Analysis of core technologies of LED packaging (Part one)

Flip chip packaging technology

Recently, the flip chip packaging technology, aroused heated debate in the industry, because the traditional dress process heat, depreciation and other technical bottlenecks encountered. The flip chip packaging technology, has invested heavily in research as early as 10 years ago, foreign companies, in order to free substrate glue, grain direct welding technology, not only can effectively reduce the thermal resistance, but also completely from the surface of the wire dress chip defects, let light tolerance to high temperature, prolong the service life of the LED. Industry generally believe that this is absolutely the forefront of the field of packaging technology. But people have to ask: after many years of research, why the flip chip technology can not replace the formal chip technology and become mainstream? The fundamental reason is the flip process depends not only on the ceramic substrate, but also on aluminum (copper) substrate, ceramic substrate processing and installation are not easy due to metal substrate, (two) after soldering to withstand the high temperature of 280 degrees, will inevitably cause damage to materials and components. Compared with the metal substrate, the reflection rate of the ceramic substrate is not high, and the transient light effect is difficult to improve, and the thermal conductivity of the ceramic substrate and the contact area of the chip are limited, and the steady light effect of the ceramic substrate is limited. Flip process two times and double resistance soldering ceramic substrate + aluminum substrate is sufficient to offset the advantages of lazy to do. In addition, the flip - chip technology of hot - pressing welding, reflow soldering equipment and other requirements are very high, yield instability. From the end user's point of view, a good LED should have better lighting quality, higher lighting performance, lower system cost and faster return on investment. Test the future prospects of flip chip technology (LM yuan) value. Quality first, the price is king, so causing the user to wait and see, product promotion difficult embarrassing situation.

Two, integrated COB packaging technology

In a sense, the core technology of LED packaging should be the development and manufacturing technology of packaging support, which determines the purpose, function and cost of LED light source. The strength of the company are trying to seek the use of packaging support to solve the LED heat dissipation, light efficiency, life, cost of the subject.

Compared with single chip packaging, COB packaging has many advantages, such as light intensity, heat dissipation, light distribution and cost, which is more and more regarded as the future development direction of LED. At present, the traditional COB light source is that the bracket is made of aluminum (or copper) substrate and the FR4 fiber board is pressed into a whole. Domestic FR-4 prepreg, the thermal conductivity is only 0.3/m-K, the best imported only about 2 /m-K, and the pure aluminum thermal conductivity is 237 /m-K, a difference of more than and 100 times, so the heat consumption ratio will increase the system resistance, resulting in serious LED decay, reduce the service life, is to try to get rid of people brains aluminum substrate this layer of insulating fiber, but has yet to find the effective method, such as some large companies design the so-called "LMCOB support" (dig in concave aluminum substrate remove copper and insulating layer), but limited to equipment, gel, process and cost and other reasons, has not yet been popularized. Also, the current market popular so-called "integrated light source" bracket, using plastic injection technology will be embedded in the PPA electrode plate (or are currently respected EMC) plastic, because PPA will become yellow in high temperature and ultraviolet radiation, caused by the air inlet, the failure rate is very high, because this structure is higher than that of the electrode plate the big chip 1.5mm, fluorescent powder and gel content, will not only increase the cost of the packaging and colloid too thick can affect the transmission, but also hardening crack breaking gold. At present, all COB support without exception must set up the dam structure, to prevent the overflow of mixed fluorescent glue, glue due to dam and surface oil absorption, can not achieve the specular reflection of light, the above reasons will affect the blocked light intensity and heat transfer, which is the main reason causing the difficulty to improve the traditional transient light effect the COB light source and steady light effect.