High-power LED Die Attach Solder Paste

At present, the high-power LED, particularly the white LED, has been industrialized and forward to the general lighting market. There has put forward high requirements to the power –based LED packaging technology. As the continuous improvement of input power of LED chip.

The power-based LED packaging technology should meet the following two points: first, package structure should be taken with high light efficiency, the second is the thermal resistance should be as low as possible. For large operating current of the power LED chip, low thermal resistance, good heat dissipation, and the new low-stress package structure is the technology key of the power-based LED devices.

The solder paste are generally used for metal welding, the thermal conductivity is 67W/m.k or so, is much more than commonly used electrically conductive adhesive. Thus, in the field of LED wafer packaging, the ultra-fine solder paste can replace the existing packaging materials as thermally conductive adhesive and electrically conductive adhesive, thereby achieve better thermal effects, and significantly reduce the packaging costs.

Shenzhen earlysun technology through a long period of R&D and testing, has developed the die attach solder paste with high thixotropy and low viscosity .this solder paste is not only a high thermal conductivity, small resistance, quickly heat, also can meet the cooling needs of LED chip, and the quality of solid crystal is stable, the strength of welding mechanical is high, can effectively guarantee the reliability of die attach. The specific parameters are as follows:

Thermal conductivity

The thermal conductivity of main alloy SnAgCu of die attach solder paste is 67W/m.k or so, small resistance, quickly heat, can meet the cooling needs of LED chips (thermal conductivity of commonly used electrically conductive adhesive is generally 1.5-25W/m.k).

Chip size

The powder diameter of solder is 10-25μm(5-6#powder),can effectively meet the welding of the high power chip between 5 mil-75 mil（0.127-1.91mm）.

Die attach process

Prepaire adhesive, dip adhesive and dispensing, die bond, eutectic welding.

The dispensing cycle of die bonder can up to 240ms, the die bonding cycle is 150ms, and the speed is quick and the yield is high.

Welding performance

Repeat dispensing with stand a long time, the solder point full bright, empty rate is less than 5%, reliability of the die bonding is good and the quality is stable.

Thixotropy

Using the uniform ultra-fine solder powder and high thixotropy paste, the thixotropy is good, doesn’t cause chip drift. Low viscosity, for 10000-25000cps, and we can adjust the size according to the dispensing speed.

Residue

It has very few residues, put the die attached LED in thermostat, 240 hours after, the residue and base metal does not change color, and does not affect the LED glow.

Mechanical strength

The strength of welding mechanical is higher than electrically conductive adhesive, without damage and chip drop phenomenon when the solder joints under 10 N thrust.

Welding method

Reflow or desktop reflow, set the reflow temperature at the alloy eutectic temperature directly, the welding solid die attach can be finished within 5 min, while the electrically conductive adhesive is generally 30min, to reduce power consumption of die bonding.

Alloy selection

Customers can choose the suitable alloy according to their own requirements, SnAg3Cu0.5 lead-free solder paste can meet the ROHS directive requirements, the melting point of SnSb10 is 240-250℃,meet the needs of returning LED packaging requirements, its thermal conductivity is close to alloy SnAgCu0.5.

Cost comparison

In the bonding materials, meet the cooling needs of high-power LED thermal conductivity, the cost of die attach solder paste is lower than electrically conductive adhesive, and Au80Sn20 alloy, and the die attach process can save energy.