Telecommunications RF Filter Silver Plated

Material: Aluminum 43400

Surface treatment: silver plating inside cavity, spraying outside cavity

Aluminum alloy has the advantages of low density, high mechanical strength, good shock absorption performance, excellent casting performance, easy electroplating, spraying, good thermal conductivity, corrosion resistance and oxidation resistance, and has always been the first choice for communication filter cavity die casting materials. . With the further improvement of the product's requirements for corrosion resistance and thermal conductivity, the filter material has been changed from ADC12, ALSI12 to European standard 43400 and widely used. At the initial stage of replacing the 43400 material, the following die-casting defects occurred during the die-casting production process.

â‘ There is a large amount of dense air and shrinkage at the position of the product wall thickness, the resonant rod boss and the end face of the product filling end connector.

â‘¡The cooling teeth (height 75-100 mm, small end 1.2mm, draft angle 1.2 degrees) and the cold partition formed by the solitary column in the cavity.

â‘¢There are a lot of mold sticking and drawing phenomenon in the product.

â‘£ The product is deformed when ejected, and the flatness is seriously out of tolerance.

⑤The product has defects of inclusion and delamination.

In view of the quality problems in the production after the replacement of materials, our company conducts research and improvement from the aspects of materials, molds, and die-casting processes.

1.Analyze the influence of each element of the material on the product's mechanical properties, thermal conductivity, anti-corrosion performance, cutting performance, and die-casting processability, and formulate an internal enterprise standard for 43400 aluminum alloy for die-casting of the filter cavity.

â‘  There are two functions of silicon in aluminum alloy. The first is to increase fluidity, but this is mainly for filling under very low pressure such as gravity casting. Tests and practices have shown that there is little difference in filling performance between aluminum alloy without silicon and alloy with silicon at a filling pressure exceeding 1 MPa. Now, the injection filling pressure in the production of die-casting has reached 30 MPa or more. The alloys with the worst fluidity, such as wrought aluminum alloys and wrought magnesium alloys, do not have the difficulty of insufficient filling. The second point is also the most important point of the role of silicon in aluminum alloys, and it is also the most easily overlooked point. The role of silicon is to reduce the phase change volume shrinkage of the "liquid-solid" phase. Especially for high-silicon aluminum alloys, when the silicon content reaches about 20%, such as B390 and ADC14 aluminum alloys, the phase transformation volume can remain unchanged. As aluminum alloy die-casting is a unidirectional high-pressure and high-strength filling casting, it does not have the effect of reverse feeding. It is for this reason that the die-casting industry deliberately formulates aluminum alloy grades with relatively low phase change shrinkage and high silicon content.

â‘¡ With the decrease of silicon content, under the same die-casting conditions, the shrinkage and porosity of the die-casting blanks are serious, and the pass rate is significantly reduced. The main reason is that the decrease in silicon content results in a larger volume shrinkage of aluminum alloys.

â‘¢The reason for the large area of pores and shrinkage holes after the processing of the product wall thickness position has been analyzed. Therefore, the heat conduction requirements of the filter cavity and the die-casting processability are followed on the silicon ratio, and the upper limit is 10.5-11%. In the subsequent improvement of the mold gating system and the design of the die casting process parameters, it is ensured that the alloy can be improved in the direction of feeding in time when the liquid phase is transformed into the solid phase, so as to increase the density of the product and reduce the shrinkage and porosity. form.

â‘£The decrease of silicon and copper content reduces the mechanical strength of the product and increases the tendency of thermal cracking. The elongation of the alloy increases and becomes softer. It is easy to deform or even crack when ejected. On the one hand, the mechanical strength is improved by the proportion of Mg and Mn content, and the cooling time, ejection speed and ejection force and the spraying of the release agent are adjusted when the die casting process parameters are set to solve the deformation and cracking of the product during ejection. defect.

⑤ With the effect of element Mn, manganese can prevent the recrystallization process of aluminum alloy, increase the recrystallization temperature and significantly refine the crystal grains. The refinement of recrystallization is mainly through the MnAl6 compound dispersing particles to hinder the growth of recrystallized grains. Too much MnAl6 can dissolve impurity iron to form (Fe, Mn) Al6 to reduce the harmful effects of iron. Therefore, the content of manganese should not be too high and should be controlled within the range of 0.30-0.40%.

â‘¥ If the Fe content is less than 0.7%, it is not easy to demold. When the iron content is too high, intermetallic compounds FeAl3, Fe2Al7 dendrites and hard spots are formed. When the iron content exceeds 1.2%, the fluidity of the alloy will be reduced. Therefore, the content of Fe is controlled at 0.75-0.85%.

