For printed circuit board assembly, it helps to have an array of manufacturing capabilities, the latest assembly technology, and cutting edge inspection and validation processes.
Surface mount technology (SMT) describes the method used to mount electronics on the surface of a printed circuit board. One of the smallest is the 01005 assembly. This number refers to the size of the 01005 components, which are from 0.2mm to 0.4mm. Their size and weight (on average 0.4g) must be considered in the assembly process. Component placement must be no less than 150µm and up to 250µm. Too large a gap in the solder mask opening will leave components vulnerable to shifting and the end product vulnerable to intermittent failures.
Printed circuit board (PCB) layouts for chip-scale packages often use microBGA placement at 0.4mm pitch. This is a micro-ball array used for electronic circuit assembly. MicroBGAs are spaced only 0.1 to 0.8mm apart, which helps conserve space.
Manufacturers often use mixed technology to create circuit boards, performing SMT first and then through-hole technology to run the leads.
Through hole technology uses predrilled holes on PCBs to ensure proper placement and alignment of leads on components. In some companies this is still done by hand, although the majority of manufacturers rely on automated insertion mounting machines on high speed automated lines.
During assembly, components are scanned via an automated optical inspection device for surface flaws, inconsistent soldering, and out-of-place or missing components. Ball grid array components (BGA) often require 3D x-ray validation to get a clearer picture of structural defects and shielded parts.
BGA circuit boards, which allow more surface area to be used for mounting microprocessors, are still popular, but are being joined by more environmentally friendly methods. One of these is the land-grid array (LGA) which is similar to a BGA but has no spheres. LGA solder interconnections are formed only by the solder paste, and thus reduce the amount of hazardous substances used.
While many manufacturers and industries are phasing out the use of lead, leaded processes, such as QFN (quad flat no leads,) and µBGA are still being used and provide several advantages over lead-free processes. These include less self-inductance, lower resistance levels and less impedance discontinuity.
Lead free assembly processes present other challenges, particularly with increased temperatures during soldering. Because of this there is also a reduced thermal processing window. The change from leaded to lead-free is inevitable however, and is happening worldwide.
BGA assembly is not obsolete, though, and the practice of POP (package on package) assembly is proof of this. POP is simply stacking components on top of each other, which allows for enhanced functionality in the space of a single BGA.
Advances in printed circuit board assembly include rigid-flex and flex assemblies, which combine the flexibility of copper circuits with the rigidity of PCB circuitry to create an ideal solution for larger storage devices. Manufacturers even have machines configured to handle large PCBs up to 24″ x 26″. In addition, advanced material requirements planning (MRP) systems help manufacturers control costs and keep quality consistent. By increasing component and board traceability, production control is assured.
While these processes represent the latest PCB assembly technology, it is likely that newer, more efficient and less toxic processes will soon replace them.
Whether you need printed circuit boards repaired, tested, designed, built or assembled, the team at MJS Designs is ready to help you get your product to your consumers on time and on budget. Visit us online at www.mjsdesigns.com or like us on Facebook for the latest updates and information.