how to order pcb assembly

FAQ: How to Order PCB Assemblies

It is hard to imagine a time when a company’s clientele was limited to customers who resided in the same town. Fortunately, pioneers like Hammacher Schlemmer—and later Montgomery Ward and Sears, Roebuck and Company—remedied this situation by offering mail-order in the mid to late 1800s. Mail order continues today; however, it has been eclipsed by an even faster and more convenient method of ordering products: online shopping.

The internet’s impact on the ability of business and service providers to connect with and sell to customers is nothing short of revolutionary. And contract manufacturers (CMs) that build electronic circuit boards take full advantage of the web for B2B and B2C commerce. Although the internet has become our common communication medium, several important FAQs about how to order PCB assembly services must be considered to ensure your board build meets your requirements.

What are the different ways to order PCB assemblies?

There are three types of PCB manufacturing services that include assembly:

PCB Assembly Order Options

  • Assembly Only

For this service, the board designer provides fabricated boards and components to be assembled by the CM.

  • Fabrication and Assembly

The CM performs all of the board construction for this service; however, the company that designs the PCBA must provide the components.

  • Turnkey Manufacturing

This is the most comprehensive and fastest service, where the CM is responsible for fabrication, component procurement and assembly.

If furnishing the components, how should they be packaged?

Today, CMs use automated pick-and-place machines and other specialized PCB assembly equipment to ensure the precise placement of components and the achievement of good solder joint quality. Depending upon the CM’s machine(s), components can be loaded from reels, tubes or trays—sometimes called flat packs. You should consult with your CM to ensure that components are ordered and delivered in a package that their equipment can utilize.

Can I specify how the components are soldered for my PCB assembly?

The engineer or PCBA designer has almost complete authority to specify how boards should be built; although, to ensure the most efficient and highest-quality board build process, a good design development checklist should guide your decisions. This includes collaboration with and usually deferment to the CM’s discretion and industry standards. The soldering process—wave, selective or another method—typically lies with the CM and is determined by equipment, capabilities and the type of components attached. For example, wave soldering and selective soldering are often used for through-hole technology, while reflow is used for SMDs.

Are there any design rules and guidelines that are important to follow for PCB assembly, as they are for fabrication?

Yes. It is important to follow your CM’s DFM specifications for all board manufacturing projects. For turnkey manufacturers, these will include design for assembly (DFA) rules, as well. Design rules include directives for pad and trace alignment, board element spacing and clearance limitations, thermal dissipation and distribution, edge clearance and depanelization, staking and/or underfill clearances, top and bottom component package groupings, component specifications versus intended wash process rules and other decisions that impact the assembly process.

For turnkey manufacturing services, is it better if my CM performs PCB assembly or fabrication in-house?

As a recent State of PCBA Manufacturing survey indicates, most developers like to work with the least number of EMS providers possible, which means that turnkey services are preferred. When choosing a CM, there are distinct advantages to working with a CM that does assembly in-house that impact the turnkey manufacturing process quality. For instance, in-house assembly ensures that final board inspection, cleaning and packaging responsibilities reside with the assembler.

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What is the best design package format to use when ordering a PCB assembly?

For many decades, Gerber files have been the de facto standard for PCBA design files. However, data-rich design files are gaining popularity and are preferred by organizations such as IPC, the PCB industry leader in defining regulations and standards for all aspects of board development.

Is the BOM part of the design package?

The manufacturing file(s) sent to your CM should contain all the information, data and imagery needed to build your boards to accurately reflect your design and its intent. And an essential part of the package is the BOM. The accuracy of this electronic component list is critical for PCB assembly.

How do I order PCB assembly changes?

During prototyping—the most important stage of PCBA development—making and instituting changes that impact assembly are not anomalies; they are commonplace. The process for making modifications that impact manufacturing often begins with an engineering change order (ECO). Some PCB design software packages include the ability to create and attach an ECO to your design package; however, the best practice is to discuss modifications directly with your CM.

How do I order testing for my PCB assembly?

The best CMs will institute standard PCB assembly testing to ensure good solder joint quality. However, for functional testing—provided your CM provides this service—design changes must be made and specifications must be included in your design package to convey these requests, as the assembly process is significantly impacted. For example, in-circuit tests (ICTs), such as Flying Probe and Bed-of-Nails, may require fixtures to be built and software programming for data acquisition.

Do I need to order PCB assembly cleaning?

Building circuit boards inherently creates some debris that virtually all CMs will remove from your board. However, dedicated processing of your board to remove microscopic contamination may not be a part of your CM’s typical assembly procedures unless your application and applicable standards (medical devices are a good example) require it. If your board’s application is not in a critical industry such as medical devices, automotive or aerospace, you should make sure to order cleaning if desired.

Tempo’s Software-Driven Smart Factory Delivers the Industry’s Leading Custom Turnkey PCBA Manufacturing Services
  • Virtual PCBA Contract manufacturing.
  • Rapid, accurate quotes.
  • DFM support from Day 1 of design.
  • Digital Thread Processing with real-time monitoring.
  • Fastest turnaround times in the industry to maximize ROI.
  • QC certified Agile Manufacturing process to support risk management.
  • Standard and Advanced QC testing.
  • Worry-free supply chain continuity.
  • Specialization in rapid prototyping and low-volume production.
  • PCBA development optimization for complex critical system industries like Aerospace, Medical Devices, Automotive, and Industrial.

Not only do we clean every PCB assembled, but here at Tempo Automation, we lead the industry in building high-quality boards for prototyping and low-volume production the fastest. Our service includes working with you early during design to ensure that your design intent is maintained throughout the entire manufacturing process.

And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.

If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on the essentials of how to order PCB assembly, contact us.

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