⑦Adding a small amount of magnesium to the aluminum alloy can increase the strength and yield limit, improve the cutting type and corrosion resistance, and can refine the grain.

According to the influence of each element, combined with the characteristics and requirements of the filter cavity and the manufacturability of die-casting, the alloy standard of its own enterprise is formulated.

2. The optimization of the mold pouring system. The purpose of improving the gating system is for better exhaust, better pressure transmission, which is conducive to the feeding of the alloy, shortening the filling time and prolonging the solidification time of the inner gate. (Only list 1 set of molds briefly,)

â‘ Increase the cross-sectional area of the inner gate of the mold, and the thickness of the inner gate is increased from the original 3.6mm to 3.8mm.

②Change the incident angle of the inner gate from 35° to 25°, and the length of the inner gate from 2.5mm to 1.5mm.

â‘¢By adjusting the plane incident area and longitudinal incident angle of the runner, adjust the position of the overflow port and overflow volume at the end to ensure that several strands of aluminum liquid can arrive at the same time and be discharged sequentially.

3. Improvement of die casting process

â‘  The quality requirements of the air holes in the cavity of the filter cavity and the connector surface are very high, and the requirements for the control of the slag inclusion and gas content of the molten aluminum are very strict. In order to ensure the reduction of the slag inclusion and gas content of the molten aluminum, the ratio of the recycled material and the quality of the recycled material are strictly controlled during smelting, and the molten aluminum is refined with a dedicated rotary degassing refiner. The refining time was increased from 360 seconds to 480 seconds, and the quality control of molten aluminum was strengthened through the hydrogen meter and profile detection.

②In order to improve the cold insulation between the radiating teeth and the solitary column at the end, the temperature of the machine-side holding charge is adjusted from the original 660°C to 680°C. The molten aluminum begins to cool down from the time when the feeding spoon is scooped, adjust the waiting time for the soup machine to ensure that the soup spoon is moved to the pouring port after the mold clamping is completed, and the waiting time for the soup is adjusted to 1-2 seconds, and Reduce the injection delay from 1.5 seconds to 0.5 seconds. Our company uses a five-link soup feeder instead of a dosing furnace. The heat loss of the pressure chamber is 3.89-6.12°C per second on average. Under normal circumstances, it will drop by 12-18°C. If the pressure chamber is filled with a low degree of pouring, the temperature will drop faster after the injection. The higher the temperature of the alloy, the lower the viscosity, the better the fluidity, the smaller the injection resistance, the less the pressure loss, and the better the pressure transmission effect.

③The mold uses a combination of water cooling and oil cooling to control the temperature of the mold to stabilize within the range of 220-240°C. During die-casting and filling, the molten metal encounters the cold cavity of the mold and forms a dense layer on the molding surface of the mold. One of the main purposes of controlling the mold temperature of the mold is to increase the thickness of the dense layer and make the temperature of the mold consistent. Use oil cooling and oil point cooling for the heat sink teeth and resonance rod column, and use water cooling for the thick wall and cross flow path.

â‘£The resonant rod boss and hundreds of threaded holes in the filter cavity need to be processed, and there are heat dissipation teeth with a thickness of 1.2 and a depth of 75-100mm, and the cavity wall thickness distribution is uneven. At the same time, many molds need to be designed to eject the front mold. The front mold is thick, resulting in a pressure chamber full of only about 32%. A low full degree will cause the aluminum liquid to stick to the lower part of the pressure chamber, and the contact area with the pressure chamber is large while pressing The contact area between the molten aluminum and the air in the chamber is also large, and the heat exchange between the molten aluminum and the air and the pressure chamber is faster. The molten metal near the lower part is likely to solidify first to form a condensation skin, which is broken during the high-speed injection process of the punch. The main reason for the product is interlayer, so the slow speed and the first speed should be used when injecting. Our company has ordinary four-stage injection and real-time control die-casting machines. In actual application, the real-time control machine uses uniform acceleration in the slow stage. The slow control of the ordinary machine is based on the empirical formula of the fullness of the pressure chamber:

(V is the slow injection speed to increase the slow filling speed, D is the diameter of the punch, K is the fullness of the pressure chamber)

⑤Because a quick injection energy will consume a part of the nitrogen storage energy, the starting point of a quick injection is the filling of the molten metal to one-third of the runner. The fast injection stroke is based on the theoretical formula:

