Bare boards are printed circuit boards (PCBs) without the electrical components, through holes, or full circuitry. Bare boards only have a substrate, metal coating, and conductive pathways, allowing full control and flexibility of the components and design.
The benefit of a bare board is that it offers early testing to determine its efficacy. With testing measures, you can see if your board will function as it should before it’s fitted with expensive electrical components and circuitry.
There are numerous applications for bare boards, including consumer electronics, medical devices, automotive uses, and industrial applications. With testing measures, bare boards offer significant benefits and improvements to the overall PCB design process.
Why Gerber Labs?
Gerber Labs is your partner-in-design to help you bring your engineering vision to reality. We manufacture superior PCBs and bare boards at great prices, with full testing and design capabilities.
As a leader in bare board and PCB board manufacturing, we can create configurations of bare boards based on your custom specifications to ensure your design meets your budgetary and capability demands. We can assist with penalization, mounting, and plating for your bare boards, and we have in-house engineers to provide guidance and advice throughout the process.
Benefits of a PCB Bare Board
Bare circuit boards have numerous advantages. Initially, the bare board costs less since the testing takes place early in the design process. You can identify issues early on and adapt the design before too much of the development takes place, also saving time and gaining a competitive advantage with time-to-market.
Bare board testing is highly reliable. Because bare boards are tested early, you can determine if it can withstand the soldering process for expensive and complex components in the future. At Gerber Labs, testing can be done for prototypes and small production volumes, helping you to refine your design before it moves into high-volume production.
Bare Board Manufacturing Processes
The Pre-Production Step
A Gerber file is created and sent to the manufacturer with all the customization and production information. The in-house engineers then align the specifications with the desired capabilities for compliance.
Inner Layer Imaging
The imaging process defines the circuit traces. This is done with a focused laser beam that defines the circuit pattern directly into the board.
Inner Layer Etching
Using an etching process, all copper residue is removed from the board to ensure the copper circuitry pattern is in line with the design.
An oxide layer is applied to the inner board layers and then stacked together, creating insulation between them. Copper foil is also added.
During this step, holes are bored into the board to act as electrical contacts and optimize the layer links.
Electroless Copper Deposition
A thin copper layer is deposited into the drilled holes, concealing them and sealing off the whole board.
Outer Layer Imaging
Similar to the inner layering process, outer layer imaging removes the dry film to ensure the circuitry runs as it should. Then, extra copper is plated.
Extra plating is done in dry film parts as a second electrolytic plating process. Once the copper is deposited, tin is added to prevent oxidation.
Outer Layer Etching
Dry blue film and excess copper residue is removed. The tin deposits protect the essential copper components on the circuitry.
Using UV light, some aspects of the PCB are exposed and others are removed, then the entire board is cured with a solder mask for a smooth, quality finish.
Surface Finish Process
The surface finish process is designed to provide a solderable surface, which may be metallic or organic.
Bare boards are tested to ensure they’re functional up to desired standards and free from defects. Boards may be tested using a flying probe, fixtureless testing, or universal grid testing.
Profiting and V-Scoring
Following the production file, production panels are routed into specified sizes and shapes. The V-scoring process cuts a V-shaped groove at the top and bottom of the board, making it easy to separate from the other layers or components without damage.
Final Visual Inspection
A team of engineers inspects the product and visually examines the board to ensure it meets desired standards.
Packaging & Delivery
Products are wrapped and packed carefully, then shipped through the desired shipping service.
Contact us to discuss your bare PCB board project!
Bare Circuit Board Capabilities
|Board layers||Up to 12 layers|
|Bare board types||Single-sided, double-sided, multilayer, rigid, flex, rigid-flex|
|Thickness||Maximum: 0.13” Minimum: 0.025”|
|Base materials||FR-4, FR-406, G10, CEM3, Rogers, Alumina Ceramic|
|Copper weight and minimum trace width||0.5 oz (trace width 4 mil), 1 oz (trace width 5 mil)
2 oz (trace width 7 mil), 4 oz (trace width 12 mil), 6 oz (trace width 20 mil), 8 oz (trace width 40 mil)
|Minimum conductor width and space||0.003”|
|Minimum hole size||0.006”|
|Legend colors||Black, white, pink, yellow, red|
|Solder mask||Black, green, red, purple, blue, yellow, gold, silver|
|Maximum hole aspect ratio||10:01|
|Surface plating||Tin/lead, soft or hard gold, tin, silver, OSP|
|Testing||Isolation testing, continuity testing|
Depending on the details of your design and project, the average turnaround time is X working days. We can expedite the process to as little as X days, however.
Bare Board Product Images
Designing a Bare Board
Designing a bare board is similar to designing a PCB.
Step 1: Design and Output
The bare board you design must have a layout in the appropriate CAD software, such as Altium Designers or KiCAD. The manufacturer will need the software information used to design the circuit and ensure the build is true to the original design.
Once the design is approved, you can export the file into the manufacturer’s desired output format. In many cases, this can be done using an extended Gerber file, which encodes information like component notations and tracking layers.
All boards are put through inspections to check for errors or defects. Then, you can plan components like trace hole spacing, hole size, track width, and board edge spacing before forwarding the file to the manufacturer for production.
