Panel Design of Printed Circuit Boards How to design panels of printed circuit boards that pass through every production process without any problem
Panels for printed circuit board assembly
In highly automated electronics production, machines are used in a so-called inline network. This is most commonly the case in the area of SMT assembly. That means that the machines are arranged as a line one behind the other. Furthermore, they are connected with conveyer belts. The circuit boards to be assembled lie on the conveyer belts and are transported from one production section to the next.
Key data for inline production
- An edge clearance is absolutely necessary for the transport.
- Minimum board size of 50 x 50 mm.
- Maximum board size of 400 x 250 mm (when inserting the board manually, a board size of 508 x 508 mm is possible).
However, deviating dimensions are possible, please contact us!
Panel design for manufacturing and economic reasons
For production and economic reasons, panels are designed which, for instance:
- accommodate non-rectangular printed circuit boards,
- enlarge boards that are too small to the minimum board size for transportation,
- provide greater stability to flex-rigid circuit boards,
- combine assemblies with different boards in one panel,
- integrate many small boards in one panel.
The structure of a panel
A panel consists of one or more printed circuit boards, which are either completely connected or connected to each other via residual bridges.
A distinction is made between scoring or notched panels and milling panels with retaining bridges. Additional holes in the residual bridges facilitate the singulation of the boards later on. A combination of scoring and milling is useful (if feasible) to reduce the milling costs to a minimum.
The position and number of bridges must be carefully determined in relation to the panel or PCB size, component position and PCB thickness in order to ensure both sufficient stability and the singulation of the PCBs from the panel with as little mechanical stress as possible for the solder joint and the component.
If the customer does not specify the geometry and type of a bridge, Kuttig Electronic will realize a bridge.
In order to avoid undesirable errors during panel design, assembly and subsequent singulation, we have compiled some design guidelines below.
Design guidelines for optimal production
For an optimal production of your product we recommend the following key data:
Single board with break-off edge
If components are placed at the outer edge of the PCB, it cannot be transported automatically in the production line. SMD components must therefore have a minimum distance to the outer edge of ≥ 3mm and THT components at least ≥ 5mm. If this cannot be realized, a break-off edge (or panel) must be defined.
Printed circuit boards in scored panels are placed without spacing. All conductor lines and copper areas should have a distance of ≥ 0.5mm to the scoring edge due to the tolerances while singulating the single PCBs.
Please note that the distance between the scored circuit boards should be calculated with 0.0 mm. A distance of 2.0 mm should be planned between the milled circuit boards.
All conductor lines and copper areas should have a distance of ≥ 0.5 mm from the scoring edge and a distance of ≥ 0.2 mm from the milling edge.
Milled panel with positive bridges
With a milled panel with positive bridges, a small overhang remains on the edge of the board after separating the circuit boards. This variant is more favorable in the production of printed circuit boards, but it is not suitable for an accurate installation in a housing in contrast to a milling panel with negative bridges.
Safety distances (blocked areas) for the panel singulator “Hektor” (red areas)
The bridge separator Hektor is a tool for separating mixed multiplier panels. Printed circuit boards are placed in the milling groove over the knife on the die. The bridge is pushed under the punching knife. Then, the bridge is punched out by a foot switch through a compressed air cylinder.
|A||Milling groove width||1,5 - 3 mm|
|B||Cutting length||≥ 6 mm|
|C||Milling groove length||≥ 19 mm|
|D||Component clearance T/B||≥ 22 mm|
|E||Component clearance T/B||≥ 3 mm|
|F||Bridge width||≥ 2,5 - 3 mm|
Milled panel with perforation drilling in residual bridge
If no overhangs are permitted on the circuit boards due to the application, the circuit boards are connected through negative predetermined breaking points.
- All conductor lines and copper areas should have a minimum distance (blocked areas) of ≥ 0.5mm to the outer contour.
- Single boards should always be placed in the panel in one direction. They should not be rotated by 90°, otherwise this can lead to problems in further production process. For instance, SMT wave soldering could create solder bridges because the preferred component alignment is not maintained. (IPC-2221A)
- All single boards should (if possible) be provided with at least four bridges.
Kuttig Standard 1 with a negative predetermined breaking point
|A||Blocked area to the outer contour ≥ 0,5 mm|
|B||Remaining bridge width ~ 0.3 - 0.4 mm|
Kuttig Standard 2 with a negative predetermined breaking point
Mixed multiplier panel
In mixed multiplier panels, different circuit board layouts are combined on one panel. The printed circuit boards are scored or milled.
Please note for panels which should be milled that a distance of ≥ 2.00 mm has to be left between the circuit boards. However, we recommend a distance of 10 mm.
Possible errors in panel designing