How to Reduce Rigid Flex PCB Costs

01 November 2022
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Rigid flex printed circuit boards (PCBs) are highly versatile circuit boards that incorporate aspects of both hardboard and flexible circuits. They are typically composed of multiple layers of rigid circuit boards with layers of flexible circuitry buried within the hard boards.

Although rigid flex PCBs come at a higher cost than rigid PCBs, they are more versatile and easier to tailor to the needs of specific applications. Rigid flex PCBs are particularly useful for military, aerospace, and medical applications, where they exhibit resilience to high levels of shock and vibration. They are easier to assemble into precise applications, and their smaller and more flexible configuration makes them well suited to electronics where circuit weight and space are of particular consideration.

When appropriate, cost-saving measures can be exercised to make sure you are still able to get the best value from rigid flex PCBs. The number of circuit layers, materials used, and design processes can all be tailored to meet the needs of your application.

Rigid Flex PCB Cost

Rigid flex PCBs are approximately seven times more expensive than an equivalent rigid PCB, largely due to the raw materials required, and in general lower overall yields.

Rigid flex PCB's use materials that are common to hard board and flexible circuit PCB manufacturers -core laminate, prepreg, copper foil, flexible laminates, coverlayers and bondplies. But some are unique to rigid flex manufacturers and cost more than traditional PCB materials.

One of the most critical components to successful rigid flex PCB manufacturing is the use of no or low flow prepregs. No flow prepregs are necessary to prevent the flow of resin out onto the flexible sections of the boards. They flow eno ugh to go to the edge of the rigid, without flowi ng out onto the flex arms.

No flow prepregs gen erally cost about 10X traditio nal FR4 and polyimide prepregs. Additionally, they are only available in two glass fabrics -106 and 1080, which are thin. Rigid flex manufacturers do not have the option of using some of the lower cost, and thicker fabrics, such as 2113,2313,2116,1652 and 7628 because they are not available in no flow variants. Consequently, rigid flex PCB manufacturers use a more expensive ply of prepreg, and at the same time need to use more sheets to glue the final composite package together.

Also, because it is a no flow resi n, it is gen erally risky to use a single ply of prepreg, typically utilized by hard board manufacturers to reduce board costs. Two plies are usually essentiai to assure adequate encapsulation of the internal circuitry - another factor that increases cost of rigid flex designs.

One cost driver in rigid flex PCB manufacturing is the flexible copper clad laminates within the package. There are many d if fere nt typesof flexible laminates in the World - polyester, PEN, polyimide, and even paper, etc. Some are made with adhesive systems to Bond the copper onto the base film, and some are not. Rigid flex manufacturers to improve yield, use almost exclusively adhesiveless laminates with polyimide base materials - gen erally one of the more expe nsive flexible lami nates available. Additionally, con trolled impedance designs, gen erally require thicker polymide films, to make the impedanee circuits function properly. Those materials come at an exp on entially higher cost than the thinner materials.

Rigid flex boards are built in separate compo nents and then assembled in to the final board - addi ng processi ng steps and complexity, which in creases cost. In gen eral, slower, more conservative and intentional manufacturing methods are used by rigid flex PCB fabricators to achieve better manufacturing yields.

The last thing that impacts the cost of rigid flex PCB boards is overall manu facturing yield. Rigid flex PCB boards com bine materials with very dissimilar dimensional stability characteristics. Getting those dissimilar materials to register to one an other requires experie nee, specialized equipme nt and software tools. Even with those though, yields in rigid flex PCB manufacturing are in here ntly lower tha n hard boards or conven tional flexible circuits.

The overall cost of rigid flex PCB manufacturing can, therefore, be reduced by choosing materials carefully and tailoring the material set to the specific needs of the application. The less material used, the greater the reduction in manufacturing costs. We recommend working closely with your rigid flex PCB manufacturer to find out if raw material costs can be streamlined for your specific needs.

For a good starti ng poin t, for desig ning low cost rigid flex PCB designs, con suit our Valu Build Brochure that is available here. The Valu Build program gives material layups and suggestions to provide you with optimized cost solutions for your design.

