Designing three-dimensional circuitry bodies (MIDs)
Considering some design rules and requirements makes the successful realization of MIDs simple. Some parameters are described on the following pages:
Line and Space |
 |
| One of the important goals during the development and manufacture of 3-dimensional circuitry is the efficient use of space with the finest possible structures. Track widths of ≥150 µm and gaps of ≥200 µm have proven ideal in practice, although thinner tracks and gaps are possible. |
Size of workpiece |
| The zone in which the component can be processed is limited by the maximum possible scan field volume of the laser. The scan field of the LPKF MicroLine 3D laser system for instance has a frustrum with a base diameter of 160 mm, a height of 24 mm and a lateral area angle of inclination to the base of 77°. |
Angle of Attack |
The surface of the polymer is activated by the laser light. The maximum angle of incidence of the laser beam on the surface to be structured must not be exceeded if safe activation is to be achieved.
The angle of incidence is the angle between the orthogonal to the activated surface and the laser beam. Angles of incidence exceeding 70° are reduced by rotating the component during the laser processing step. This technique can also be used to realize artwork lying on surfaces separated by angles of 90°. |
Walls and Ejection Pins |
|
Zones to be subsequently activated should not touch walls directly. The separation for walls with an angle of 45° should be ≥150 µm, the separation from steeper walls with angles of 70° for instance should be ≥250 µm. An adequate separation between the tracks and ejection pins must also be incorporated in the design. |
| |
Optimum cycle times
The cycle time of each component also has to be minimised to ensure cost efficiency of the laser structuring side of the LPKF-LDS™ method. This is mainly determined by the handling time and the structuring time, which is also proportional to the layout area. The handling time is mainly determined by the number of positions into which the component has to be placed. The number of positions and the layout area should be reduced to a minimum by appropriate component design. |
Activating through-holes |
To ensure that the laser can process the inside walls of the through-plated hole at a suitable angle of incidence, the vias have to be conical on one side or both sides depending on the thickness of the material. In the case of thick walls, the internal diameters of the vias must be enlarged to ensure unimpeded processing by the laser beam (aspect ratio of simple cones 1:1; for double cones 2:1). |
Fixtures, clamps and bonding seams
The components have to be fixed in place during laser structuring and assembly. The fixing positions must not harm any sensitive parts such as tracks, contact pads or component seats. Tracks must not be laid over bonding seams of the thermoplastic part.
|
