specialized pcb manufacturing process steps

PCB Manufacturing Techniques from Start to Finish

PCB manufacturing techniques are diverse processes that transform the laminates and other materials into the finished PCBA consumers are familiar with. For those less familiar with the final product, the PCBA represents the unified components and substrate most conducive to the circuit application and environment. Several stages are necessary to round the board materials and sub-products into their final form.

Fabrication

Artwork, Stackup, and Drilling

• Technicians cut board materials into working panel sizes (remember: board costs operate on a per-panel basis – arrangement on the panel to maximize board output improves cost-effectiveness).
• Photosensitive dry film and UV exposure transfer the artwork to the board surface.
• Etchant solutions remove the uncovered portions of the copper-clad laminate, resulting in a circuit corresponding 1:1 to the artwork.
• The etched circuit leverages an automatic optical inspection (AOI) that compares the physical copper features against the artwork data.
• Operators repeat each board layer’s artwork transfer, etching, and AOI process. Once complete, a high-temperature press fuses the individual board layer materials to form the completed layer stackup.
• Manufacturers drill non-plated holes into the stackup according to the drill chart. For regular-sized holes, only a mechanical drill is necessary. However, smaller holes may require laser drilling. Microvias, a much smaller drilled hole for high-density interconnect (HDI) designs, require repeat lamination-to-drill steps before a final lamination, as overly deep microvias encounter reliability issues.

Ready To

Get Started?

• Manufacturers use a hybrid electroless and panel plating to form a uniform deposition of copper on the surface of the plated hole walls. The electroless plating is thin and acts as a substrate for the subsequent panel plating process, as the former can deposit metal on non-metal surfaces. The combined plating methods provide an exact yet robust amount of copper to minimize reliability issues such as intermittent connectivity, high impedance, or, in catastrophic cases, barrel cracking.
• The outer artwork etching begins with the inner layer artwork complete, the layers laminated in the stackup, and the holes drilled/plated. As with the inner layers, AOI compares the physical copper to the digital artwork to determine the correctness of the etch process.
• When the fabrication notes call for filled/plugged vias, the manufacturer will use a laser-cut stencil to allow for solder mask (or some other nonconductive fill material) inflow into the vias.
• Technicians once more utilize the outer layer artwork to determine solder mask coverage. Openings in the solder mask are necessary for assembly (components cannot solder down without an opening in the stencil); however, the solder mask helps prevent bridging between pads during automatic or manual solder application steps.
• Manufacturers apply a surface finish to the exposed copper for increased longevity and promote solderability during assembly.
• A router helps fully or partially separate individual boards from the panel.
• Electrical testing confirms continuity throughout the nets as specified in the netlist; if any unintentional shorts or opens are present, the test notifies the operator.
• Optical inspection – including automatic visual inspection (AVI) and automatic x-ray inspection (AXI) – confirms the quality of the manufacturing processes by detecting or failing to detect common defects.

Assembly

• Component selection according to package, assembly integration style, and other important manufacturing and performance characteristics occur much earlier during the board design phase. Many components can be surface-mount device (SMD) or through-hole (TH). Each has advantages and disadvantages, with SMD trumping in terms of footprint real estate and cost, while TH is more suited to prototyping.
• Note that designers don’t have to be fully SMD or TH assembly; some components may only have one package available. Designers can mix and match the packages to optimize availability, component cost, footprint size/layout, and procurement lead times.
• Using a stencil, technicians apply a thin coating of a solder-mask-and-flux mixture that holds components in place before soldering.
• An automated placement machine known as a pick-and-place rapidly places components according to the component XY data generated during manufacturing file output. SMD components are most suitable for automated placement; some larger components may require manual placement/soldering.
• Manufacturers employ a wave solder machine or a reflow oven for automated assembly of TH and SMD components. Regarding quality, cost, and throughput, designers can save on all three by constraining components to a single side of the board, using only one component integration method (SMD/TH), or isolating SMD/TH placement to opposite sides of the board.
• According to the schematic, functional testing confirms the circuit does what it intends to do. It checks and measures the electrical characteristics of the PCBA by passing simulated signals through the circuitry.
• Final board inspections using manual inspection, AVI, AXI, and AOI techniques catch any defects related to the assembly process.

Your Contract Manufacturer Ensures Quality and Reliability

PCB manufacturing techniques cover the many disparate processes required to fabricate and assemble a finished PCBA and the optimal procedure for ensuring quality and reliability while minimizing defects. The best-manufactured boards come from designs that are mindful of the restrictions and precision of fabrication/assembly equipment. If you’re unsure if your design is optimal for a manufacturing run, VSE is here to help. We’re a team of engineers committed to building electronics for our customers, including a thorough design review for manufacturability. We’ve been realizing life-changing and life-saving designs for over forty years with our valued manufacturing partners.

If you are looking for a CM that prides itself on its care and attention to detail to ensure that each PCB assembly is built to the highest standards, look no further than VSE. Contact us today to learn more about partnering with us for your next project.