Estimating Your flexible PCB cost
What is Flexible PCB (FPC)
Flexible PCB are flexible printed circuit boards, where the PCB stands for "printed circuit board". The correct abbreviation for flexible printed circuit boards would be FPC for "flexible printed circuit", since the "B" for "board" would be a "plate" and therefore rigid. Colloquially, the term “flexible PCBs” is widely used. Like conventional, rigid printed circuit boards, flexible printed circuits can be used as carriers for the electrical connection of components. A far more common use, however, is to connect rigid circuit boards together, as a type of cable, or as a flexible extension for positioning e.g. sensors. Flexible PCBs are also used as keypad foils.
How much does a flexible PCB cost?
Flexible printed circuit boards are always manufactured individually according to the data supplied and go through many processes until completion. The costs at Hemeixin for some prototypes start at around 200 USD. However, if the flexible printed circuit boards are later mass-produced in larger quantities, they may cost less than 1 USD or only a few cents. It is therefore difficult to make a general statement. If you are interested, simply send us your data or specifications and we will be happy to calculate the prices for you.
Cost and Price of a Flexible Circuit
In the right application, flexible circuits can reduce wires, eliminate connectors and rigid circuits. They might also simplify component assembly and reduce wiring errors. But competitive products such as rigid circuits, wires and connectors also have their place in the interconnection packaging world. These substitute products all can offer cost effective solutions and may be the best overall packaging answer in any individual application. Knowing what drives the cost in a flexible circuit can help steer a design.
While many factors affect the cost of fabricating a flexible circuit, I would suggest there are three overarching cost drivers:
Physical Size
Size matters, but it isn’t a simple calculation of square inch area. In the world of rigid printed circuit boards (PCB’s), prices are often quoted in price per square inch. This simplification can work reasonably well with a commodity grade product but even with rigid PCB’s, area based pricing is usually offered with a few “it depends” qualifiers.
The vast majority of flexible circuits are processed in rectangular panels. In the US, “standard” sizes are usually 12” X 24” and 18” X 24”. Fabrication of larger circuits is possible but special materials and equipment are required. Material optimization is accomplished as the individual parts are “nested” within the panel. Reverse nesting is a common term used to describe how two parts might be interlocked together with a 180 degree turn to allow best material utilization. Whether the panel has 100 individual parts or 2, the labor and materials per panel is about the same. Panel borders have rules defining “keep out” regions for tooling, and the required distance between adjacent circuits also affects nesting density. Further complications occur with automated component placement as assembly occurs on a subset of the manufacturing panel and conventions for assembly handling need to be accommodated. Deciding between maximizing circuits per panel vs. expedient assembly can be a balancing act between the competing interests of a fabrication house and a contract assembler.
Understandably, the more circuits nested on a panel, the lower the cost per circuit. In some situations a flexible circuit is in panel form through nearly the entire fabrication process. In other cases, the flex circuit may be singulated and have subsequent “personality” steps involved such as folding, connector assembly, or stiffener attachment. In the latter case, costs are driven by the value add to the individual part, so the cost formula changes.
Circuit Construction
The number of conductive layers in a flexible circuit is also a major cost factor. Double sided (2 layer) circuits will often be priced at 1.5-2X vs. an equivalent sized single layer circuit. More expensive material costs are one reason, but the added capital equipment and processing steps are a bigger factor.
As 4, 6 and 8 layer circuits are priced, the estimated yield loss also becomes a significant variable. As additional layers are added to the circuit, sequential processing steps are required. It is not unusual to have 40 or 50 process steps during fabrication. And if each process is 99.5% yield, a part with 40 steps will only yield 82%. An error near the end of the process can be expensive…both in cost and delivery timing.
Volume
Although there are niche circuit shops specializing in low volume and quick turn delivery, most fabricators are trying to cover engineering and overhead costs with low volume builds. Supplier support for low volume programs is often done as a necessity if higher volume quantities are to be captured. A lot charge for a low volume quantity of parts is pretty common. “Soft” tooling to cover part number costs is required as each circuit is custom requiring unique artworks, drill files, electrical test programs, inspection files and excising files. A non-recurring charge might also be expected.
As production volumes increase, fixed costs are spread out over a larger number of parts. More expensive and precise hard tooling is sometimes offered with high volume circuits. Laser technology is also used widely for singulation in flex circuit fabrication, offering excising precision without the fixed cost of tooling. Laser costs can be a bit more expensive for an individual circuit, but adoption does help avoid or delay a commitment to a more costly tooling package.
