Precautions for use of lead solder paste and purchase of lead solder wire

Precautions for use of lead solder paste and purchase of lead solder wire

The circuit board manufacturer and circuit board designer will explain the precautions for the use of lead solder paste and the purchase of lead solder wire.

Usage and precautions of lead solder paste

Lead solder paste is an indispensable welding material in the SMT processing industry. Lead solder paste is a mixture of soldering components and alloy components. Among the alloy components, tin and lead are the main components, so it is called lead solder paste.

1、 Usage

1. The lead tin paste must be heated to about 25 ℃ before use. It is prohibited to heat during the heating process, as long as it is placed at room temperature. At the same time, manually mix for 3-5 minutes or use a mixer for 1-3 minutes after the temperature is restored.

2. Invert 2/3 of the amount of solder paste on the steel plate, and add a small amount of solder paste several times according to the production situation.

3. The unsealed solder paste should be used within 24 hours. Try not to put the poured solder paste back into the tin paste tank.

4. After the solder paste is printed on the substrate, it is recommended to mount the components and enter the reflow soldering to complete the welding within 4-6 hours;

5. During the solder paste welding process, in order to obtain the best welding effect, the room temperature should be controlled at 22~28 ℃ and the humidity RH40~60%.

6. It is recommended to use ethanol and IPA to clean the printed wrong substrate.

2、 Precautions

1. Only take out enough solder paste for each use, and then cover it immediately.

2. After the inner cover is covered, press down hard to squeeze out air, and then cover the outer large cover.

3. Do not stir when the solder paste surface has skinned and hardened. It shall be removed and used after passing the inspection before next use.

4. Excess solder paste taken out should be specially recycled in a bottle. At the same time, save according to Note 2.

5. The solder paste taken out shall be printed as soon as possible. The printing work should be continuous and should not stop printing.

Selection and discrimination of lead solder wire

Lead solder wire can be divided into different grades, different prices and different effects according to its tin content.

1、 Purchase and distinguish solder wire

1. Tin content

Tin content is the only standard to judge the grade of solder wire. It is an important factor related to welding effect, firmness, reliability, conductivity and other indicators. When purchasing solder wire, lead solder wire should be used according to the requirements of relevant products, which can ensure the welding quality. However, the tin content needs to be measured, such as by spectral detector, chemical titration, etc.

2. Package appearance and weight

Although the packaging appearance can not accurately reflect the quality of the tin wire, normal electronic manufacturers will generally give standard descriptions of the solder wire when they reproduce the tin wire, explaining the relevant specifications of the tin wire, so that buyers can distinguish between them. At the same time, the weight of solder wire is different, and the price is also different.

3. Lustrous color

The luster color is directly related to the quality and tin content of the solder wire. The brighter the luster, the higher the tin content, and the better the welding effect.

4. Residue and smoke concentration

The solder wire will leave residue and smoke when used. The less smoke, the less residue. The effect of welding spot will also be better. In addition, the smoke generated by the lead solder wire will affect the health of the operators, so the lead solder wire with less smoke residue should be selected.

The Circuit board manufacturer and circuit board designer will explain the precautions for the use of lead solder paste and the purchase of lead solder wire.