Radius of about 5.0mm at the board corner

Adding radius at the board corner has the following advantages.

• Prevents injuries during handling of the board due to sharp edges
• Prevents damage to other boards and objects during the manufacturing processes
• Prevents component loss due to sharp edges is easier to trapped in the transfer line during assembly
• Prevents chipping and damage to packaging materials due to impact and vibration during transportation

Radius of 5.0mm is recommended. Smaller radius may not prevent the above phenomenons. Consider adding radius at the corners of both breakaway board and the  main boards.

• Radius at the main board and breakaway board.
• Set radius as large as possible. Recommended is 5.0mm

The benefits of adding a breakaway boards

• Prevent boards from being damaged during manufacturing, packaging and shipping processes
• Make it easier to support mounter mounting
• Machining guide holes, mounting recognition marks, reference holes, sub-reference holes, and radius corner can be placed at the breakaway board.

Breakaway boards are not only useful for positioning and mounting, but also useful in  protecting the main board. It is recommended to design the breakaway board in the longitudinal direction of the board related to the mounting of the board to the transfer line.. 
Though it may increase the board area and costs, it will be insignificant if the yield and quality of the board can be control consistently during production.it is a very effective way to stabilize quality. Please consider adding a discarded board.

• The width of the discarded board is usually around 10.0 to 20.0 mm.
• It is a good idea to add solid copper foil that is divided into discarded substrates to prevent warping and expansion / contraction.

Recommended Size and Positions

- Size: φ2.05mm (NTH) or φ1.55mm (NTH) 

- Placement position: 

- 2x Holes on the board around the edge 

- 1x for preventing reverse loading

- Holes should be placed asymmetrical to prevent wrong orientation

- Approximately 5.0mm from the board edge

- Extra holes maybe required to hold on to the main boards during cutting process enabling the routing process to remove the breakaway PCB.

Reference hole / sub-reference hole to be used in the mounting process.

Recommended Size and Positions

Hole diameter: φ4.0mm (NTH) 
Sub-reference hole: φ4.0x5.0mm (LNTH)
Placed horizontally with respect to mounting flow directions

Advantages.

• This is the reference hole for mounting the board to the mounter.
• Fix the board and prevent mounting displacement
• Used as a “reference hole for positioning” when inserting lead parts using an automatic insertion machine

The secondary reference hole is an ellipse in consideration of dimensional shrinkage of the board. There are SMD component mounters that do not require a “reference hole / sub-reference hole”, but there are many mounter devices that use positioning reference pins and transfer pins in the mounter. 

5 Fiducial Mark

Fiducial mark is used to align the board with the auto insertion machine.

Recommended Size and Positionsattern size:

Pattern Diameter φ1.0 mm 
Resist opening size: φ3.0 mm
Guard pattern: Ring with outer diameter of φ3.9 mm, inner diameter of φ3.3 mm 
Positions: 2 on the PCB, 1 for preventing reverse loading 3 or more for location
Placed in asymmetrical position

For narrow pitch parts with a pitch of less than 0.5 mm or parts with leads under the package, such as BGA, fiducial mark is added to the individual part to improve the mounting accuracy. 
The placement position should be asymmetric to prevent incorrect mounting on the front and back surfaces, so that they do not overlap even if they are turned over or rotated 180 degrees. Component mounting errors are prevented.

In order to prevent the mounting recognition mark from disappearing by etching at the time of pattern formation (the process of dissolving unnecessary portions of copper foil by the corrosive action of chemicals), a solid pattern should be placed around for protection purposes.

• Required for auto placement and auto insert machine
  
• Placing a fiducial mark on each each side of the board increases accuracy.

6 Part number / Model name

For Identification

Easy to recognize board

Reduce mistakes with similar boards

Additional information such as Serial Number, Revision Number, Lot Number would be useful for identification.

• Printed in legible and in prominent locations