Pricing Generalities
In the world of printed circuits, the relationship between cost and price can be pretty tenuous. With niche players segmenting the market by volume, delivery time, market desirability and targeted customer penetration strategies it is easy to understand why significant variation in pricing occurs among different suppliers. This variation can be further complicated by how busy a factory is at any given time. With this abundance of constantly changing variables, it is pretty difficult to make generalizations about product pricing.
Advantages of flexible printed circuits
The advantages of flexible printed circuits (FPC) are manifold:
- flexible
- very thin
- Flame-retardant, class 94V0
- solderable
- inexpensive
- customizable
Furthermore, flexible printed circuit boards can be expanded with various special options for special applications, such as shielding foil, partial stiffening or “dimples” for better contacting, such as with ink cartridges on a printer.
Material & properties of Flex PCB
A typical material for flexible circuit boards is polyimide (not to be confused with polyamide). Polyimide itself has a higher temperature resistance than the standard FR4 material used for rigid PCBs. However, many flex PCBs also use epoxy, e.g. when a masking film is applied as a solder stop. There are also various flexible base materials, some of which contain layers of epoxy. For example, epoxy is used to apply the copper layer to the polyimide. As a result, the temperature resistance of the entire flexible printed circuit board is reduced again compared to pure polyimide (adhesive-less material).
Types of flexible printed circuit boards (FPC)
With flexible printed circuit boards, a basic distinction must be made between adhesive-free (or adhesive-less) and adhesive-based material. Adhesive-less FPCs do not contain epoxy in the base film (as the base material of FPC is also called because it is so thin). Here, the copper is rolled (annealed) directly onto the polyimide. Adhesive-free materials are therefore usually even thinner and are used when, for example, there are higher temperature requirements or epoxy must not be present in the application for other reasons.
Flexible printed circuit boards
With adhesive-based FPCs, the copper is bonded to the polyimide with a thin layer of epoxy. So you have thin, flexible mixed material structures. This is the cheaper and more common type of FPC base material and has no disadvantages compared to adhesive-free material for normal requirements.
Rigid-flex printed circuit boards
Another evolutionary stage of the flexible circuit FPC is the so-called rigid-flex PCB or rigid-flex circuit board. The abbreviation for this is “RFPCB”, which stands for “Rigid-Flexible Printed Circuit Board”. This is a combination of each one or even more rigid and flexible printed circuit boards in one circuit design. Since rigid-flexible printed circuit boards are a completely separate technology, we have compiled the information for you here.
The production of our printed circuit boards
The manufacturing process for flex circuit boards FPC is largely the same as for the manufacture of rigid circuit boards, with the biggest exception of handling. There are certain differences in the application of coverlay instead of wet solder mask. Here, a adhesive-based coverlay is used, in which the openings for the pads have been cut out beforehand. Due to FPCs sensitivity, some surface treatments are done with chemical processes, rather than mechanical ones. Another deviation is the separation, since flex circuit boards are usually either lasered or punched.
Common FPC Addons - Stiffeners & 3M
In order to use flexible printed circuit boards in their application in an even more targeted manner, the usual additions are stiffeners (reinforcements) and 3M adhesive foils. On the one hand, stiffeners are used to reinforce flex connector areas to a certain thickness (usually to a total thickness of 0.3mm), so that these connector ends can be plugged directly into sockets (usually ZIF/LIF). Such stiffeners are usually made of polyimide. Other reinforcements can also be made of FR4 and stabilize areas where components are placed, for example. Because components should never be located in bendable areas, as these could then break off quickly under load.
3M film is a double-sided adhesive film that allows the flexible circuit boards to be placed partially or over the entire surface like a sticker in an application. The 3M adhesive we use is suitable for reflow soldering. Both options are available in our online calculation.
Buy affordable flex printed circuit boards (FPC) directly from manufacturer
Hemeixin offers industrially manufactured, inexpensive flex boards on request by mail. You can choose between different materials, for example between adhesive-free and adhesive-based polyimide. Different thicknesses of stiffeners for ZIF/LIF connectors can also be attached, or a partial 3M adhesive film for easy gluing of the flex PCB into their application later. Other special options for FPCs you can find on our special technology site.
