PCB Manufacturing

The Ultimate Guide to Finding the Right PCB Assembly Supplier for Your Business

PCB Assembly Services

Finding the right supplier for your business can be tricky. Try a quick search query on the web of potential PCB assembly suppliers in China and you will get a long list of contract manufacturers with various advertisements and promotional campaigns. Supplier selection requires thorough planning and a systematic approach to ensure that all critical aspects are assessed objectively.

At the minimum, a supplier sourcing team should be composed of members from Procurement, design engineering, quality, production engineering and manufacturing teams. This is to ensure a well-rounded decision before coming up with the final PCB assembly partner for your business. The succeeding section provides some guidelines and critical factors to consider when choosing the right PCB assembly supplier.

Cost of PCB Assembly

Practically speaking, cost will always be a significant criterion in any business and in almost all industry types. In PCB assembly, the cost is often comprised of material, assembly, packaging, and other overhead costs. Word of caution: cost is an important, but not the only deciding factor in selecting the right PCB supplier for you. Price is usually negotiable, and it should not be at the expense of the quality of the boards. For instance, to cut down the cost of the PCB, your supplier offered a lower assembly price in exchange for removing sampling inspection controls in some of the processes. You must carefully study the quotation and you must ensure that the terms and conditions are specific, with a complete and detailed breakdown. Any vague term should be clarified with the supplier at the early stage of the discussion to avoid misunderstanding that may incur additional costs.

PCB Assembly Quality Controls

Quality Controls

Quality is often written in big bold letters on banners if you happen to walk inside a manufacturing floor or even if you visit a PCB assembly webpage. This is done to attract customers and to inculcate a Quality mindset and culture among the employees and personnel. Quality means that the assembled PCB conforms, not only to known international standards, but also to customer requirements and internal specifications.
Equivalently, compliance to standards means implementing quality controls in every process during PCB assembly.

Customer feedbacks and high-cost reworks and recalls can be prevented if the quality of PCB is guaranteed. A documented control plan should be available, detailing the frequency and method of quality checks like first article and in-process inspections. A set-up checklist will also ensure that the machines are in good condition and that product buy-off is performed prior to running high volume. Any out-of-control or quality deviations should have corresponding reactions and corrective plans. This is to ensure that any problems encountered during processing are well-analyzed and improvement actions are being implemented.

Most electronics manufacturing service providers employ Lean Six Sigma methodology and PDCA (Plan-Do-Check-Act) as a tool for continuous improvement and defect elimination. The engineering team should have improvement plans to optimize the process and reduce occurrences of defects.

Technical Capability

PCB assembly is composed of highly specialized and technical processes that require high-speed automatic machines. Each PCB assembly supplier offers machines and services with different capability. Below are the generic machines involved in PCBA (Printed Circuit Board Assembly):

  • Solder paste printer
  • Component Placement machines
  • Automated Optical Inspection
  • X-ray machine
  • Reflow oven

Nowadays, PCB designs are becoming more intricate, thus you should know each of the equipment’s tolerances and offset. For example, solder printing and component placement machines should have minimal offsets since major movements or drifts of the components and solder paste may cause alignment and test issues in the PCB.

The right PCB assembly supplier should be able to understand and interpret your requirements and give assessments if the PCB is manufacturable. You must also check the supplier’s other technical capability like reliability testing and in-house failure analysis capability. If possible, the PCB assembly supplier should have a similar or comparable existing project. You may ask for the historical yield performance, top defects, and customer complaints for their existing projects.

Years of Experience

Knowing your suppliers’ years of experience in PCB assembly gives you the confidence that they have been making the product and providing the service repeatedly over a certain period. A justified track record in terms of number of shipped PCB, engineering experience, yield trend and field failures should be presented. You should know the supplier’s innovative ways to grow and improve their assembly processes. Some suppliers have been in service for a long time, but the machines are already outdated with limited capability. You must be able to know the supplier’s innovative programs to improve their assembly processes and quality controls.

PCB Assembly SMT Assembly

Compliance to Standards

Standards are documented guidelines and requirements internationally recognized in the electronics manufacturing industry. Without these standards, PCB suppliers will define their own criteria and procedures, relaxing or tightening them without referring to any known rules and guidelines. Consequently, same board will be produced differently, and the quality of the PCB will be at risk putting the customers and PCB users in jeopardy.

You must investigate the compliance of the suppliers to IPC (Institute of Electronics Circuit Packaging) standards, which is involved in the generation of important standards related to design guidelines, test methods and industry issues. A reputable PCB assembly supplier should have IPC-A-610 as reference standards for PCB acceptability and quality criteria. IPC have specifications for the entire aspects and lifecycle of PCB like design, data exchange, assembly and testing.

Since PCBs are at the core of electronic devices, safety is very important. Flammability testing, environmental testing and electrical testing are some of the analytical techniques that the PCB goes through to ensure its safety, quality and reliability. Underwriters Laboratories or UL is a known certifying body which have defined safety standards. The other components and subassemblies should also be certified by UL to increase the credibility of the product.

Note, however, that IPC, ISO, UL and other standards should be the baseline and minimum requirement, which means that stringent measures can further be implemented by the supplier like tighter tolerances.

Cycle Time

PCB assembly supplier will typically provide a standard lead time for the completion of the boards. The right PCB assembly supplier can provide fast turnaround times and can support expedite options for your business. Part of the assessment is how the supplier manages the inventory and safety stock to mitigate late deliveries and meet the minimum order quantity.

Ideally, the PCB supplier should both have a prototype facility and a high-volume manufacturing facility for easier communication, but depending on your business strategy, you may opt for different supplier for prototyping and production PCB especially if you are trying to drive for lower cost. Note, however that the overall cycle time will be relatively longer if the PCB fabrication and assembly sites are not collocated.


Bear in mind that the supplier you choose will be your business partner whom you’ll have frequent communications with, whether it be about shipment, improvements, sudden changes, and issues. Open and honest communication between customer and supplier is important to ensure that all requests and relayed information are well-understood. Responsiveness of the supplier also means having constant updates to achieve on-time delivery and lead time agreements for orders and design modifications.

The hard truth is a perfect PCB assembly supplier does not exist. Each supplier possesses strengths and weaknesses that you need to scrutinize at the planning stage of your project. With the dynamic scene in the electronics manufacturing industry, various supply chain issues, rapid technological advancements and policy changes are unavoidable. You must gauge the relative weight of each factor mentioned above to finalize the overall performance of the supplier.

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