Abstract: This paper introduces an antistatic cover plate, which is mainly used in PCB drilling process. The main resin of the cover plate is cardanol modified phenolic adhesive. Antistatic agent is added to the resin. Through physical mixing, the cardanol modified phenolic adhesive has certain antistatic performance, so that the cover plate can achieve antistatic performance. The performance of the cover plate is mainly verified by testing its resistance, hole position accuracy, broken needle rate, winding wire, etc.
Zero
Preface
With the development of 5g communication technology, it also affects the rapid development of related industries. The development of 5g technology puts forward higher requirements for the preparation of PCB. In the process of PCB preparation, there are many links. Each step needs to be strictly controlled to ensure the quality of PCB, so as to ensure the good performance of the final product. For example, in the process of PCB drilling, the accuracy of hole position, whether there is a sharp edge on the board surface and whether the roughness of the hole wall is qualified will affect the installation and use quality of the circuit board. The factors that affect the quality include the selection of the cover plate, and the improper selection of the cover plate will cause some problems in the drilling process.
This paper mainly introduces a preparation method of anti-static cover plate. Firstly, it ensures that the cover plate will not have fire, equipment abnormality, electric shock and other problems caused by static problems in the use process. Secondly, the anti-static main component used in this paper is surfactant products, which have certain cleaning and stabilizing effect on drilling needle and have a good impact on drilling quality 。
One
Experimental part
1.1 experimental raw materials, equipment and instruments
Experimental materials: cardanol modified phenolic resin adhesive, solid content 50%, Yantai Liuxin New Material Technology Co., Ltd.; antistatic agent, Shandong Juli Antistatic Technology Co., Ltd.; bleached wood pulp paper, imported from abroad.
Equipment and instruments: electronic balance, three port flask, electric mixer, electric constant temperature blast drying oven, four column hydraulic press, digital universal meter.
1.2 preparation of antistatic adhesive
Weigh 100g of cardanol modified phenolic resin adhesive in three flasks, then weigh 2.5G, 5g, 7.5G and 10g of antistatic agent respectively and slowly add them into the adhesive system, stir them for 2h at room temperature to prepare the antistatic cardanol modified phenolic resin adhesive.
1.3 preparation of antistatic cover plate
Bleached wood pulp paper is impregnated with antistatic adhesive to prepare impregnated paper. The impregnated paper is baked in an air drying oven at 150 ℃ for 60s to make a semi-cured sheet. The semi-cured sheet is cut into 15 cm × 20 cm in size. Then two semi-cured sheets are laminated in a press at 160 ℃, pressed for 30 min under 35 MPa, and the anti-static cover plate is obtained after the reaction. The samples of the cover plate are numbered No. 1, No. 2, No. 3 and No. 4 in order, and the corresponding amount of antistatic agent is 2.5G, 5g, 7.5G and 10g respectively.
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Two
performance testing
2.1 surface performance of cover plate
During the preparation of the adhesive, it was found that the color of the adhesive gradually deepened with the increase of the amount of antistatic agent added. Therefore, it can be judged whether the content of antistatic agent in the plate increases by judging the color change of the cover plate. The anti-static performance of the cover plate is mainly reflected by the surface resistance value, so this part mainly evaluates the surface color uniformity and surface resistance of the cover plate. Table 1 shows the various surface properties of the cover plate.
It can be seen from table 1 that with the increase of the amount of antistatic agent, the surface color of the cover plate is gradually deepened, and the surface color of the prepared cover plate is uniform, and the resistance values of all parts of the cover plate are not too different. From the surface resistance data of the cover plate, it can be seen that with the increase of the amount of antistatic agent added, the resistance of the plate surface gradually decreases, showing a good antistatic property. The decrease of the surface resistance of the cover plate also verifies the increase of the content of antistatic agent in the cover plate.
