What are the regulations for lead-free environmentally friendly solder paste? Why has it dried out? How to deal with it? At present, most companies choose lead-free processing technology. As an important part of lead-free processing technology, lead-free environmentally friendly solder paste has increasingly drawn our attention due to its performance characteristics. In fact, it depends on the main matters you have in this regard. It's very mysteriousLead-free solder pasteTo dry out, we can look at it from two aspects. Now, let me, Jia Jinyuan, explain it to you all:

For instance, if the ancestral secret recipe is poor or the temperature is too high, the organic solvent will evaporate very easily. When the relative humidity of the air is too high, the solder paste will absorb moisture and react with the rosin in the solder paste, causing it to dry out. Considering the ancestral secret recipe, it is generally unlikely that it is due to the use of aldehydes. There are indeed some solder pastes that use aldehydes, but it seems that alcohol has never been seen. More often, ethers are used.

Second, there is also a claim that it is due to the organic solvents in the flux formula of lead-free environmental protection solder paste. If the flux used in the production of solder paste is an organic solvent that is very easy to evaporate, of course, the solder paste will gradually develop during application. Little do people know that there are many factors contributing to the roughness of solder paste. The reasons for the roughness of solder paste in the flux operation management system are as follows: 

1Rosin, the proportion of rosin in the flux increases. If it is unstable, it will simultaneously affect the stability of the flux. If rosin with poor heat resistance is used to make solder paste, it is very easy to mold under high temperature conditions, thereby affecting the probability of the solder paste drying out. 

2Organic substances, antioxidants, surfactants, etc., when added in small amounts, the expected effect can be said to be relatively large. The expected effect of lead-free solder paste soldering will directly depend on them. 

3Organic solvents, such as aldehydes, are used as organic solvents. Before the flux is made into lead-free solder paste, its viscosity is very likely to increase and then it will change. Take a paranoid example: Using industrial ethanol (for material testing), it can be said that organic solvents are of crucial importance. 

4Thixotropic agent, the increase in the amount of thixotropic agent is also quite large. It has the function of an emulsion flux in it, using chemical reactions to produce compressibility, ensuring that the compressibility of continuous repair is maintained throughout the solder paste replacement process. If it encounters problems and affects the compressibility, it will of course have an impact on the viscosity of the solder paste. If the viscosity increases, it will be found that the solder paste has either changed or hardened. 

Nowadays, most of the products are based on the research and development of lead-free ring solder paste. We have delved into many problems caused by lead-free processing techniques, such as aluminum alloy selection, printability, low-temperature reflux, and crack levels. At the same time, we will introduce the corresponding features of the first generation of lead-free solder paste products to everyone.
  1.Packaging printability
  BecauseSn/Ag/CuThe density of the alloy(7.5g/mm3)thanSn-PbThe density of the alloy(8.5g/mm3)The packaging and printing performance of lead-free solder paste made of this aluminum alloy is slightly worse than that of leaded solder paste,Such as it is very easy to stick to the scraper, etc. Even so, because ensuring the better packaging printability of the solder paste is aimed at improvingSMTProductivity and cost control are of great significance. Under the condition that the composition of aluminum alloy is the same, only by adjusting the composition of the flux can the printability of the solder paste be improved, such as the ability to fill the mesh, wet strength, and cold resistance/Thermal collapse and the ability to work in damp and cold natural environments, etc., thus enhancing the printing speed of packaging and achieving the actual printing effect of packaging.
  2.The necessity of flowing back 

Because the melting point of lead-free alloys rises.Sn/Ag/CuThe melting point of the alloy is217°C,Sn-PbThe melting point of the alloy is183°CThe main problem encountered by lead-free processing technology is the increase of the maximum temperature in the reflow soldering furnace . When lead-free environmentally friendly solder paste flows back into the electric soldering process, it is generally assumed under very bad conditions (pcbThe circuit board is complex, the system deviation and data error are positive, and it meets the standard of sufficient immersion.pcbThe temperature at which the network hotspots on the circuit board are likely to be achieved265°C"

3.Selection of aluminium alloy

In order to better find a suitable lead-free aluminum alloy to replace the traditional oneSn-PbAluminum alloy, many attempts have been made by everyone. This is because there are many factors to consider when choosing lead-free aluminum alloys, such as melting point, impact toughness, shelf life, and cost. 

4.Crack level 

Cracks are a common defect in flow back welding, especially in the pastBGA/CSPThe presentation on electronic devices is particularly prominent. Due to the significant differences in the size, location, proportion of cracks and their precise measurement fields, the safety assessment of crack levels has not been unified so far.

ShenzhenJJYWell-known brand solder paste, experience12A solder paste and solder wire manufacturer specializing in the annual research and development of solder paste, solder wire, solder wire, lead-free solder paste, leaded solder paste, solder rods, leaded solder paste, etc. For solder paste, choose the well-known brand of JJY as the solder paste manufacturer.