What's Aluminum Heat Sinks Extrusion Precautions?

Aluminum is widely used in heat sinks because of its light weight and beautiful appearance, good thermal conductivity, and easy processing into complex shapes. There are three main types of aluminum alloy heat sinks: flat and wide, comb or fishbone; products with symmetrical shapes are easier to produce, most radiator profiles are flat and wide, with large and asymmetrical appearance dimensions, and the depth-to-width ratio of the grooves between the radiators is large, which makes production difficult. At present, 6063 alloy is widely used because it not only has good thermal conductivity but also good mechanical processing performance. The quality of aluminum profile heat sinks depends on the following aspects:

Aluminum Extrusion Heat Sink for PCB PCBA

1. Quality requirements of ingots
The surface of the ingot should be smooth, without segregation tumors or sticky sand mud. The end face of the ingot should be flat, and it should not be cut into steps or the cutting slope should be too large (the cutting slope should be 3㎜ inside). Due to the large steps or cutting slopes, when the heat sink profile is extruded with a flat mold, if the guide is not designed, the ingot directly contacts the mold. Due to the uneven end face of the ingot, some places contact the mold first, resulting in stress concentration, It is easy to squeeze the die tooth shape, or cause different discharge, easy to block or poor extrusion molding.

2. Requirements for the die
Because the die of the radiator profile is a lot of slender teeth, it has to withstand a lot of extrusion pressure, and each tooth must have high strength and toughness. If the performance difference is large, those teeth with poor strength or toughness are easy to break. Therefore, the die usually uses high-strength H13 steel, or high-quality imported steel. The die should be vacuum heated and quenched, preferably with high-pressure pure nitrogen quenching, to ensure the uniform performance of all parts of the die after quenching. After quenching, three temperings should be performed to ensure that the die has sufficient toughness under the premise of hardness HRC of 48~52 to prevent the die from breaking teeth.

Automation Equipment for Aluminum Extrusion Heat Sink

3. Reduce extrusion pressure
To prevent the die from breaking teeth, the extrusion pressure should be minimized. The extrusion pressure is related to the length of the ingot, the size of the alloy deformation resistance, the state of the ingot, the degree of deformation and other factors. Therefore, the cast rod of the extruded heat dissipation aluminum profile should not be too long, about the normal cast rod length (0.6~0.85 times). Especially when testing the mold and extruding the first cast rod, in order to ensure the smooth production of qualified products, it is best to use a shorter cast rod, that is, a normal cast rod length (0.4~0.6) double cast rod for mold testing. For radiator profile sections with complex shapes, in addition to shortening the length of the casting, you can also consider using a pure aluminum short casting for the first time for extrusion, and then use a normal ingot for extrusion production.

4. Extrusion process
The key to the production of radiator profiles is the first mold test of the extrusion die. If conditions permit, you can first perform a simulation test on the computer to see if the working band of the mold design is reasonable, and then perform a mold test on the extruder. The first mold test is very important. When the main plunger moves forward, the operator should move forward slowly under low pressure below 8MPa. It is best for someone to use a flashlight to watch the mold outlet. Only when each radiator of the extrusion mold is evenly extruded from the die hole can the extrusion be gradually pressurized and accelerated. When continuing to extrusion after the mold trial is successful, attention should be paid to controlling the extrusion speed to achieve stable operation. When producing radiator profiles, attention should be paid to the heating temperature of the mold so that the mold temperature is similar to the ingot temperature. If the temperature difference is too large, the metal temperature will drop due to the slow extrusion speed, which may easily cause mold blockage or uneven flow rate.