Laminate Quality Problem Analysis

The quality problem of laminate is a comprehensive reflection of the quality problems of resin, gluing and pressing. Although pressing is the last key process in laminate manufacturing, the quality of the semi-finished products produced in the previous process will have a direct impact on the quality of the laminate. Therefore, the quality problems of laminates must be analyzed comprehensively in order to find the exact reasons and take effective measures to solve them in time to improve the quality of laminates.

(1) Surface pitting This phenomenon is often prone to occur in thin sheets, mainly adhesive tape, especially the surface material with a small amount of glue, a low content of soluble resin, and poor fluidity of the resin. The second is the uneven pressure during pressing. In some cases, the pressure is low due to the long preheating time. Therefore, when preparing thin sheets, special attention should be paid to the fact that the soluble resin content of the adhesive tape should not be too low, and good surface materials should be used. If there is only a thin plate task due to the limitation of product specifications, the backing paper should be thicker and should be replaced frequently, the preheating time should not be too long, and the pressure should be kept up. In addition, the temperature of the hot plate should not be too high when the glue is flowing.

(2) The phenomenon of uneven surface and corrugation often occurs in adhesive cardboard with large resin content and low solubility. Due to the low fluidity of the resin, the phenomenon of uneven glue amount during gluing is easily reflected on the surface of the laminate. Present uneven and stuttering phenomenon. Therefore, it is necessary to pay attention to the uniform amount of glue control when gluing. When preparing materials, pay attention to turning each material upside down to 180° to make up for the uneven amount of glue caused by gluing, so that the surface condition can be improved.

(3) Laminate cracking The cracking phenomenon mainly occurs in relatively thick paper and cloth boards. In severe cases, the laminates with a thickness of more than 5mm will crack. The epoxy phenolic glass cloth board is not easy to crack, which is because of the strong adhesion of the glue. The cracking of the laminate has a lot to do with the resin adhesion. When the aging material is sandwiched between the laminate, the laminate will crack. Therefore, the material selection of the adhesive tape should be carried out, and the aging material should be selected and cannot be mixed into the blank. . In addition, if the amount of adhesive tape is too small and uneven, and the pressure is too low or the pressure is too slow, it is easy to cause cracking.

(4) The color in the middle of the surface is dark, and the surrounding is white. This is mainly because the adhesive tape has large volatiles, and the surrounding volatiles are easy to escape during preheating, and the residual volatiles in the middle are large, so the surrounding is white and the middle color is dark. This can be judged to be caused by volatiles from the fact that the withstand voltage in the middle of the board is lower than the withstand voltage at the white edge of the board. Therefore, it is necessary to prevent the adhesive tape from absorbing moisture, especially if the soluble resin content of the adhesive tape is too large, the low molecular substances generated during hot pressing will increase accordingly, and this phenomenon will be more serious at this time. Tests have shown that low molecular weight has a greater impact than moisture. Practice has proved that the volatile matter of the adhesive tape is less than 4% and does not produce white edges. Controlling preheating below 6% can produce no white edges or very few white edges. More than 6% white edges are more big.

(5) Surface fracturing This is mainly because the resin is pressed too fast when flowing and the substrate is crushed. Therefore, the number of pressing times and the pressure of the adhesive tape should not be too high during the flow of glue. If the unit pressure of epoxy phenolic glass cloth board exceeds 7MPa (70kgf/cm²), the glass cloth will be crushed.

(6) The thickness deviation of the surface area glue reinforcement material itself is large, which causes uneven glue amount or the lack of glue machine, which causes excessive glue amount at a certain position of the adhesive tape, uneven fluidity, and uneven heat transfer of the hot plate during preheating. , The soluble resin content is large, and the pressure is too fast when the resin flows. Therefore, the thickness deviation of the substrate should not be too large, the glue amount of the adhesive tape should be uniform, and the content of soluble resin should be reduced. When preparing the material, pay attention to turning a part of the adhesive tape upside down to 180°, and the pressure should not be too fast during preheating. Be careful to remove the condensed water from the pipeline and the hot plate.

