Mastering PCB Soldering: Types, Techniques, and Best Practices

May 28,2021

Soldering is a metal fabrication process that is used for fuse-and-connect two metals. This technique is extensively adopted in the PCB fabrication processes to fix the mounted components on the circuit boards. Traditionally, soldering included a mixture of tin and lead as the solder. With growing concerns over the toxicity of lead, nowadays, lead-free soldering is promoted. Also, lead-free soldering allows PCB manufacturers to comply with the Restriction of Hazardous Substances (RoHS) directive i.e.; 2002/95/EC. Besides the solder material considerations, the PCB soldering process differs in multiple aspects like types and methods adopted to perform PCB soldering. This post discusses different types of PCB soldering processes followed by a few tips to enhance process efficiency.

Different Types of PCB Soldering Process

Soldering is an integral part of both surface mount and through-hole PCB fabrication processes. The following types of PCB soldering processes are adopted according to design and fabrication parameters.

• Wave Soldering:

  Wave soldering is the traditional type of PCB soldering process, which was ideally introduced for through-hole PCB fabrication. In this process, the flux is sprayed over the PCB and is then passed through one or more waves of solder. Although it is ideal for through-hole mounting, it can be utilized for surface mount types of PCBs. It is often utilized for double-sided SMT PCBs.

• Reflow Soldering:

  Reflow soldering is a comparatively new technique of the PCB soldering process. In this type of soldering, the solder balls are suspended in flux and then deposited on the stencil-covered PCB. The stencil prevents the solder-paste from covering the locations where no parts are to be mounted. Once the targeted solder-paste application is done, the PCBs are passed through the oven which causes the solder balls to melt. Further, the PCBs are left to cool naturally so that the solder-paste fixates with the mounted components.

• Selective Soldering:

  Selective soldering is the latest PCB soldering process. In this technique, a precise solder-paste application is done by accessing data from the CAD files. This helps in performing laser-targeted and high-quality soldering.

Out of the above-mentioned types of PCB soldering processes, the PCB contract manufacturers (CMs) choose the one based on requirements.

However, the PCB soldering and fabrication processes are subjected to defects like cold solder joints, tombstoning, etc. In order to prevent certain defects and achieve efficient PCB soldering, the following tips may be helpful.

Tips for Error-Free PCB Soldering

The following tips can be helpful in ensuring the quality of the PCB soldering process.

• While performing soldering for through-hole PCB fabrication, aim for concave fillet at the joining point.

• To prevent the solder bridging, hold the solder gun at the center of the bridges and allow the solder paste to melt. If the solder bridge is too large, then the solder sucker can be used to remove excess solder paste.

• To prevent cold or overheated solder joint, the solder paste must be applied at a suitable temperature and allowed to cool at room temperature.

• Tombstones can be prevented by adopting a thermal relief design during the PCB layout stage itself.

• Reduce PCB exposure to moisture during the soldering process.

In order to get defect-free, highly efficient PCBs, you must partner with an experienced PCB contract manufacturer like Creative Hi-Tech. The company offers high-quality PCB fabrication services with state-of-the-art equipment to perform high-quality soldering and fabrication processes. Having a well-equipped facility with automated pick-place component mounting, reflow and wave soldering, and choice of RoHS compliant solder material selection, the company is capable of offering quality PCB fabrication services.

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