, patent application number 201110244241.7) used ball milling, treatment, re-separation, and dispersion methods to prepare nano-diamond polishing fluid. The production process is complicated and time-consuming. The invention provides a simple method for preparing polishing liquid through ball milling and stirring and diluting. the

Contents of the invention

The invention provides a polishing solution specially used for polishing metallographic sections of printed circuit boards, which is suitable for observation and research of polishing copper, nickel and other coatings fixed by crystal glue. The polishing liquid is composed of alumina powder, gallic acid (3,4,5-trihydroxybenzoic acid) and an organic solvent. The polishing liquid has the characteristics of simple preparation process, low price, and long-term stable storage of the polishing liquid. Its polished metallographic section has a flat surface for easy observation. the

Detailed technical scheme of the present invention:

A metallographic section polishing solution for printed circuit, comprising alumina powder, gallic acid and organic solvent, the mass percent content of each component is: 0.5%~3% of alumina powder, 0.1%~1% of gallic acid, and the rest It is an organic solvent; the organic solvent is ethanol or ethylene glycol. the

A preparation method for a printed circuit metallographic section polishing solution, comprising the steps of:

Step 1: Prepare gallic acid organic solution. Dissolve gallic acid in ethanol or ethylene glycol organic solvent to prepare a solution with a concentration of 0.5% to 1%. the

Step 2: Ball milling. The alumina powder is mixed with the gallic acid organic solution prepared in step 1, and then subjected to ball milling treatment. the

Step 3: Dilution. Add gallic acid, ethanol or ethylene glycol organic solvent to the mixed system after the ball milling treatment in step 2 for dispersion and dilution, and prepare the final polishing solution; the quality of alumina powder, gallic acid and organic solvent in the polishing solution The percentage content is: 0.5%~3% of alumina powder, 0.1%~1% of gallic acid, and the rest is organic solvent; the organic solvent is ethanol or ethylene glycol. the

Gallic acid is an additive to stabilize the mixed system. When the mass percentage concentration in the polishing solution is 0.1%~1%, it can effectively improve the polishing effect and keep the alumina powder uniformly and stably dispersed in the organic solution. The organic solution of gallic acid in step 1 is used as the pre-dispersion liquid for the alumina ball milling treatment, and its function is to act as a lubricant for the ball milling fine alumina powder. The particle size of the alumina powder after ball milling is controlled at 100±5nm, which can effectively prevent the particle size of the alumina powder from being too large and agglomerating at the bottom of the organic solvent due to gravity. The alumina pre-dispersion liquid after ball milling is directly added with organic solvent and gallic acid to disperse and dilute. When diluting, mechanical stirring or magnetic stirring is used to speed up the dispersion speed of alumina powder in organic solvent. the

The beneficial effects of the present invention are:

The invention provides a polishing solution specially used for PCB metallographic slicing and a preparation method thereof. While the product quality reaches the existing standard, the production cost is reduced, the operation is simple and easy, and the polishing solution can be stable for a long time after it is prepared. Storage, no reunion, long-distance transport or storage. the

Description of drawings

Fig. 1 is a schematic flowchart of a method for preparing a polishing solution for metallographic sectioning of printed circuits provided by the present invention. the

Fig. 2 is a scanning electron microscope picture of alumina powder after ball milling. the

Figure 3 is a metallographic microscope picture of a metallographic section. the

Detailed ways

The present invention can be realized by the following examples:

Example 1:

Preparation of solvent system: Dissolve gallic acid in ethanol according to the required ratio to prepare a solution with a concentration of 0.5% to 1%. the

Take a small amount of prepared solvent as a lubricant, and ball mill the alumina powder for 12 hours. Dilute the ball-milled alumina suspension to the above-mentioned ratio with the prepared solvent, and stir evenly. the

Take a small amount of the prepared polishing solution and place it on a wet polishing cloth for polishing. After about ten minutes of treatment, the surface of the crystal glue can be smooth and smooth, and there is no obvious scratch under the optical microscope. the

The prepared polishing solution can be stored for a long time under sealed conditions. the

Example 2:

Preparation of the solution system: Dissolve gallic acid in ethylene glycol according to the required ratio to prepare a solution with a concentration of 0.1% to 0.5%. the

According to the steps of Example 1, a small amount of prepared solvent was used as a lubricant, and the alumina powder was ball milled for 12 hours. Dilute the ball-milled alumina suspension to the above-mentioned ratio with the prepared solvent, and stir evenly. the

Take a small amount of the prepared polishing solution and place it on a wet polishing cloth for polishing. After about ten minutes of treatment, the surface of the copper layer will be smooth and smooth, and there will be no obvious scratches under the optical microscope. the

Claims (4)

1. a printed electronic circuit microsection is used polishing fluid, comprises alumina powder jointed, gallic acid and organic solvent, and each constituent mass degree is: alumina powder jointed 0.5%～3%, gallic acid 0.1%～1%, and all the other are organic solvent; Said organic solvent is ethanol or terepthaloyl moietie.

2. a printed electronic circuit microsection comprises the steps: with the preparation method of polishing fluid

Step 1: preparation gallic acid organic solution; Gallic acid is dissolved in ethanol or the terepthaloyl moietie organic solvent, is mixed with the solution of 0.5% to 1% concentration;

Step 2: ball milling; With alumina powder jointed with carry out the ball milling thinning processing after the gallic acid organic solution that step 1 is prepared is mixed;

Step 3: dilution; Mixed system interpolation gallic acid, ethanol or terepthaloyl moietie organic solvent after step 2 ball milling thinning processing disperse dilution, are mixed with final polishing fluid; The mass percentage content of alumina powder jointed in the said polishing fluid, gallic acid and organic solvent is: alumina powder jointed 0.5%～3%, gallic acid 0.1%～1%, and all the other are organic solvent; Said organic solvent is ethanol or terepthaloyl moietie.

3. printed electronic circuit microsection according to claim 2 is characterized in that with the preparation method of polishing fluid the alumina powder jointed particle grain size after step 2 ball-milling processing is controlled at 100 ± 5nm.

4. printed electronic circuit microsection according to claim 2 is with the preparation method of polishing fluid; It is characterized in that; When the mixed system after the step 3 pair step 2 ball milling thinning processing dilutes, adopt mechanical stirring or magnetic agitation, to accelerate alumina powder jointed rate of dispersion at organic solvent.

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