(7) Large thickness deviation of laminate The common thickness deviation is that the edge is thick and the middle is thin, which is mainly caused by the unevenness of the edge of the steel plate. Therefore, the steel plate should be kept carefully, and the corrugated edge should be repaired before use. The large deviation also has the phenomenon that one side is thin, which is mainly caused by the fact that one side of the tape is old and the other side is tender, or the temperature of the hot plate is high on one side and the temperature on the other side is low, and the tilt of the hot plate is caused. Therefore, when preparing materials, pay attention to turning a part of the adhesive tape upside down to 180°, and the inlet and outlet of the pipes are arranged in a staggered manner. When preheating, pay attention to drain the hot plate and the water accumulated in the pipes, so as to prevent the hot plate from being high temperature on one side and low temperature on the other side. Check hot plate tilt frequently and make repairs in a timely manner. The thickness deviation also has a thick edge and a thin edge in the middle, which is mainly caused by the depression and deformation in the middle of the hot plate that has been used for a long time. The hot plate should be serviced.

(8) Sheet slipping out During pressing, the tape slips out from the steel plate, especially when the epoxy phenolic glass cloth is pressed, which is generally called "running material". There are many reasons for the material to run, such as the amount of adhesive tape is too large and too tender, the amount of adhesive on both sides is uneven, the material preparation is uneven, the material is not loaded correctly, the pressure is too fast and too high when preheating the glue flow, and the force of the hot plate itself is uneven. The phenomenon of material running will occur, and material running will cause personal equipment accidents, which must be prevented. When preparing materials, the same batch of adhesive paper cloth is used, and the glue content and solubility are basically the same. In case of running out of material, the steam should be turned off to cool down, but sufficient pressure should be maintained, the slippage should be observed, and adjustments should be made after stabilization, and then gradually increase the temperature of the steam to continue to suppress.

(9) Sticking to the steel plate or surface oil splashes This is mainly caused by the improper amount of release agent, the amount of inner release agent such as zinc stearate, calcium, barium, oleic acid is small, or the outer release agent is wiped too much If it is small and uneven, it is easy to stick to the steel plate. If the amount is too large or the release agent is rubbed, it is easy to produce oil splashes. Therefore, it is necessary to strictly control the dosage of the internal mold release agent, and it is necessary to wipe the external mold release agent, such as floor wax, silicone rubber, etc., the concentration of the mold release agent should be adjusted properly, and it should be wiped evenly to form a thin layer. . In addition, the sticking steel plate is related to the surface quality of the steel plate. The surface finish is poor or the treatment is not enough, and it is easy to stick to the steel plate.

(10) The phenomenon of excessive warpage of laminates often occurs in cardboards with a thickness of 7~15mm. The reasons for warpage are very complicated, such as uneven amount of adhesive tape, heating and cooling speed during pressing, and discharge temperature. Too high, the matching scheme is unreasonable, etc., but it is mainly caused by internal stress. Therefore, internal stress should be minimized. For example, when heating and cooling, steam or cold water should be supplied slowly to prevent the laminate from being severely heated or cooled. There must be sufficient cooling time, which cannot be shortened arbitrarily. When the water pressure is insufficient, the time should be appropriately extended. The matching plan should pay attention to the uniform heating of the laminate, and try to adjust the adhesive tape as many times as possible when preparing the material, which is beneficial to reduce warpage.

(11) Unqualified withstand voltage The unqualified withstand voltage is mainly for thin plates. Because the withstand voltage standard of thin plates is higher than that of thick plates, after the heat treatment process is cancelled, the withstand voltage of thin plates often fails to meet the standard requirements. The breakdown voltage of the sheet has a great relationship with the volatiles of the adhesive tape. Practice has proved that when the volatiles of 3020 tape are below 4%, the withstand voltage is qualified, the volatiles are unstable at 4.5%~5%, and the pass rate above 5% is extremely high. Low. Laminates with unqualified withstand voltage are treated with heat-baking treatment, which is generally effective, but some laminates with low withstand voltage are also unqualified by heat-baking. Hot-drying requires a lot of labor, so the adhesive tape should be stored in a dry warehouse without getting wet.