Figure 1: PCB Milling Machine - S103 by LPKF (via LPKF USA)
TEAM Lab Equipment and Techniques: Printed Circuit Board (PCB) Manufacturing
Basic Overview of PCB Manufacturing Equipment: PCB Mill:
Our PCB micro-mill is capable of producing dual-layer custom circuit boards using materials such as FR-4 and other circuit board materials. Typically, we limit activities to providing a bare (copper) board. Generally speaking, our services are most applicable in cases where a basic prototype is required quickly, and/or your needs are very simple (1-2 layers, no solder resist, only a few vias); other board-manufacturing services (oshpark, seeed studio, etc) are capable of making far more complete, and feature-rich boards at low-cost. In some cases, we also offer basic PCB design services.
In Depth Overview of PCB Manufacturing Equipment: PCB Mill:
Very precise CNC Mill specifically designed to manufacture Printed circuit boards by way of copper-layer removal. The machine uses an array (qty = 15 simultaneous) tools to drill holes, mill insulating paths into coper, and route the perimeter of the board from bulk-stock. Resultant PBS are typically 2 layered (front and back) bare copper without thru-hole plating. Vias need to be added post-process, by way of copper rivet, or scrap wire soldered on both sides of the board.
Upon completion of PCB manufacturing phase, Soldering equipment is used to manually mount circuit elements. Alternative (or in addition) to this, more automated processes may be available by pick-andplace. This equipment is available for use by students within the lab.
Figure 2: Soldering Station for Thru-Hole Circuit Elements, and (some) Large SMD devices
In cases where boards are designed with SMD (Surface Mount Device) components, Automatic pick-and place machine use may be an option for automatic assembly. Please consult with the TEAM lab manager for details.
Also for SMD devices, the TEAM lab has a programmable reflow oven designed for reflow soldering of SMD components. Consult with the TEAM lab manager for details.
Typically, circuit boards are broken into two categories: Flexible, and Rigid.
Rigid circuit boards manufactured within the TEAM lab are typically manufactured from “Copper-CladFR4,” which is a glass-reinforced epoxy laminate sheet clad with a thin layer of conductive copper on one, or both sides. From this, the PCB mill cuts away insulating paths to create conductive traces on the board.
Figure 3: Copper Clad FR4 - Insulating fiber at center, Copper on one or more sides
Figure 4: Copper Clad FR4 Being Milled into Functional PCBs
Occasionally, a flexible circuit may be required, or favored over a rigid one. Our printed circuit board milling machine is also capable of manufacturing these circuits, with patience. These circuits are typically composed of a central layer of kapton film, clad with copper on the top and bottom. As with rigid boards, copper is milled away to isolate patches from one another, and generate traces. Additional layers of kapton can be used to mask exposed coper after machining.
Figure 5: A Flexible Printed Circuit
Circuit development is a long process that begins with concept, transitions into bread-board testing, and concludes with development and manufacturing of a circuit board. Be prepared to create multiple revisions, as this is common to PCB development. Also be sure to sufficiently test your circuit before committing to a printed circuit board to minimize troubleshooting.
Figure 6: Breadboards are Often Used to Test a Circuit before Manufacturing a PCB
While professional PCB designers typically make use of software packages like Eagle CAD (by Autodesk), there are numerous other packages that are (by design) simpler, and easier to use. Further, many of these entry-level packages also work with Arduino to digitally test circuits within software (before generating a physical prototype).
Eagle CAD: Professional grade CAD software, free version with limited board footprint available
Tinkercad Circuits: Web-based drag-and-drop circuit design with Arduino integration. For basic designs only.
Fritzing: Easy drag-and-drop circuit design. For basic designs only.
Preparing Files for the PCB Mill
The PCB mill requires “Gerber” Format files – One file per layer of the printed circuit board. Please supply these files, as well as the original design file when submitting a board for manufacturing. If using Eagle, please contact the TEAM lab manager for the “job processor” that automatically exports the proper layers.
Board assembly typically consists of manual soldering for thru-hole elements, and reflow soldering (by way of programmable reflow oven) for SMD elements. Computer-guided pick-and-place should (most often) be used in cases of close-pitch SMD circuit elements. Contact the TEAM lab manager for more details.
Figure 7: A bare Copper Printed Circuit Board
Sources and Resources:
Tinkercad Circuits: https://www.tinkercad.com/
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