1. Application of copper solder paste

There are three main methods for applying solder paste: injection droplet application, screen printing, and stencil printing.Copper solder paste manufacturersIt is noted that injection droplet application is done using a specialized dispenser or manually, using barrel solder paste, which is generally suitable for small batch production. Screen printing uses nylon or stainless steel wire materials to create a mesh, with patterns etched on it to apply solder paste onto the PCB, typically suitable for medium to small batch production with lower assembly density. The most commonly used method is stencil printing, which uses brass or stainless steel plates with patterns etched on them to print solder paste onto the PCB. Here we introduce the method of using solder paste when employing stencil printing.

1. Based on the size of the printed circuit board and the number of solder points, determine the amount of solder paste to be added to the stencil for the first time, generally adding 200-300g of solder paste strips (ensuring the rollability of the solder paste strips), and then adding a little more after a period of printing.

2. The temperature for solder paste printing should be 25±3℃, with a relative humidity of 60% being ideal.Copper solder paste manufacturersIt is noted that if the temperature is too high, the solder paste can easily absorb moisture, leading to solder balls during reflow soldering.

3. If the solder paste has been on the stencil for more than 30 minutes without use, it should be stirred using the stirring function of the screen printer before use.

4. The key to applying solder paste onto the printed circuit board is to ensure that it accurately covers the pads of the components. If applied inaccurately, the solder paste must be wiped off and reapplied (do not use alcohol to clean no-clean solder paste).

2. Recovery of copper solder paste

If there is a long interval in between, the solder paste should be returned to its container and tightly sealed until it is used again. In principle, opened solder paste should be used up within the same day. Solder paste scraped back from the stencil should also be sealed and refrigerated.

3. Other aspects of copper solder paste

Circuit boards with printed solder paste should have components mounted in a timely manner; if too much time has passed, the solder paste should be cleaned off and reapplied. Completed mounted circuit boards should ideally undergo reflow within 4 hours. Circuit boards requiring cleaning after reflow should be cleaned on the same day to prevent residues from corroding the circuit.