PCB Wave Soldering Services

PCB Wave Soldering

Wave soldering is a large-scale soldering process by which electronic components are soldered to a printed circuit board (PCB) to form an electronic assembly. The name is derived from the use of waves of molten solder to attach metal components to the PCB. The process uses a tank to hold a quantity of molten solder; the components are inserted into or placed on the PCB and the loaded PCB is passed across a pumped wave or waterfall of solder. The solder wets the exposed metallic areas of the board (those not protected with solder mask, a protective coating that prevents the solder from bridging between connections), creating a reliable mechanical and electrical connection. The process is much faster and can create a higher quality product than manual soldering of components.

Wave soldering is used for both through-hole printed circuit assemblies, and surface mount. In the latter case, the components are glued by the placement equipment onto the printed circuit board surface before being run through the molten solder wave.

Comparison between Wave Soldering and Reflow Soldering

As contemporary electronics embraces light weight, high speed and increasing efficiency, each link of manufacturing thereafter conforms to such philosophy, which is open to Printed Circuit Board Assembly as well. Soldering has been playing an essential role in determining the success of electronic products since electrical connection achievement derives from precise soldering. Compared with hand soldering that’s still preferred by some electronics hobbyists, automatic soldering has been widely selected due to its merits of high accuracy and speed and demands of large volume and high cost-effectiveness. As the leading soldering technologies for assembly, wave soldering and reflow soldering have been most widely applied to contribute to high-quality assembly. Nevertheless, they are always being mixed up and differences between them tend to confuse many and when to use them is even vague.

PCB Wave Soldering Process

Wave soldering process is composed by four steps: flux spraying, pre-heating, wave soldering and cooling.

Step one: Flux Spraying. Cleanliness of metal surface is the basic element ensuring soldering performance, depending on functions of solder flux. Solder flux plays a crucial role in smooth implementation of soldering. Leading functions of solder flux include:

  • To eliminate oxide from metal surface of boards and components’ pins;
  • To stop circuit boards from secondary oxidation during thermal process;
  • To reduce surface tension of solder paste;
  • To transmit heat.

Step two: Pre-heating. In a pallet along a chain similar to conveyor belt, PCBs travel through a heat tunnel to carry out pre-heating and activate flux.

Step three: Wave Soldering. As temperature constantly rises, solder paste becomes liquid with a wave formed from whose edge boards will travel above and components can be solidly bonded on boards.

Step four: Cooling. Wave soldering profile conforms to a temperature curve. As temperature reaches the peak in wave soldering stage, its reduction comes, which is called a cooling zone. After being cooled to room temperature, board will be successfully assembled.

Step four: Cooling. Wave soldering profile conforms to a temperature curve. As temperature reaches the peak in wave soldering stage, its reduction comes, which is called a cooling zone. After being cooled to room temperature, board will be successfully assembled.

As circuit boards are placed on pallet ready to go through wave soldering, time and temperature are closely associated with soldering performance. As far as time and temperature are concerned, a professional wave soldering machine is of much necessity while PCB Assembler’s expertise and experience are seldom easy to obtain since they depend on years’ accumulation, application of up-to-date technologies and business focus.

If temperature is set to be too low, flux won’t be melted so that it won’t maintain activity, reaction capability and capabilities to dissolve oxide and dirt on the surface of metal. In addition, alloy won’t be generated by flux and metal if temperature is not sufficiently high. Furthermore, other factors such as speed of band carrier, wave contact time etc. should be taken into considerations and calculation.

Generally speaking, even though the same wave soldering equipment is applied, different Assemblers possibly feature different manufacturing efficiency due to different operation methods and extent of understanding on soldering machine. For example, East India Technologies (a India-based full turnkey PCB Assembly service supplier) engineers take advantage of fixture to fix THT components prior to wave soldering so that all parts can be accurately mounted on boards with soldering defects dramatically decreased.