Mini/Micro LED generally refers to LED display technology with a chip size within 200/50um and a pixel pitch less than 1.0mm. With the continuous maturity of LED production and packaging technology, mini/micro LED display technology is developing rapidly. Mini/Micro LED display technology can be used in TVs, PCs, tablets, mobile phones, wearables, etc. As the application of advanced packaging technologies such as flip-chip continues to evolve, the packaging density of mini/micro LED significantly increases, while the pixel pitch is getting smaller and smaller. The complex packaging process poses a new challenge to solder. Fitech provides reliable solder and solution support for the mini/micro LED micro-photoelectric display industry.


Normally, the chips and the substrate have different thermal expansion coefficients. Therefore, the chips and substrate have different expansion amplitudes after die bond and reflow. For the pads with a size of dozens of microns, these differences in expansion have significant impacts on soldering. It is well known that thermal expansion increases with temperature. Hence, temperature increases will cause an expansion difference between the die-bond chip and the substrate. It is easy to cause misalignment of the pads in the reflow process because of high reflow temperature, leading to a series of reliability deficiencies such as open circuits and cold joint.

Mini LED 低温倒装固晶锡膏介绍

A fundamental solution to reliability deficiency due to thermal expansion coefficient differences is to use low-temperature solder materials which reduce peak reflow temperatures. SnBi/SnBiAg series solder is one of the most common low-temperature solders. The tipical melting point of SnBi/SnBiAg alloy is 139°C, which is nearly 80°C lower than that of SAC305.

Due to limitations of ultra-fine powder manufacturing technology, SAC305 is the main alloy used in ultra-fine die bond solders with the particle sizes of T7 and above. The low-temperature ultra-fine-pitch flip-chip die-bond solder paste developed by Fitech makes up for the blank of low-temperature ultra-fine lead-free solders. The low-temperature solder paste for die bond is made up of SnBiAg powder with the size of T7(2-11μm), T8(2-8μm), or T9(1-5μm) and a special flux, which effectively benefits the low-temperature soldering of ultra-fine-pitch die bond chip.

1. Product: Lead-free solder paste and lead-free epoxy solder adhesive;

2. Flux: No-clean, water-soluble , solvent-soluble; rosin resin, epoxy resin; 

3. Applications: Secondary reflow soldering with alloy melting temperatures of 139℃ and low-temperature packaging of Mini LED;

4. Type: T6-T9 (particle size:1-5μm);

5. Advantages: Reducing adverse impacts caused by thermal expansion difference and improving energy saving and environmental protection;

6. Disadvantages: Brittler solder joints than that of SAC products;

7. Processes: Printing, dispensing, needle transfer, and jet printing;

8. Reflow under nitrogen protection (reflow oxygen content ≤100ppm).

Related Products


Fitech’s tin-bismuth-silver alloy solder powder with excellent sphericity, uniform particle size, and low oxygen content is mixed with zero-halogen flux to prepare FT-574 series low-temperature solder paste. Solvent volatilizes very slightly during soldering. There is no solder ball formation. Only a tiny amount of residue generates after soldering. Moreover, FT-574 has excellent wettability. The solder joints formed are plump and bright. The product is suitable for low-temperature component mounting.


1. Excellent wettability, solder ball elimination, and wettability;

2. Outstanding thixotropy and appropriate viscosity for the processes of jet printing, pin transfer, dispensing, printing, etc.;

3. Superior printing performance and stencil life because of stable viscosity and tack time over 12 hours;

4. Extraordinary soldering performance and proper wettability in different parts;

5. Environmental-friendly product using zero-halogen formula.

FSA-574 series epoxy solder paste is formulated with SnBi series low-temperature ultra-fine solder powder with excellent sphericity, uniform particle size, and low oxygen content, and halogen-free flux. Only a tiny amount of solvent evaporates during the soldering and curing. There is no solder ball generation after soldering. The solder powder melts and shrinks, and the solder joints are metallurgical connections, which have soldering effects equivalent to that of solder paste. FSA-574 epoxy solder paste is unnecessary to clean after soldering. The solder residue becomes thermoset adhesive, which is attached around the solder joint to improve soldering strength, corrosion resistance, and insulation. FSA-574 is suitable for the reliable packaging of thin substrates and non-heat-resistance components.


1. FSA-574 can achieve metallurgical connection and have better thermal conductivity and electrical conductivity than that of silver conductive paste;

2. It does not require washing after soldering, and the residue becomes thermosetting adhesive to promote electrical insulation;

3. It has excellent chemical activity and solder ball elimination performance;

4. The operation is simple. Equipment such as reflow ovens, electric hot plates, and stoves can be used;

5. It has advantages of excellent thixotropy, appropriate viscosity, outstanding stability, no delamination, and long stencil life;

6. It has the functions of self-assembly and chip correction. When applying epoxy solder paste, the chip is automatically corrected when heating, and the solder automatically combines with the pad.

Our Engineers Will be Happy to Answer Your Questions or Help You Choose the Right Solder Product