PCB Tech - PCBA: Placement of parts during wave soldering

Design specifications for the placement of parts during wave soldering

When PCB circuit boards first came out, they were almost always designed with traditional INSERTION at the beginning. At that time, all boards had to go through wave soldering. At that time, the boards were only single-sided; later, after the invention of PCB, At the beginning, there was a mixed use of SMT and wave soldering. At that time, a large part of the parts could not be converted to the SMD process. That is to say, it was necessary to mix the traditional plug-in and SMD parts. The steps of hand plug-in, and then go through the wave soldering furnace. Because of the need for such a process, the design of the board must arrange all the plug-in parts on the same side, and then use the other side for wave soldering, and the wave soldering side The SMD parts must be fixed with red glue to avoid the problem of parts falling into the tin furnace during wave soldering.

Since the wave soldering process will have a panel soaked in the molten liquid tin furnace, there will be many restrictions on the design and manufacturing of the circuit board. In addition, there will be some parts that cannot be designed on the surface of the tin furnace. Try to summarize and list some rules you know:

1. For areas that need to be wave soldered, the vias are preferably plugged to avoid overflowing tin to the part surface when passing through the wave

soldering furnace, causing unpredictable short circuit problems.

2. For parts with rows of feet, the straight line of the rows of feet should be parallel to the squareness of wave soldering, so as to avoid short circuits between the rows of feet, and to make the tin better.

3. If there are small parts such as resistors, capacitors, inductances and the like of PCB parts that need to be wave soldered, the parts should be perpendicular to the direction of wave soldering.

4. If there is a SOIC (IC with solder feet on both sides of the part), the entire row of solder feet should be parallel to the wave soldering squareness.

5. Please note that only single-row or double-row soldering foot parts have the opportunity to undergo wave soldering, and other parts with four-sided soldering feet are definitely not suitable for wave soldering.

6. In order to avoid shadow effect, taller and larger parts should be located behind the wave soldering direction.

Suggestions for the hand-soldering of hand-plugs during wave soldering (these rules were originally given for a board with more than 10 hand-plugs on it, but I think it should also be applied to some selective wave soldering boards):

1. Insert tight fitting parts first, such as some connectors with bent feet to communicate with the outside world, so as to avoid shaking off other first inserted parts due to vibration when inserting tight fittings.

2. When plugging in, the plug-in position of the right hand should be arranged from upper left to lower right; the plug-in position of the left hand is from upper right to lower left to avoid parts blocking gesture actions.

3. The order of the plug-in should be from the lower parts first and then the higher parts to avoid the higher parts from obstructing the hand. (For example, the resistance between the two connectors)

4. It is best to arrange the same PCB parts to be inserted in the same station. (Reduce the chance of inserting wrong positions and wrong parts)

5. It is best to concentrate the hand-inserted parts of the same PCB operator in one corner, so that the operator's eyes can be concentrated in the same area, and errors can be avoided.

6. Parts with the same appearance but different material numbers should be avoided in the same station to avoid confusion.

7. Parts with polarity should not be arranged in the same station as far as possible. Otherwise, the same workstation will be too heavy.

8. Each station should strive for the same working hours.