Tuesday, 13 January 2015

Mount A Circuit Board

Anti-static precautions are appropriate as some components are static sensitive.

Mounting an electronic circuit board requires precision, skill with hand tools, patience and a working knowledge of the circuit to be mounted. Results may vary. Safety is the responsibility of the individual doing this work. See the Link "Hand and Power Tools" for OSHA (Occupational Safety and Health Administration) safety recommendations. Also note the warnings below.


1. Gather critical dimensions. Measure the longest distance any circuit component extends above, below or to any side of the circuit board and record for future use. Measure the circuit board length, width and thickness, and record for future use.

2. Determine standoff height. Add 1/8-inch to the distance that any circuit component extends below the circuit board. Pick the next largest length of standoff. You will need one standoff for every four square inches of circuit board, plus one for each corner. If the circuit board has an irregular shape (i.e., not a rectangle or square), order a standoff for each 90° angle present.

3. Determine the standoff type. A 1/4-inch 4-40 aluminum standoff of the appropriate length is usually a good choice. They are cheap, sturdy, and pose minimal corrosion problems. A 6mm hex standoff is the metric equivalent. If the circuit board does not allow at least 3/4-inch (2mm) of clearance for the aluminum post and nut (or screw). use an insulated standoff for that position.

4. Locate the positions for each standoff. A standoff may be located in a ground plane (wide areas of circuit ground) if the case is plastic. This is also allowed in metal cases if the case is also circuit ground. Each aluminum standoff must have at least 3/4-inch (2mm) of clearance from all electronic circuit components or their connecting traces.

Use an insulated standoff where this is not possible. Use the ruler, pencil and any identifiable circuit board locations to mark standoff locations for drilling.

5. Drill a hole for each standoff. For a 4-40 screw, you would use a 0.120-inch drill bit or #31. Substitute a 3/32-inch drill bit if only fractional sizes are available. A 3/32-inch drill hole will need widening. Be careful not to damage the circuit board or electronic components during this process.

Alternatively, a 1/8-inch drill bit could be used, but the hole may be too big, depending on the mounting hardware used. Mount standoffs to circuit board. Place each standoff in its proper location. Secure it with its matching hardware.

6. Locate standoff positions on case or mounting platform. When choosing a place to mount the electronic circuit board in the case, consider both physical and electrical/electronic requirements. If there are components that require contact with the case for heat sinking or other electrical or electronic requirements, these considerations may modify a purely physical consideration.

While the circuit board must fit, it must also function as an electronic device. Similarly, if there are components that require isolation from the case, this too must be considered. Once an appropriate position has been found, mark the bottom of each standoff with the pencil.

7. Drill holes in the case or mounting platform for each standoff. For a 4-40 screw, that would be a 0.120" drill bit or #31. Note substitution information as stated in Step 5. Mount standoffs to case or mounting platform. Place each standoff in its proper location. Secure it with its matching hardware.

Tags: circuit board, each standoff, case mounting, case mounting platform, electronic circuit