As a rising star in the lighting field, LED lighting fixtures have promising market prospects in the next five years and show strong growth momentum. According to the development trend of continuously decreasing prices and improving performance of LED lighting fixtures, the comprehensive cost of the entire life cycle of most LED lighting fixtures will be significantly lower than traditional lighting fixtures in the next 1-2 years, becoming the mainstream lighting source.
As the casing of LED lamps, aluminum alloy and ceramic materials are traditionally used. In the past two years, new materials thermally conductive plastics have emerged and are gradually accepted by the majority of manufacturers, becoming a high-profile casing material.
To sum up, thermally conductive plastics have the following major advantages:
1. Insulation, flame retardant and high safety.
2. Light weight, density is about two-thirds of aluminum.
3. Convenient processing and molding, good mass production.
4. No need for secondary processing, more green and environmentally friendly.
Faced with numerous thermally conductive plastic suppliers, how to more reasonably select cost-effective products, the following are some points worth paying attention to:
1. Considerations for narrowing the screening scope
1. RoHS and UL certification of thermally conductive plastics
Whether it has RoHS and UL certification will be a very critical factor for the whole lamp factory exporting to the European and North American markets. The issuing agencies of RoHS and UL certificates have actually done a preliminary screening of materials. For many manufacturers who are not familiar with new materials such as thermally conductive plastics, they can learn more about thermally conductive plastics through certification from testing agencies. It is worth noting that the UL certification number can be queried online, and its authenticity is relatively credible.
2. Material processing equipment required
The material properties of thermally conductive plastics are divided into thermoplastic and thermosetting. The vast majority of thermally conductive plastics are thermoplastic raw materials. Such materials can be produced by traditional ordinary injection molding machines. If the original manufacturer of energy-saving lamps owns a large number of injection molding machines, they can continue to use them. Another common practice is to outsource the injection molding process to professional injection molding companies. When the own production capacity is insufficient, you can easily expand production capacity through outsourced factories.
On the contrary, if the thermally conductive plastic is a thermosetting material similar to phenolic resin, an ordinary injection molding machine cannot be used, and a special thermosetting plastic injection molding machine must be used. The additional equipment costs will greatly increase the cost. And once the in-house injection molding capacity is insufficient, it will be more difficult to find a suitable outsourced injection molding factory.
From a practical perspective, the molding cycle of thermoplastic materials is shorter than that of thermoset materials, which also means that processing costs will be reduced.
3. Color of material
Usually, thermally conductive plastics are synthesized by adding additives to a certain base material (such as PC, PPS, PA). These thermally conductive additives are usually dark-colored materials, and the final customer demand is usually mainly white. If qualified white raw materials cannot be provided, it may result in an additional spray painting process after injection molding, thereby increasing costs.
4. Where the raw materials are produced
Based on the current export orders for LED lamps, delivery time will be an important term. If the thermally conductive plastic is produced domestically, the delivery time should be sufficient. If the origin is overseas, shipping and customs clearance import links usually have to be considered, and the delivery time will be extended. At the same time, the sales cost of imported raw materials will also be higher than that of the same domestic origin.
2. Comparison of material properties
1. Thermal conductivity
As a key technical indicator, the thermal conductivity of materials from various manufacturers currently attracts the most attention from users. The technical standards for testing thermal conductivity vary, including ASTM E 1530, ASTM E1461, standards defined by a certain company, etc. Even under the same technical standards, the testing methods are different, such as flat plate method and laser method. Under different testing methods, the error range of the final test results is completely different. Generally, the accuracy of the laser method is higher than that of the flat plate method, but the equipment involved in the laser method is basically imported and expensive.
It is precisely because of the above reasons that simply looking at the thermal conductivity coefficient will lead users to misunderstandings. A more realistic approach is to injection mold thermally conductive plastics from different manufacturers on the same mold, and then assemble the same lamp board and power supply. After powering on, test the pin temperature of the lamp bead or the temperature of the aluminum substrate close to the pin. The lower the temperature, the better the heat dissipation material.
Another approach is that thermally conductive plastic suppliers usually provide standard male mold products. You can compare the heat dissipation effect of the male mold with radiators of the same specifications and sizes (such as A19 bulbs) to roughly judge the performance of the material.
2. Material fluidity
is usually expressed by melt index. Thermal conductive materials with good fluidity are easier to mold and produce more smoothly. Based on highly fluid thermally conductive plastics, the wall thickness of the radiator can be designed to be relatively thin, usually 1-1.2mm. Thin wall thickness will shorten the heat dissipation path, thus improving the heat dissipation effect. At the same time, thinner wall thickness will reduce the weight of the material and reduce the material cost. If it is a material with poor fluidity, it is usually not easy to injection mold, and it will easily damage the mold and increase mold maintenance costs.
3. Molding Shrinkage
Usually when the thickness is 3mm, the qualified molding shrinkage should be below 0.5%. If it is greater than 0.8%, it will adversely affect the dimensional accuracy of the radiator. The molding shrinkage should be as small as possible. If you choose a material with a higher molding shrinkage, you will have to increase the wall thickness to compensate.
4. Mechanical properties
The mechanical strength of thermally conductive plastic radiators depends on several key indicators: Izod notch impact strength, tensile strength, and bending strength. The indicators of different materials can usually be compared. The larger the indicator value, the better. Thermal conductive plastics with excellent mechanical properties can add buckle designs to the radiator structure, so that the interface between the PC cover or lens and the radiator is realized through buckles, thereby avoiding complete reliance on adhesive for fixation. The problem with glue is that it requires curing time, which prolongs delivery time. At the same time, the glue easily atomizes at high temperatures, affecting the light output.
5. Flame retardant properties
There are two key points. First, whether it meets the UL94 V0 flame retardant level will be more critical for export to the US market. Second, whether it is halogen-free and flame retardant. Simply put, the flame retardant should not contain halogen, otherwise the environmental protection grade of the material will decrease and it will be difficult to pass the European RoHS and REACH directives.
6. Insulation properties
One benefit of thermally conductive plastic is insulation safety. If the injection-molded heat dissipation shell can withstand high voltages above 3500V, it should be easy to pass the safety test. Matching such an insulating shell, the available light board and power supply solutions can be more flexible, including: high-voltage linear lamp beads + high-voltage linear power supply, non-isolated power supply + medium-power lamp beads. Specific parameters can refer to dielectric strength.
7. Thermal expansion coefficient
If a plastic-coated aluminum structure is used in the radiator structure, the difference in expansion coefficient between the outer layer of thermally conductive plastic and the inner layer of aluminum alloy should be considered. The thermal expansion coefficient of aluminum alloy is: 0.000024 mm/mm*k. The expansion coefficient of the thermally conductive plastic should be at the same level. Otherwise, thermal expansion and contraction cannot be synchronized, causing the radiator shell to crack.
3. Price
As a category of plastics, thermally conductive plastics first follow the law of price based on quantity. At the same time, it should also be noted that the factors that affect the price are also closely related to the density of the material. Lower density materials actually reduce the unit cost. In addition, whether the material rod part in injection molding can be crushed and reused in injection molding actually has a certain impact on the price.
IV. Value-added services
As a supplier of thermal conductive materials, whether we can provide customers with thermal simulation testing services will provide a reference for judging whether the customer’s customized radiator is qualified for heat dissipation. This avoids the need to modify the mold if the heat dissipation is unreasonable after mold opening is completed, and thus avoids the risk of blind mold opening.