Minimizing Rigid Flex PCB Design Costs

You can further lower the cost of rigid flex PCBs by tailoring the material to minimize the layers, thickness, and overall costs. Some of the major considerati ons that will affect the cost of your PCB design in elude:

Keep overall layers to a minimum:

Reducing the number of layers in your design, reduces the number of plies of prepreg required to bond your board together. At the same time, fewer layers optimize the ability i of the manufacturer to improve manufacturing yields - both of which reduce your overall cost.

Keep flexible layers to a minimum:

The flexible laminate is more expensive than the rigid laminates. Limiting the number of layers of flexible circuits, reduces your overall cost for the board. The flexible layers are constructed separately from the final rigid flex board, which also adds to their cost. Reducing the layers of flexible circuitry on your design, lowers your overall package cost.

Use rigid board laminates to achieve overall thickness:

If you are attempt!ng to achieve a specific overall thickness, try to do so using the rigid board laminates, rather than additional plies of no flow prepreg or flexible laminates. The rigid laminates are the lowest cost material in the construction.

Limit controlled impedance requirements:

In high speed designs, it is tempting to define all the impedanee values that you wish to achieve. And this is fine, and you should employ your fabricator to help model all the impedanee values you desire. However, the print should list only the impedance traces that you want tested. With rigid flex desig ns and test coup ons required for the flexible sections as well as the rigid sections, the impedanee coupons can get very large very quickly, removing parts from the production panel. It is wise to model and test only those impedanee values your design truly needs.

Have all flexible arms in the design terminate in rigid boards:

Often rigid flex PCB designers want one or more arms to end in a flex cable, typically for mating with a zif connector or other device. They do not desire the thickness or rigidity of the hard board in these sections. To achieve this feature though, the rigid flex PCB manufacturer must incorporate a technique called "pouching" to protect the flex arm, during outerlayer manufacturing. Pouched rigid flex boards require a lot of extra hand processing to build them successfully and should have strain relief beading applied to the rigid to flex transitions area - a subsequent hand applied material. Having all flexible arms terminate in rigid boards affords you the lowest possible cost for your design.

Specialized processing:

There are techniques that are very common to rigid board designs that are much more difficult to achieve reas on able yields in rigid flex PCB designs. Because they are difficult to achieve, they create lower overall manufacturi ng yields, that in crease the cost of your part. Some of the most comm on elements are via in pads requiring filled vias, dual surface finishes such as ENIG and electroplated nickel gold or hot air leveled solder, buried, blind and laser vias, innerlayer copper thicknesses greater than three ounces,: blue and black soldermask, and V scoring can all present challenges for your fabricator. Consult your fabricator for advice on what they would suggest for improving the cost of your design.

Manufacturing Cost Considerations for Rigid Flex PCBs

In addition to optimizing material usage and design parameters, the configuration of the PCB can be simplified to further reduce man ufacturing costs. The size, shape, complexity, and con figuration of a board will affect the cost of materials and assembly. Any additional plated slots, edges and other customized design requirements will reduce yield and further inflate the cost.

Early involvement of the fabricator in the product design process allows the fabricator to produce PCBs optimized for the end application, without the need for costly adjustments or redesigns. A full assessment of available manufacturing options can be conducted at the beginning of the design process. This careful planning will ensure the design is optimized for use in the desired applications, a successful first time build, while accounting for expected product variations.

How Much Does an HDI Rigid-Flex PCB Manufacturer Cost?

HDI PCBs naturally cost more than a standard PCB, particularly if you require Type IV, V, or VI stack-ups in your circuit. There are a few factors that can affect how much your overall fabrication and design process will cost. For example, boards that require higher frequencies need to be made of gold, silver, or other higher-grade materials.

If you require a PCB to be made for a high-tech device, you’ll require more layers. Circuits with more than one layer or with components on either side are costlier. Since PCBs require numerous components, there are multiple layers stacked on top of each other. As components take up more space, the board needs to be larger, and thus, more time and money are needed to manufacture these kinds of PCBs.

