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by NextPCB
Electronics manufacturing can be a daunting yet fascinating field. The penetration of electronics in every aspect of life - from complex circuit boards in everyday devices to sophisticated PCB assembly processes - is a testament to the technological advancements made over the past half-century, which have only recently become more accessible to non-experts.
In the past decade, the industry has transformed with new players like NextPCB in Asia offering highly competitive and affordable quickturn manufacturing services and one-stop-shop solutions to international markets, removing major obstacles for hobbyist circles and small-scale businesses while providing more flexibility compared to their traditional counterparts.
This rapid globalization of electronics manufacturing has enabled the emergence of new techniques and approaches and opened doors to new customers who need to get up to speed quickly in the highly competitive electronics market.
There is no shortage of resources available but bite-sized chunks of information from disparate sources of varying quality and age can lead to conflicting information and a fragmented understanding. This guide aims to make sense of it all by bringing you up to date with common PCB assembly services terminology, PCB basics and PCB assembly processes that go into producing electronic hardware and the considerations that go into making cost-effective,producible and reliable electronics in today’s fast-paced industry.
Printed Circuit Board Assembly, sometimes abbreviated to PCBA, describes the process of populating the bare circuit board with electronic components, including the formation of solder joints and subsequent testing and inspection procedures. The abbreviation PCBA can also describe the populated device, i.e. PCB assembled. So 5 PCBA would be 5 assembled PCB devices. PCBA also typically refers to the populated circuit board without the enclosure or mechanical parts.Understanding pcb assembly meaning is essential for distinguishing between bare PCBs and fully assembled boards in manufacturing workflows.
Bare PCB on the left and populated PCB with components on the right
PCBA devices and processes can be labeled according to how the boards are to be assembled, the number of sides, and the types of parts to be populated onto the board etc. These labels can indicate to manufacturers how assembly should be approached and can have significant influence on cost and production difficulty, which in turn influences design decisions.
This refers to the types of components destined to be soldered onto the boards. As the name suggests, through-hole parts have long leads that go through the boards through plated through-holes (PTH). Molten solder is then applied to the opposite side or both sides to hold the part in place.
Surface mount components have metallic contacts that are attached to solder pads situated on the surface of the boards.
A circuit board that only has through-hole devices (THD) or surface mount devices (SMD) can be called a through-hole board or surface mount board, respectively.
Nowadays, most devices have a combination of both types of components to make the most of their advantages. Such boards are referred to as mixed assembly boards.This integration of technologies is a key part of the modern printed circuit board components assembly process.
The following acronyms are often used to label processes, parts and designs:
Single and double-sided refers to the number of assembly sides required to complete a PCBA. A single-sided PCBA is a design where components are only located on one side whereas for double-sided PCBA, components are soldered to both top and bottom sides. For both surface mount and through-hole boards, double-sided assembly increases production complexity.
For example, double-sided surface mount boards that undergo soldering in a reflow oven require two passes, one for each side. Often, the side with fewer or lighter components are populated first, then the boards are flipped over and the process is repeated. This helps prevent heavier parts from detaching during the second pass. Custom trays and/or glue may also be used to hold heavier parts in place, being critical in the overall pcb assembly process to ensure consistent quality across both sides of the board.
This refers to how the boards are assembled and has a strong influence on the cost-benefit ratio. PCBA boards can be manually assembled, assembled using automated machines, or by using a combination of manual and automated methods, each of which has its advantages and disadvantages.
Manual Assembly
Manually assembled or hand-soldered boards are soldered using non-automated means. For through-hole parts and (surface mount parts to some extent), this involves a technician using a soldering iron and coils of solder wire. For surface mount assembly this could mean manual stencil printing and placement of parts before being placed into a reflow oven.
Manual assembly can be beneficial for prototype orders where only a handful of pieces are required. Automated equipment often requires setup or programming that is specific to the design which may not be worthwhile for small orders.
Automated Assembly
Automated assembly in a mass production setting uses a fully connected online assembly line where machines are connected head-to-toe and boards pass on conveyors from one machine to the next. This sophisticated pcb assembly line set-up requires minimum supervision and can be left running over long periods, but set-up and ironing out problems take up a substantial amount of time and resources. Small batch or agile operations can be semi-automated to facilitate flexibility, which is necessary to cater to a high volume of small orders.
Automated assembly of through-hole parts could involve an automated insertion machine before passing through a wave soldering machine. Surface mount parts can be placed on PCB boards at high speed and accuracy with the help of pick-and-place machines.
Advantages and disadvantages of manual and automated assembly methods
Contract manufacturers often offer complete turnkey manufacturing solutions to their clients. Turnkey PCBA involves taking the client’s design documentation and taking care of the procurement of all materials and manufacturing, including the manufacture of the bare PCBs. Turnkey service providers often also provide other EMS (Electronic Manufacturing Services) such as electromechanical assembly and firmware burning.
The words turnkey or consignment refer to the procurement of electronic components and bare circuit boards. For consignment projects, t