2.2 thickness test of cover plate
Thickness test can make us know whether the addition of antistatic agent will affect the thickness of the cover plate. The test results in Fig. 1 are obtained through the thickness tests of four different positions of cover plates. The thickness of four kinds of cover samples is about 0.44 mm, and the thickness difference glue of each position is small, which shows that the addition of antistatic agent does not affect the thickness uniformity of cover plate. At the same time, with the increase of the amount of antistatic agent, the thickness of the cover plate does not change much.
2.3 test and analysis of drilling performance
2.3.1 drilling conditions
The drilling test of the cover plate is mainly to simulate the drilling test of the soft plate on the experimental rig, so as to test the drilling performance of the anti-static cover plate. The drilling performance mainly shows the characteristics of hole position accuracy (CPK), needle winding, broken needle rate and surface plug. Table 2 shows the drilling test conditions.
2.3.2 wire wrapping of drill needle and hole shape
Under normal circumstances, the resin powder cut by the drilling needle during PCB drilling will be sucked away by the vacuum suction in the main shaft of the drilling machine, so as to maintain the cleanness of the drill bit and the hole. When the bit is drilling, the situation of wire wrapping will lead to the problem that the resin powder cut by the bit can not be completely discharged, the phenomenon of hole plugging and the inner wall of the hole is not smooth. Table 3 shows the basic patterns of drilling needle winding and cover plate orifice. All samples have no problem of drilling needle winding. From the point of view of the void state, there are different degrees of plumes at all sample orifices. Compared with other samples, the orifice state of sample 2 is much better. The experimental results show that the increase of the amount of antistatic agent can improve the overall antistatic performance of the cover plate, but it has no good inhibition effect on the orifice plume.
2.3.3 drilling accuracy analysis
The accuracy of drilling hole position is an important test to evaluate the performance of a cover plate. When the drill needle enters into the drill and contacts the cover plate, it will swing, and the drill needle will have small deformation. At this time, the drill needle will deviate from the original drilling position, resulting in a low accuracy of PCB hole position. When the hole position of PCB is low, the components on the PCB will be installed inaccurately or not because of the inaccuracy of the hole position, so the hole position accuracy is an important factor to evaluate whether the PCB can finally become a qualified board.
Figure 2 is the target map of hole position accuracy and hole position accuracy of cover plate. It can be seen from the figure that the better hole position accuracy is that the CPK value of sample 2 is significantly higher than that of the other three samples, and the CPK value of sample 4 is the lowest. Through the experimental data, it can be concluded that the increase of the amount of antistatic agent can improve the anti-static ability of the cover plate, but affect the hole position accuracy in PCB drilling of the cover plate, so the amount of antistatic agent is not the more the better.
2.3.4 comparison of needle breakage rate
The bit breakage not only affects the quality of PCB, but also increases the production time and reduces the production efficiency. Therefore, the bit breakage rate is also used as an important index to judge the PCB preparation field. In this experiment, 8009 holes were drilled in each cover plate, no broken needles were found in No. 1, No. 2 and No. 3 samples, and No. 4 samples were drilled 6590 times. Through the test of broken needle rate, it shows again that the increase of the amount of antistatic agent can not improve the drilling performance of the cover plate, and the addition of an appropriate amount of antistatic agent can not only improve the antistatic performance of the cover plate, but also make the cover plate have good anti broken needle performance.
Three
conclusion
This paper introduces the preparation and application test of an antistatic PCB drilling cover plate. By comparing the resistivity, cover plate thickness, surface morphology, drill needle winding, hole state, hole position accuracy and broken needle rate of the cover plate with different amount of antistatic agent, it is concluded that with the increase of the amount of antistatic agent, the antistatic performance of the cover plate is gradually enhanced, but the hole state and CPK of the cover plate are gradually enhanced However, it is not directly proportional to the anti-static performance, and the drilling performance with the best anti-static performance is the worst. Therefore, the amount of antistatic agent can not be too much, so as not to affect the drilling performance of the cover plate.
Author brief introduction
Dushan, Luo Xiaoyang, Liu Yubin: Yantai Liuxin New Material Technology Co., Ltd
END
*Published at home and abroad / monthly*
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Source: printed circuit information, February
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