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01
Processing and molding technology of CPU radiators
2024-10-12
From some perspectives, the processing and molding technology of the radiator determines the final performance of the radiator, and is the most important manifestation of the technical strength of the manufacturer. The mainstream molding technologies for radiators are mostly of the following types:
Aluminum extrusion technology (Extruded)
Aluminum extrusion technology simply means that the aluminum ingot is heated to a high temperature of about 520 ~ 540 ℃, under high pressure so that the aluminum liquid flow through the extrusion die with grooves, to make the first embryo of the heat sink, and then the first embryo of the heat sink for cutting, cutting grooves and other treatments are made into our common heat sink. Aluminum extrusion technology is easier to achieve, and the relatively low cost of equipment, also makes it in the low-end market in previous years has been widely used. Generally commonly used aluminum extrusion material AA6063, which has a good thermal conductivity (about 160 ~ 180 W/m.K) and processability. However, due to the limitations of its own material, the thickness and length of the fins can not exceed the ratio of 1:18, so it is difficult to increase the heat dissipation area in a limited space, so the aluminum extrusion heatsink heat dissipation effect is relatively poor, it is difficult to cope with today's rising high-frequency CPU.
Aluminum die-casting technology
In addition to aluminum extrusion technology, another process often used to manufacture heatsinks for aluminum die casting, by melting aluminum ingots into liquid form, filled with metal models, using die casting machine directly die casting molding, made of heatsinks, using the pressure injection method can be made into a variety of three-dimensional shape of the fins, heatsinks can be made according to the needs of the complex shapes, and can also be made with the direction of the fan and the direction of the airflow with the effect of the flow of the heatsink, and can make a Thin and dense fins can be made to increase the heat dissipation area, which is widely used due to the simple process. Generally commonly used die-casting aluminum alloy for ADC12, due to good die-casting formability, suitable for making thin castings, but because of the poor thermal conductivity (about 96 W/m.K), and now more domestic AA1070 aluminum to do as a die-casting material, its thermal conductivity as high as 200 W/m.K or so, has a good heat dissipation effect.
However, AA1070 aluminum alloy die-casting radiator there are some of its own can not overcome the inherent shortcomings:
(1) Excessive surface flow pattern and oxidized slag during die-casting will reduce the heat transfer effect.
(2)The internal microcondensation hole is high when cooling, and the substantial heat transfer rate is reduced (K<200 W/m.K).
(3)The mold is easy to erosion, resulting in a shorter life.
(4) Poor molding, not suitable for thin castings.
(5) Soft material, easy to change shape.
With the CPU main frequency continues to improve, in order to achieve a better cooling effect, using die-casting process of aluminum heat sink volume continues to increase, to the installation of the heat sink has brought a lot of problems, and this process of making the effective cooling area of the heat sink is limited, in order to achieve a better heat dissipation effect is bound to increase the fan air volume, and increase the fan air volume and will produce more noise.
Heat sink processing and molding technology
Joining type process
In this type of heat sink, fins are first made from aluminum or copper plates, and then bonded to a heat sink base with grooves using Thermal Paste or solder. The characteristics of the bonded heat sink are that the fins are not limited to the original ratio, the heat dissipation effect is good, and it is possible to choose different materials for the fins. The advantage of this process is that the Pin-Fin ratio of the heat sink can be as high as 60 or more, which has a good heat dissipation effect, and the fins can be made of different materials.
The disadvantage is that the use of thermal paste and solder bonding between the fins and the base of the interface between the impedance problem will exist, thus affecting the heat dissipation, in order to improve these shortcomings, the heat sink field and the use of two new technologies.
The first is the insertion of teeth technology, it is the use of more than 60 tons of pressure, the aluminum combined in the copper base, and the two do not use any medium between the two, from the microscopic point of view of the two atoms in a certain degree of interconnectivity, thus completely avoiding the traditional combination of the two produce interface thermal resistance drawbacks, and greatly improve the product's heat transfer to the ability.
Second is the reflow soldering technology, the biggest problem of the traditional joint type heat sink is the interface impedance problem, and reflow soldering technology is the improvement of this problem. In fact, reflow soldering and traditional jointed heatsink process is almost the same, just use a special reflow soldering furnace, which can accurately set the temperature and time parameters of the soldering, soldering with lead-tin alloy, so that the soldering and the metal being soldered to get full contact, so as to avoid leakage of soldering empty soldering, to ensure that the connection between the fins and the base of the fins and the base of the connection as close as possible to minimize the interface thermal resistance, but also to control the soldering copper of each soldering point. Control of each weld copper melting time and melting temperature of each weld to ensure that all weld uniformity, but this special back to the weld furnace is very expensive, the motherboard manufacturers use more, while the heat sink manufacturers are rarely used. Generally speaking, the heat sinks that adopt this process are mostly used in high-end and more expensive.
Flexure Process
Flexure process first folds copper or aluminum sheet into one-piece fins by molding machine, then fixes the upper and lower base plates with piercing molds, and then welds them to the processed base with high-frequency metal fusion welding machine. Due to the process of continuous bonding, it is suitable for heat sinks with high thickness to length ratios, and because the fins are one-piece, it facilitates the continuity of heat conduction, and the thickness of the fins is only 0.1mm, which greatly reduces the material requirements. The fin thickness is only 0.1mm, which greatly reduces the material requirement and maximizes the heat transfer area within the allowable weight of the heatsink. In order to achieve mass production and overcome the interface impedance when joining materials, the production process adopts simultaneous feeding of upper and lower plates, automated and consistent process, and high-frequency welding is used for joining upper and lower plates, i.e., the materials are fused to prevent interface impedance from occurring, in order to build up high-strength and tightly spaced heatsinks. Due to the continuous process, mass production is possible, and heat transfer efficiency can be increased due to significant weight reduction and efficiency improvement.
Forging Process
The forging process is to heat the aluminum block to the buckling point after heating the aluminum block, using high pressure filled with molds and formed, its advantage is that the fins can reach a height of more than 50mm, the thickness of 1mm or less, can be in the same volume to get the maximum area of heat dissipation, and forging is easy to get a very good dimensional accuracy and surface finish. But forging, due to cooling plastic rheology will have neck shrinkage phenomenon, so that the heat sink is easy to have thick and thin, uneven height, which affects the efficiency of heat dissipation, due to the low plasticity of the metal, deformation is easy to produce cracks, deformation resistance, the need for large tonnage (500 tons or more) of forging machinery, but also because of the equipment and molds of the high cost of the cost of the product is extremely high. And because of the high cost of equipment and molds, the cost is too high unless mass production.
The world has the ability to manufacture a cold forging heat sink manufacturers are not many, the most famous is Japan's ALPHA, and Taiwan is Taisol, MALICO-Taiye Technology. The advantage of cold forging is that it can be manufactured in the heat dissipation area than the aluminum extrusion is also a large heatsink, and because of the aluminum extrusion manufacturing process is stretching, so the aluminum metal organization is to bear the horizontal direction of expansion, while the cold satin direction is vertically compressed, so for the heat, cold forging accounted for a greater advantage, the disadvantage of the cost is high, and there are not many manufacturers who can manufacture and produce the technology.