Printed circuit boards (PCBs for short) are the primary component in the majority of electronic devices and appliances. Pretty much anything that has an on/off switch will feature a PCB. In this blog, we will guide you through the steps involved in printed circuit board production, turning a PCB into a PCBA (printed circuit board assembly).
Camtronics doesn’t offer a design service, so this stage is handled by our customers. Once a design is released, the designer will provide a package of data to allow Camtronics to translate the engineer’s work into physical reality.
This data will include, as a minimum, gerber files, PCB specification, and a bill of materials, or BOM. Most will also provide ‘pick-and-place’ data – a file which stipulates the centre point and rotation of each part on the assembly.
The gerbers and PCB specification define the bare board’s size, shape, thickness and pad locations. The BOM tells us what parts are required to assemble the product, and the pick & place data tells us where to put them.
With this data in place, we can get on with the business of PCB assembly.
For the purposes of this blog, we’ll assume all the material is on-hand and that the assembly features surface mount devices.
The most important part of the SMT process. A stainless-steel screen, with a thickness and apertures depending on the component technology on the PCBA, is offered up to the PCB using automated vision alignment of fiducial marks on both items to ensure a precise print. A squeegee then draws a bead of solder paste across the stencil which forces solder paste through the holes and deposits the paste on the PCB pads. The board ‘snaps’ away from the stencil, leaving neat blocks of solder paste in the required locations, and is passed via conveyor to the next stage of the process.
This is the ‘easy’ bit. Parts are placed on the PCB in accordance with the BOM and pick-and-place data, which are combined to generate a machine placement program, at a rate of around 20,000 components per hour with 50-micron accuracy. Devices, which are presented to the machine on trolleys of tubes or reeled tapes, can be as small as 01005 chips, which measure 0.4mm x 0.2mm.
Running a close 2nd to screen printing in the importance stakes, reflow is the stage where the solder paste is melted to physically solder the placed components to the PCB. For each PCBA we make, a bespoke reflow ‘profile’ is generated using a KIC Technology profiler. This matches the thermal demands of the circuit to the heat we apply, ensuring all components are correctly soldered without suffering thermal shock or excess peak temperatures. During this process, the flux in the solder paste is activated to clean the metal surfaces before the paste moves to its liquidous state at the higher temperatures, to create what you’d recognise as solder joints.
Surface-mount assemblies are inspected using an Automated Optical Inspection (AOI) which inspects the solder joints and components on the PCB. Hundreds of inspections per minute are conducted on each PCBA. These include component identification, placement accuracy, orientation and solder fillet inspection using an RGB lighting system.
Any PCBs not conforming to IPC acceptability standards are identified and segregated. If rework is required, the rework technician is able to access the defect details by scanning the barcode fitted to each PCBA.
Inspection is an important part of the printed circuit board production process. In addition to AOI, we maintain a complementary manual inspection stage for a more subjective overview of a circuit, such as looking at the solder finish and general aesthetics of the PCBA.
Our experienced team of inspectors at Camtronics carry out PCBA inspections and visual checks to IPC-610 standards.
Following SMT assembly and inspection, PCBAs are passed to the Conventional Assembly process for the addition on pin-through-hole (PTH) parts, if required. These parts can be soldered by hand, or by wave soldering if appropriate. After a further inspection stage, PCBAs can move to functional test, mechanical assembly (also known as box build), conformal coating or despatch, depending on customer requirements.
We are experts in high-quality printed circuit board production. Our experienced purchasing team can source PCB materials and from across the globe to provide you with the optimal solution to your requirements.
With Camtronics as your manufacturing partner, you can concentrate on your business and leave the PCB assembly to ISO9001 certified experts. Contact us online or over the phone to see how we can help.
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