Wave Soldering: Problems and Solutions

The process of designing Printed Circuit Boards (PCBs) includes a significant amount of soldering. Soldering is the only technique to ensure that your circuits cling to your board and remain there. Without appropriate J standard soldering, PCBs are of no use. Wave soldering is a form of soldering that is frequently employed in the mass production of PCBs. Manufacturers can now solder huge printed circuit boards fast and reliably using wave soldering technology.

Both the traditional through-hole and the more recent surface-mount methods of PCB assembly benefit from the wave soldering technique conducted under the J-STD-001 standard. One of the most basic components of a wave solder machine is a heated tank of solder that is kept at the right temperature for the particular soldering operation. As each PCB is passed through the tank, an oscillating wave of solder is set up inside the tank, which is subsequently passed along the bottom of the PCB.

Common Wave Soldering Mistakes & Fixes

• Hole Filling Not Enough

Insufficient hole fill is a concern on PCBs with pre-drilled holes for parts to be attached. In other words, when not enough solder has been used to fill the holes made for the components, the solder will not adhere to the circuit board after it cools. There are several reasons why a hole is underfilled.

• Due to improper flux application, the solder was unable to activate and bond to the components on the board.
• Solder cannot ascend through the holes because the temperature on the board’s topside is too low to melt it.
• The wave of solder did not cover enough of the board. Through-holes are filled with too little solder when there is not enough contact between the board and the wave.

Pre-solder tests are the best approach to correct these problems. Make sure the flux you’re applying has enough volume to cover the whole circuit board.

• Lifted Components

Components that have been lifted from the board, sometimes referred to as tombstones, have been raised from the board during the forging process. The following are some of the most prevalent causes of tombstones:

• Using the wrong amount of lead to the solder bath resulted in components lifting off the board.
• When wave soldering is attempted on a flexible PCB, the components lift off the board because the PCB bends while the components remain flat.
• Using a variety of components with different soldering needs and temperatures.

Look at the leads you’re using to rectify the wrong lead lengths. If your leads are excessively lengthy, they may be pushed out of the through-hole by the soldering bath. This may be remedied by increasing the in-wave immersion period, reducing the lead’s heat demand, and allowing for their settlement.

Verify your PCB’s thermal tolerances and type to see whether they are causing the flexing you are seeing. If so, replace the board. Big connections and large IC packages or sockets are the most susceptible to board bending. Weak or flexible PCBs like plastic should not be wave-soldered to prevent components from being lifted from the board and damaged.

As the last step, evaluate the thermal tolerances of all your components after checking your board. Components with varying temperature requirements or lead solderability temperatures may also lift in response to contact with the wave, as some elements solder down while others are pushed away by the excess heat. To avoid these kinds of problems, it’s essential to ensure that all the components you’re employing are compatible.

• Excessive Solder

When your board passes through a wave-solder tank, it accumulates a solder buildup, resulting in excessive solder. The board and component will still be connected electrically, but it will be difficult for you or anybody else looking at the board to identify precisely what is going on within it.

To reduce the amount of solder needed, it is recommended that erroneous lead lengths be corrected during the design phase. As a result of excessive solder pooling, the length of the lead might be reduced. Choose a lead length that doesn’t extend over your pad surfaces if you want to fix this problem. Typical lead lengths for NASA include 2.29 mm, which is just long enough to extend over the solder pads.

• Solder Flags

A solder flag is a little piece of solder that protrudes from the end of your wires to indicate a connection has been made. When the solder wave separation from the board is not controlled properly, slow draining is the result. Improperly cut or kept leads might cause oxidation. Your supplier should be able to tell you how they cut their leads if you don’t cut your own. If your leads are stored for an extended period of time with bare-cut ends, this might cause them to oxidize.

Leads that are cut and held in-house provide you with greater control over how they’re done and how long they’re kept in stock. Since the lead is exposed to oxidation in all three of these ways, soldering the piece becomes more challenging.