(S is the fast injection stroke, M is the quality of the product and the slag bag, ρ is the density of the aluminum alloy, and d is the punch diameter)

Calculate the fast injection stroke and adjust it to start high speed when the molten metal enters about 15% of the volume of the cavity. This not only ensures the full wall thickness filling of the molten metal, but also ensures that the resistance of the molten metal accumulated at the front end of the inner gate does not hinder the flow of the alloy. The pressurization position ensures that the pressurization of the inner gate can play a role before solidification. Due to the large change in the solidification volume of 43400 alloy, the pressurization signal position is earlier than the original, from the original injection zero position 50mm to 70-80mm. The boost trigger pressure is set to 60 bar. The fast injection speed is increased from 4.5m/s to 4.8m/s.

â‘¥The nitrogen pressure of the fast injection and pressurized accumulators is controlled at different pressures in winter and summer. Generally, the pressure in summer is 5bar less than that in winter. In summer, the nitrogen pressure of the fast injection and pressurized accumulators is set to 105+5bar and 95+5bar. The fast pressure and booster energy storage pressures are 135+_5bar and 125+5bar. The casting pressure is 95+5MPA. The injection pressure is set to 35+5MPA, and the qualified rate of the product shrinkage cavity is above 98%.

⑦As the Si content is reduced, the shrinkage rate of the alloy is large and the high temperature strength is reduced. The casting itself has a greater tightening force, so the mold temperature is higher than before, and the cooling time and ejection speed are adjusted. When the casting has not reached the maximum tightening force, the mold will be demolded, and the mold will be maintained every day during production. .

⑧Due to electroplating and spraying of filter cavity die-casting parts, the performance and spraying requirements of the release agent are very high. Our company uses high molecular polymer without silicone oil and waxy XY90A release agent, and the concentration of water Increase from 1:160 to 1:140. The increase in mold temperature can better form a layer of film on the surface of the mold cavity. Through the adjustment of various process parameters, the problems of mold sticking, deformation, and flatness are effectively solved.

4. Conclusion

In order to better meet the requirements of the thermal conductivity and anti-corrosion performance of the filter cavity, it is necessary to use 43400 aluminum alloy with low silicon and copper content. In the application of new materials, through the research and practical application of material components, The material ratio suitable for die casting of the filter cavity, and through the improvement of the smelting process, the optimization of the die casting sequence, the adjustment of the die casting process, successfully solved the various defects of the 43400 aluminum alloy during the die casting of the communication filter, and improved the product Pass rate.

Q1:What the surface treatment ?

A1: For the suface treatment,there are

1. Mechanical surface treatment: sandblasting, shot blasting, polishing, rolling, polishing, brushing, spraying, painting, oiling, etc.

2. Chemical surface treatment: blue and black, phosphating, pickling, electroless plating of various metals and alloys, TD treatment, QPQ treatment, chemical oxidation, etc.

3. Electrochemical surface treatment: anodic oxidation, electrochemical polishing, electroplating, etc.

4. Modern surface treatment: chemical vapor deposition CVD, physical vapor deposition PVD, ion implantation, ion plating, laser surface treatment, etc.

Q2: What the general anozied layer is thick?

A2:Different anodized has a different oxide layer

* Ordinary anodized 5-30μm

* Hard anodized 25-150μm

Q3:What type of material we can process?

A3:Stainless Steel :SS201,SS301, SS303, SS304, SS316, etc
Steel: 4140, 4340, Q235, Q345B, 20#, 45# etc

Brass:HPb63, HPb62, , HPb59, H59, H68, H80etc
Copper : C11000,C12000,C12000 C36000 etc
Aluminum : AL2024,AL6061, Al6063, AL7075, AL5052, etc
Titanium : TA1,TA2,TB1,TC4,TC18, TI GRADE2,GRADE5

CNC processing of plastic materials:

*ABS - (Natural / Black / flame retardant /)

*PC / polycarbonate - (transparent / Black)

*ABS + PC - (transparent / Black)

*PMMA / acrylic - (transparent / Black)

*PA / Nylon - (Natural / Black / 30% GF)

*PP / PP - (Natural / Black / 20% GF)

*POM / acetate / Delrin - (black / white)

*PPS / PPS

*PVC / PVC (white / gray)

*PTFE / PTFE

*PEEK / PEEK

*Epoxy tool board

Precision metal processing has absolute advantages in Guangdong, China. We have a perfect production and processing industry chain here, and the production cycle is 95% guaranteed. Our engineers will provide the most high-quality solutions to escort your project after understanding your needs in all aspects!

http://www.zhong-zhu.com/