With the first edition of the LED lighting products and related components safety standard "ANSI/UL 8750" came into effect at the end of 2009, and obtained the American National Standard Institute (ANSI) and the Canadian Standard Association (CSA) Accreditation, after becoming the universal standard in North America, has accelerated this change. Although LED has the advantage of energy saving, it also has a well-known heat dissipation problem. Compared with traditional lamps, the LED power is low, and the input power is converted into heat energy. In addition, in order to obtain high power, multiple parallel use is often required. The substrate must provide sufficient heat dissipation. The heat-dissipating substrate, which is the key to LED performance, has a great influence on the safety of LED lamps. How to make the consideration of the delay to balance the safety of products and heat dissipation is a serious challenge for the industry. Through deconstruction of relevant standards, this paper points out the safety issues that must be paid attention to in the heat dissipation substrate, so that LED manufacturers have a deeper understanding of the safety design and cost considerations of the heat dissipation substrate, and prepare in advance. The key to heat dissipation lies in LED chip package and substrate design. LED lamps have strict requirements for heat dissipation, and must take into account the limited heat dissipation area and insulation between circuits. The substrate design is particularly important. Although the ceramic substrate can meet the requirements of heat dissipation and insulation at the same time, the ceramic substrate is very difficult to manufacture, and its brittleness is not conducive to large-area arrays. The manufacturer has to use the insulating material on the heat-dissipating substrate such as aluminum or iron. The layer structure uses the soldering of the pins to directly transfer the heat of the chip package to the heat dissipating material, and even the concept of changing the coating material such as the insulating material or the solder resist ink to the heat dissipating material to achieve better heat dissipation. which performed. Strict heat dissipation requires a cost and safety dilemma These requirements are affected by the internal temperature of the LED luminaire product when it is actually used: the lower the internal temperature, the lower the temperature rating requirement for the heat dissipating material. However, the degree of heat dissipation depends on the material modification. The better the heat dissipation performance, the relatively expensive price of the material, which makes the company face the dilemma of cost and safety requirements. Obtaining market certification materials Certification obstacles and breakthrough points of LED heat dissipation substrate After obtaining the appropriate RTI, the board manufacturer must also make the appropriate samples, again perform the conductor tear strength at different temperatures, different widths, the layered bond observation and the flame resistance test of the coated solder resist material to determine the circuit. Board manufacturer's production capabilities. Under the proper polymerization conditions, the flame resistance of the heat dissipating material is usually unquestionable; as for the performance of other characteristics, it is a considerable test for the heat dissipating material. In spite of the requirements for new applications, in order to achieve the combination of copper foil and heat-dissipating materials, dimensional stability, temperature resistance and flame resistance, epoxy resin is compared with acrylic resin (Acrylic) or silicone resin (Silicon). It is also the most convenient modified matrix (Matrix). The heat dissipation capacity of the material is mostly through the addition of inorganic ceramic particles (non-conducting but heat-conducting, metal particles can not be used due to conduction) to achieve heat dissipation requirements; while the amount of addition and dispersion will affect the bonding of epoxy resins. Sex. In general, when the weight is added by more than 10%, not only the hardening property is not well mastered, but the bonding ability with the copper foil conductor is likely to fall below the standard, and even embrittlement or delamination directly occurs after baking. In the case of poor dispersion or particle shape imperfections, heterogeneous or anisotropic may occur. Although the nano-scale particle dispersion has been proven to reduce the amount of addition and maintain heat dissipation characteristics while reducing other environmental characteristics, the nano-scale particle cost is high, how can it be added to the viscous epoxy resin after a large amount of it remains The existence and dispersion of the meter level is also a challenge of high difficulty and high cost. in conclusion Gel Battery,Gel Cell Battery,Gel Battery For Car,Gel Type Battery Power X (Qingdao) Energy Technology Co., Ltd. , https://www.qdpowerxsolar.com
The release of safety standards means that the industry has a clearer safety specification to follow, and it has also prompted LED lighting companies to finally fully open their firepower and develop LED lighting products.
In addition to high-power LEDs, most LED luminaires must be designed into arrays of different shapes in order to achieve the same brightness as conventional luminaires. In order to meet the control requirements, the best way is to The LED chip package is soldered to the board. Since the LED illumination power to the heating power ratio is about 1:4, the matching circuit board must be different with the difference in LED power.
For example, low-power LEDs used in general flashlights or indications, because of the simple circuit and wide spacing, are generally phenolic paper substrates (Paper Phenolic® XPC, FR-1) or glass fiber impregnated epoxy substrates ( Fiberglass reinforced epoxy ∠FR-4) is sufficient to provide mechanical support and to dissipate heat through natural convection of the air for control purposes. In order to achieve high power and high illumination requirements, the increase in heat generation and the increase in circuit arrangement density will make the above substrate unable to provide sufficient heat dissipation capability.
The safety requirements of the luminaires, like pyramids, through the pre-selection mechanism, the selection of certified materials will reduce the durability test items required for the final product. Therefore, the materials in the LED module must pass the corresponding certification to ensure that the lighting products can be used for a long time without danger.
UL 8750 requires that the LED substrate must have the corresponding board temperature certification and flame resistance rating (listed in UL 796); the organic insulating material or coating material used for the board must also achieve the corresponding long-term use temperature. (or referred to as the Relative Thermal Index, Relative Thermal Index, RTI, listed in UL 746E) and approved for fire resistance rating.
The formulation of the heat dissipating material is mostly confidential or patented. Therefore, the difference in the heat dissipating substrate is very large. There is no way to use the same materials as the FR-1 and FR-4, which are widely used in the industry for a long time, and the versatility and characteristics are widely known. In addition, when obtaining a relative temperature index (RTI) higher than 90 °C, it is necessary to conduct long-term tests for 9 to 18 months or more, and even may not be able to obtain effective results at one time. The situation; together with the approval of the materials, it is necessary to carry out another 2 to 4 months of board production capacity recognition, for various reasons, the situation of long-term lack of material is not uncommon.
At present, there are only a handful of materials that have been approved for temperature resistance of heat-dissipating substrates in the world, and many of them are not large manufacturers. For a list of approved vendors, go to UL's public certification database (http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/index.html).
In addition to the insulating substrate material which has sufficient heat dissipation capability, other intermediate insulating material layers for bonding the copper foil line and the heat dissipating material must be subjected to temperature resistance test with the combined structure.
According to the standard, all the heat-dissipating insulation materials need to be analyzed for long-term thermal decay such as Dielectric, Tensile Strength, Delamination and Flammability. As for the composite structure combined with the heat-dissipating material, it is necessary to perform dielectric strength, constant-width conductor bond strength and heat-resistant thermal decay analysis.
LED heat-dissipating substrate maintains the development of high-efficiency LED lighting, but its technical difficulty and obstacles are no less than LED chip packaging. How to invest in the development of substrate materials in advance, how to overcome the safety problem of LED heat-dissipating substrates, will be to maintain the competition of China's LED lighting industry. The key to thinking is the key to avoiding.