PCBs also feature holes, which can raise manufacturing costs. Precision drilling is required for these holes, particularly when the motherboards are thick or compacted. Moreover, skilled experts are needed to manufacture your boards, and often they need to use automated machinery for the process. The cost of generating a PCB is influenced by labor expenses, and no one wants untrained workers to create these critical components for complicated electrical gadgets.

The type of technology the HDI Rigid Flex PCB manufacturer uses is also a factor. For example, surface-mount technology costs less than through-hole technology. In general, you can expect a standard PCB to cost $10 to $50 per board. However, the actual price can only be determined by the fabricator themselves. It can vary with the components, type of material, and size of your PCB.

How Can You Calculate the Cost of Rigid flex PCB Fabrication?

PCB Fab Houses establish prices based on a variety of criteria; hence, there is no standard method for calculating PCB fabrication costs. Each HDI Rigid Flex PCB manufacturer can have its own formula to calculate the total cost.

Furthermore, the payback is already included in the PCB manufacturing cost you determined using their respective online PCB Price Calculators. This is one of the reasons why different fabricators can quote the same HDI PCB manufacturing order differently.

When you approach an HDI Rigid Flex PCB manufacturer, make sure whether they make high-quality boards at a reasonable price. Sharing as much detail about your product as possible will help your manufacturer give you a realistic and more accurate quote.

How To Make HDI Rigid flex PCB Manufacturing More Economical

The first stage in constructing a printed circuit board is to determine the most cost-effective materials that meet the application's requirements. Material data sheets and pricing lists provide fundamental information, but they don't tell you how much it would cost to construct the board with one material over another.

Datasheets frequently indicate two materials with virtually comparable properties, but one can be more or less difficult to handle than the other, particularly with HDI technology. When consulting with an expert about your prototype, you should ask them to help you identify materials that would give the optimum result while balancing price, performance, and manufacturability based on your design.

Tailoring your PCB design to fit your needs can help reduce the cost. The number of layers directly affects how much your PCB is going to cost. Hence, keeping the layers to a minimum will lower the cost. This makes it easier for boards to bond to each other and give a better manufacturing yield rate. Consequently, material costs are reduced when a higher quality product is made without requiring additional materials.

Flexible laminates cost more than rigid laminates, so a circuit with more flexible circuitry can increase the overall price. Similarly, although the demand for high-speed design is appealing, there are certain drawbacks. Controlled impedance needs should be confined to the tested levels desired in production panels. This reduces the cost of producing large coupons for both sections with many pieces removed from your circuit, which can soon add up.

Another way you can drive down your overall cost is by ordering in bulk. The cost of manufacturing decreases with a higher volume. So, ordering more units can end up saving you more money than if you were to order a single unit.

Final Words

With the portable communications industry expanding rapidly, flex PCB fabrication is becoming recognized as a popular design strategy for both advanced component surface mounting requirements as well as sophisticated, three-dimensional product construction. As more complex designs become more expensive, it is important to have tips to reduce the cost wherever possible.

Although more expensive than traditional rigid counterparts, the manufacturing costs of rigid flex PCBs can be significantly reduced using thoughtful engineering that reduce unnecessary complexity and material usage. In addition, the savings in product design, logistics, and assembly make rigid flex PCBs a cost effective option.

At Hemeixin, we can help you design and manufacture multilayer rigid-flex PCBs as well as flexible PCBs and HDIs for a variety of high-reliability purposes or applications. You can get in touch with our HDI Rigid Flex PCB manufacturer to get a clearer idea of which design suits your desired application. For an instant online quote for your project, you can use our HDI Rigid Flex PCB Fabrication Cost Calculator.

For more than 15 years, Hemeixin has been providing cutting-edge PCB technology for customers around the world. We are dedicated to providing the highest quality rigid flex and flexible circuits in the industry. To learn more about reducing rigid flex PCB costs, contact us today.