Step 2: Output the Schematic Files
The schematic files need to be outputted for the manufacturer to create photo films, which are then used to image the board. Designers can use plotters to create detailed designs.
You should have a plastic sheet with a negative film for your PCB, which indicates the conductive copper components. There’s also a film layer that covers the vital non-conductive material. Each layer of the board should have a black film sheet.
Step 3: Inspect the Board
Visual inspection is only useful for a two-layer PCB. Testing can be done manually or using automated devices for two-layer boards, but multilayer boards will need electrical testing to ensure efficacy.
There are two types of electrical testing commonly used: universal grid and flying probe. Universal grid requires fixtures for testing, while the universal grid does not.
Testing may be resistance or capacitance testing. Resistance tests measure the flow of current, while capacitance tests identify opens and shorts.
Bare Board Packaging and Shipping
Once design, prototyping, testing, and production are complete, the bare board is ready for shipping. Each board is meticulously packaged according to international delivery standards, then shipped using the desired shipping carrier.
Bare Board Fabrication and Assembly
Once the manufacturer has all the design information, fabrication can begin on the raw board. Many bare boards can be fabricated using single-sided boards and multilayer boards.
Step 1: Create the Circuitry Images
The first step is to transfer the design circuitry image data from the Gerber manufacturing files to the board. This image data may be transferred using:
Photo tooling: Standard imaging process that uses a photoplotter to create circuitry images on film, which is then printed on the board.
Direct imaging: A laser prints the circuitry images directly onto the board. This is a more precise method and eliminates the need for photo tooling. For multilayer boards, each board must be printed individually, which makes the process more expensive.
Step 2: Create the Layers
A multilayer board has several layers of dielectric material and metal conductors, multilayer boards are laminated together with other core structures, and each layer must be produced and controlled for the appropriate alignment, width, copper weight, and more, ensuring a quality finished product.
Step 3: Create the Inner Layer Circuitry
The circuitry images must be printed onto the inner layer cores, which involves photoresist material. This material covers the copper foil of the core, then the photoresist is exposed to UV light or printed using direct imaging.
Only the copper circuitry is polymerized in the process, leaving unexposed photoresist to be chemically removed. The copper layers are etched away, leaving the protected circuitry.
Once this process is complete, the layers are inspected by an automated optical inspection for defects. Each layer goes through this process, then all layers are laminated to create a completed board.
Step 4: Laminate the Layers
Layered boards are stacked to create a multilayer board. Each layer is coated with “prepreg,” a fiberglass material with epoxy resin that can withstand the high heat of lamination. As the boards cool, the prepreg bonds the layers together.
The lamination phase is one of the most challenging, since compositing the board requires attention to detail to ensure correct alignment.
Step 5: Drill Holes
The board needs holes for through-hole vias and component mounting. Most through-holes are plated and drilled with a larger diameter to allow for plating. Boards with blind or buried vias are fabricated before the lamination, which adds cost to the process but may be necessary for performance.
Once drilled, the holes are cleaned using chemical processes. The entire surface of the board is cleaned and chemically coated with a thin copper layer for electroplating.
Step 6: Surface Finishing
For protection during assembly, a solder mask is used to cover the entire board, except the metal pads and soldered features. Markings are silk screened onto the board. Both the solder mask and silkscreen are cured by baking.
The board will also have a surface finish for the exposed metal surfaces for protection. Usually, boards are coated and then dipped in molten solder, then high-pressure hot air is used to remove excess solder and smooth the surface.
Step 7: Assembly and Testing
The final step of the process is assembly. If needed, the boards may be routed out of manufacturing panels with V-shaped cuts on the board outline or small breakout tabs.
The finished board may be tested with continuity testing or flying probe testing, which look for defects or performance issues. When testing is complete, the board is ready for component assembly.
Bare Board FAQs
What is a bare board?
A bare board is a printed circuit board without the electric components or through holes. It’s only a substrate, metal coating, and conductive pathways.
Can I create multilayer boards?
Yes, Gerber Labs can create single, 2-layer, 4-layer, or multilayer boards.
What is the maximum board size you offer for bare boards?
The maximum bare board size is X x X.
What materials can bare boards be made of?
Bare boards can be made of FR-4, FR-406, FR-408, G10, CEM3, Rogers, alumina ceramic.
What is bare board testing?
Bare board testing, like PCB testing, ensures that the board and its circuitry will function as intended.
Can you test my board?
Yes, Gerber Labs offers bare board testing using a variety of methods.
What’s the advantage of bare board testing?
Testing in advance identifies problems or defects in the design or its function, so it can be corrected before production.
Do bare boards cater to blind and buried vias?
Yes, our boards cater to blind and buried vias.
What services do you offer?
We offer PCB fabrication, PCB assembly, and full turnkey services.
Can I expedite my bare board production?
Please contact us to discuss your bare board requirements with us and see if we can meet your turnaround needs.
Why Gerber Labs?
Gerber Labs is known for its high-quality PCB bare boards crafted to your unique specifications. Our bare boards can help you with penalization, fitting your bare board to larger boards, and mounting and plating. We configure your boards according to your specifications and can test your bare boards effectively.
Ready to get started? Contact us to discuss your project needs!