How to control the rigid flex pcb cost

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.

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.

How to control the rigid flex pcb design cost?

Minimize overall layers:
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.

Minimize flexible layers :
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.

Overall thickness achieved by using rigid plate laminates:
If you are attempting 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 impedance values that you wish to achieve. And this is fine, and you should employ your fabricator to help model all the impedance values you desire. However, the print should list only the impedance traces that you want tested.

With rigid flex designs and test coupons required for the flexible sections as well as the rigid sections, the impedance coupons can get very large very quickly, removing parts from the production panel. It is wise to model and test only those impedance values your design truly needs.

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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 3OZ.

Blue and black solder mask, 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.

How to control the rigid flex pcb manufacturing cost?

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.

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