The quality of solder paste will directly affect the soldering quality of electronic products, as almost all electronic components have gone through it nowadaysSMTProcess, circuit board(PCBAll are connected through solder paste, so it is very important to choose a solder paste suitable for the company's products. Generally, the selection should be based on different usage scenarios:

1ConsiderPCBAnd the temperature requirements of the components, as well as the number of reflow ovens.

Commonly used solder pastes includeSn63Pb37andSn62Pb36Ag2. For components with palladium or silver thick film terminals and pins that have poor solderability, silver-containing solder paste should be selected, while for water gold boards, silver-containing solder paste is not suitable.

2According toPCBThe requirements for cleanliness and different cleaning processes after reflow soldering are selected:

When using the no-cleaning process, no-cleaning solder paste that does not contain halogens and strong corrosive compounds should be selected.

When the solvent cleaning process is adopted, solvent-cleaning solder paste should be selected.

When using the water cleaning process, water-soluble solder paste should be selected.

BGA,CSPGenerally, high-quality no-clean silver-containing solder paste needs to be selected.

3According toPCBSelect the activity of solder paste based on the storage time of components and the degree of surface oxidation:

Generally adoptedkJRMAGrade;

High-reliability products, aerospace and military products are available for selectionRGrade;

whenPCBWhen components are stored for a long time, their surfaces will be severely oxidized and should be adoptedRAAfter the welding is completed, cleaning treatment should be carried out.

4,SMTWhether the assembly density has a narrow spacing will affect the selection of the alloy powder particle size of the solder paste. There are usually four particle size grades. If there is a narrow spacing, it is generally chosen20-45Micron powder particles.

5The viscosity of the solder paste should be selected based on the process of applying the solder paste and the assembly density. High-density printing requires high viscosity, while drop coating requires low viscosity.

6Select according to environmental protection requirements. For lead-free processes, solder paste containing lead cannot be selected.

As the volume of electronic components is getting smaller and smaller, it can be used now0402The components need to be tested in a high-temperature and high-humidity environment. Therefore, when selecting solder paste, special attention should be paid to checking its surface insulation resistance(SIRThe performance of the value.

The phenomenon of electron migration occurs when there is a potential difference between adjacent ends. Metal conductive substances (such as tin, silver, copper, etc.) grow from one end of the electrode to the other in a neuro-like manner. If the flux has a slight conductive ability, especially under high temperature and high humidity conditions, it will produce an electron migration phenomenon at its adjacent ends because the medium in which it grows is a conductor.

After printing the solder paste on the bare copper plate and reflow soldering it, place it in40°C+93%RHIt persists in the (humidity) environment10On a certain day, a copper corrosion test was conducted to observe its corrosion condition.

【 Tin Ball Testing 】 Strictly speaking, there are two types of tin balls. One is the micro-tin ball.micro-solderballThe other one is tin beads(solderbead"

In that case, buy itSolder pasteIt is best to buy a small amount of solder paste in advance to check if it is suitable for your product, so as to avoid mistakes.