Conveyor Angle in Wave Soldering

As technology advances, pcb assembly near me become more complicated with a variety of through-hole and surface mount components. These advanced circuit boards (PCBs) require a more complex set of assembly and test operations to verify proper operation. With each advancement comes a new challenge for the specialized equipment used to assemble them, including wave soldering machines.

Early wave machines had a simple concept: plates (“baffles”) in a tank of molten solder forming a flat asymmetrical wave with flow over the front and back of the wave. Providing all multileaded devices were correctly oriented to enter the wave head-on and that large pin count connectors remained behind larger pin count components to avoid shadowing, soldering nirvana was reached.

Unfortunately, asymmetrical waves have their limits. With the advent of surface mount devices (SMDs), problems such as excess solder and solder skips became dominant issues in wave soldering. Even the flat wave and angled conveyor could not prevent them. These serious defects led to expensive, time-consuming, and error-prone touchup operations.

In addition to component, design, and tooling factors, the wave solder process can also contribute to these defects. Many of these defects are related to the conveyor angle and/or turbulence in the flow. Optimizing the conveyor angle can reduce these defects.

Splash back is a common problem that can be caused by too much rosin in the flux, high conveyor speed, or poor PCB transfer. This may result in a high level of tin oxide and slag on the PCB surface, which is not conducive to soldering. It can also be caused by uneven heating of the PCB or the transfer frame.

Optimizing Conveyor Angle in Wave Soldering

Solder skips are another problem that can be caused by the wave height being too high or excessive turbulence in the flow. It can also be caused by areas of entrapment on the pallet, requiring a review of the pallet design to ensure there are sufficient flow channels for the solder.

The optimum conveyor angle is 60deg, which provides an optimal incline for the squeegees to print solder paste onto the stencil. Using an angle too steep can cause the blades to scoop the paste out of the stencil apertures. This can lead to insufficient paste coverage and an insufficient number of solder joints.

The optimum conveyor angle is the most critical factor in minimizing solder skips. It should be determined in advance with the help of a computer model of the machine and the layout of the populated PCBs. This information should be provided in the form of a BOM and Gerber files for each job. The BOM should include a list of parts with the part name, part number, and the PCB footprint.

It is recommended that a DO NOT POPULATE file be included in the BOM for any parts that should not be soldered on the board. This should be used to help minimize the risk of soldering unwanted parts and saving production time. The Gerber files should be checked to make sure they are accurate and that the part name and footprint match.