Answering the question “How long does it take to assemble a PCB?” requires a comprehensive understanding of the assembly process, materials involved and potential delays. Procurement managers, designers and engineers must assess these factors. Choosing an experienced contract electronics manufacturer (CEM) significantly impacts speed, efficiency and quality of Printed Circuit Board (PCB) assembly.
This blog will delve into assembly processes, materials, potential delaying factors and insights into selecting a trusted CEM, summarising the time and resources needed for efficient and cost-effective PCB assembly.
What are the typical processes involved in the manufacture of PCB assemblies?
PCB assembly involves several critical steps to ensure the correct placement and functioning of electronic components on the board. Here’s an overview of the typical processes involved in PCB assembly:
Step 1: Solder paste stencilling
Solder paste stencilling involves applying a stencil over a bare PCB. Solder paste, a mixture of tiny solder balls and ‘flux’ (a chemical cleaning agent) is spread across the stencil using a squeegee. The paste fills the openings in the stencil and adheres to the PCB. The stencil is then removed, leaving solder deposits ready for component placement.
Step 2: Pick and place
Automated pick and place machines are used to place electronic components on to the surface of the PCB to ensure precise and accurate placement.
Step 3: Surface mount soldering or Reflow soldering
The PCB is heated in a ‘reflow oven’ to melt the solder paste, which then solidifies to create electrical and mechanical connections in order to permanently and securely attach the components to the PCB.
Step 4: Quality control
The PCB is inspected using automated optical inspection (AOI), X-ray inspection or manual inspection to detect and correct any defects such as solder bridges, misaligned components or other errors.
Step 5: Through-hole component insertion
Some PCB designs may also require plated through-hole assembly, in order to pass electrical signals from one side of the board to the other. In this step, through-hole components are manually inserted into pre-drilled holes on the PCB and are soldered into place by hand.
Step 6: Wave soldering
After inserting the plated through-hole components, the PCB is passed through another oven wherein the bottom of the board passes over a ‘wave’ of molten solder to simultaneously solder the components in a fast and efficient manner. Some components are sensitive to the high temperatures of wave soldering or are not suitable for automated processes. Manual soldering allows for better control of heat and handling.
Step 7: End inspection and testing
The CEM will perform functional testing, in-circuit testing (ICT) and other quality control tests to verify that the assembled PCB works correctly and meets all specifications.
Step 8: Conformal coating
In this step, a protective coating is applied to the PCB to protect it from moisture, dust, chemicals and extreme temperatures.
Step 9: Complete assembly
The PCB is assembled into its final product enclosure or housing.
Step 10: Packaging and shipping
The PCBAs are packaged to ensure safe transportation and delivery to the customer or next stage in the supply chain.
How do CEMs ensure PCBs are assembled efficiently and cost effectively?
Assembling PCBs is a multi-step process and CEMs employ a number of ways to make it more efficient and cost effective:
- Automation – by investing in the latest technology, such as automated pick and place machines, to speed up the assembly process and reduce human error.
- Automated Optical Inspection (AOI) – used to detect defects in the assembly process, enabling CEMs to address any rework requirements early on, reducing overall cost and time needed for corrections.
- Collaboration – through working closely with the PCB assembly designers, CEMs can advise on producing PCB assembly layouts that are easier and cheaper to manufacture.
- Ongoing training – providing learning and development opportunities for staff builds a skilled workforce, ensuring the efficiency of the PCB assembly process, as well as the quality of the final product.
Find out more about MPE’s PCB assembly processes
by contacting our Sales Director, Paul Carter here
Which materials are required?
PCB assembly involves a variety of materials, each playing a critical role in ensuring the functionality and reliability of the final product.
- PCB substrate materials – the materials required to make the bare boards
- Copper – the primary material used for conductive traces and pads on the PCB
- Solder paste – a mixture of tiny solder balls (usually a tin-lead alloy or lead-free alloys such as tin-silver-copper) suspended in flux.
- Surface mount components and through-hole components
- Solder wire and masks
- Stencils
- Adhesives
- Cleaning agents
- Conformal coatings
Bill Of Materials to streamline assembly
CEMs, in conjunction with designers, purchasing staff and engineers, will typically generate a ‘Bill Of Materials’ (BOM), a detailed list of all the materials and components required to assemble the PCB. The BOM includes detailed information about each item, such as part numbers, descriptions, quantities and specifications.
This document ensures the assembly process runs smoothly by reducing the risk of purchasing incorrect or incompatible materials, ensures all components are in stock, facilitates bulk purchasing for better pricing deals, reduces rework and wastage overall, as well as supporting the testing and inspection process, as well as quality control, by providing traceability.
Accurate Inventory control
Maintaining an accurate inventory of frequently used resistors and capacitors enables CEMs to ensure ‘buffer stocks’ are ready for use. MPE collaborates and buys directly from approved distributors and suppliers locally where possible to reduce risks, such as delayed delivery or counterfeit components and materials. This ensures we keep to the agreed production schedule and can guarantee the quality of the final assembly.
Factors contributing to potential delays
Several factors can contribute to delays in the PCB assembly process, impacting project timelines and delivery schedules, such as:
- Component availability
- Supplier issues, including shipping delays, quality problems and sudden price changes
- Design changes
- Equipment malfunctions
- Process bottlenecks owing to resource issues and/or inadequate training
- Quality issues
- Environmental factors, such as power cuts
- Lack of communication and coordination
Avoiding delays to your production schedule
Finding a reliable and experienced CEM to assemble your PCB is essential when it comes to keeping to schedule and ensuring the quality of your end product.
Posing the following questions to your prospective CEM will help you identify your ideal manufacturing partner:
- How do you ensure timely availability of components, especially those with long lead times or limited availability?
- How do you mitigate risks associated with supplier-related issues such as shipping delays, quality problems or sudden price changes?
- What steps do you take to optimise production processes and minimise bottlenecks that could lead to delays?
- What measures do you have in place to maintain high-quality standards and prevent defects that could cause production delays?
- How do you ensure the reliability and uptime of your manufacturing equipment to prevent delays due to breakdowns or malfunctions?
- How do you keep clients informed about the status of their projects and any potential delays that may arise?
- What contingency plans do you have in place to address unexpected events or emergencies that could impact production schedules?
- How do you ensure that resources such as manpower, materials and equipment are effectively allocated to prevent bottlenecks and delays?
- What steps do you take to continuously improve your processes and address any recurring issues that may lead to delays?
Find out more about how MPE assembles PCBs efficiently and cost effecting
by consulting our FAQs here
So, how long does it take to assemble a PCB?
The assembly time for a PCB varies based on factors like design complexity, materials required, and assembly method. Prototypes or small batches may take hours to days, while larger-scale production can be significantly faster with automated processes, typically ranging from a few hours to a few days. When it comes to assembly, partnering with a reliable CEM is vital to keeping to schedule. Evaluating their processes, materials handling as well as experience in PCB assembly will enable you to secure timely completion and the superior-quality of your assembly.
MPE Electronics is an established and experienced contract electronics manufacturer specialising in PCB assemblies and full box build assembly for a wide range of commercial and industrial businesses.
To find out how MPE Electronics’ PCB manufacturing and assembly services can benefit your business, contact our expert and friendly team on +44 (0)1825 764822 or enquiries@mpe-electronics.co.uk.
