Flexible Circuits & Assemblies

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Flexible Circuits

Flexible circuits, also known as flex circuits, flat flexible circuits (FFC's), or flexible printed circuits (FPC's), are an innovative solution to the ever-growing demand for lighter, thinner, and more compact electronic devices. These circuits are made from thin, flexible materials that can bend and flex without compromising their functionality. As technology continues to evolve at a rapid pace, flexible circuits have become increasingly popular in a wide range of industries, from consumer electronics to aerospace and medical applications.

ALMAX has been designing and manufacturing flexible circuits for over 20 years. As a result, our flexible circuit capabilities are top of the line. With our expertise and guidance, we can help bring your flexible part to life.

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The Benefits of Flex Circuits

Flexible circuits, also known as FFC’s or FPC’s, are a special type of durable circuit that can be bent into any desired shape without being damaged. Flexible circuit technology is highly reliable and provides key benefits beyond other available methods. These include reduced packaging requirements, high wiring density, shock and vibration performance, high-speed signal performance, harsh environment performance, and significant cost savings. They can also be manufactured using a multitude of various substrates and conductive materials. Additional benefits include:

Flexible Circuit
Layer Stacks

Flex circuits can be classified into several different types, based on their construction, functionality, and materials used.

1. Single-Sided Flex Circuits: These circuits consist of a single layer of conductive material (usually copper) on a flexible substrate. They are the simplest and most common type of flexible circuit, and are typically used in applications that require simple interconnections.

2. Double-Sided Flex Circuits: These circuits have conductive material on both sides of the flexible substrate, allowing for more complex circuit designs. They are often used in applications that require higher circuit densities, such as mobile phones and wearable devices.

3. Multilayer Flex Circuits: As the name suggests, these circuits include multiple layers of conductive material, separated by insulating layers. This type of flexible circuit can support even more complex circuit designs and is often used in high-density electronic devices.

4. Rigid-Flex Circuits: These circuits combine the flexibility of flexible circuits with the rigidity of traditional PCBs, allowing for a hybrid solution that offers the best of both worlds. Rigid-flex circuits are commonly used in aerospace and medical applications, where both flexibility and rigidity are required.

Typical Components of Flexible Circuits

The main components of flex circuits include:

1. Components: Various electronic components, such as resistors, capacitors, and integrated circuits, can be mounted onto the flexible circuit to create a fully functional electronic assembly.

2. Conductive material: Copper is the most common conductive material used in flexible circuits, although other metals such as silver and gold can also be used. The conductive material forms the electrical traces, which connect the various components on the circuit.

3. Adhesive: An adhesive is used to bond the conductive material to the flexible substrate. There are various types of adhesives available, including thermosetting adhesives and pressure-sensitive adhesives.

4. Flexible substrate: This is the base layer of the circuit, made from a thin, flexible material such as polyimide or polyester. The substrate provides mechanical support and acts as an electrical insulator.

5. Coverlay: Also known as a cover film, the coverlay is a protective layer that shields the conductive material from environmental factors and provides electrical insulation. Coverlays are typically made from the same material as the flexible substrate and can be either laminated or adhesive-based.

Substrate Materials for Flexible Circuits

Polyimide Flex Circuits

Polyimide films have a high heat resistance, allowing them to withstand all the same soldering processes as typical rigid circuit boards can. These polyimide FFC’s are most popular for high-reliability, high precision type applications (military, medical, etc.), and dynamic flex applications.

Polyimide flexible circuits can be printed on with conductive inks, or etched with a sheet layer of copper.

Polyimide Flex circuits are also compatible with rigid-flex layer stackups allowing for more versatile applications.

Polyester Flex Circuits

Several different types of polyester are available. The polymer is thermoplastic and can thus be heat-formed if desired. This is oftentimes an overlooked advantage of polyester flexible circuits.

Polyester flexible circuits are not as heat-resistant as the polyimide form, making them suitable for only printed flexible circuit applications. These films are very popular in membrane switch constructions and are becoming more durable and conductive as the printed electronics industry continues to evolve.

Conductive Materials for Flexible Circuits

Conductive Inks

Conductive inks, as the name suggests, are inks that conduct electricity. They are commonly seen in capacitive and membrane switches, Radio Frequency Identification (RFID) tags, touch screens, biomedical and electrochemical sensors, Positive Temperature Coefficient (PTC) heaters, electromagnetic interference/radio frequency interference (EMI/RFI) shielding, and more. ALMAX has been manufacturing flexible circuits with conductive inks for over twenty years with inks such as: Micro-Silver, Nano Silver, Nano Copper, Silver-Silver Chloride, PEDOT:PSS, and Carbon.

Etched Copper Foil

A flexible circuit is a vast accumulation of conductors bonded to a thin dielectric or insulating film. In a copper flex circuit, a very thin sheet of copper is laminated to a flexible film substrate then chemically etched away, leaving copper traces. Copper flex circuitry construction offers significant benefits, including improved creasability, greater conductivity, and better adhesion.

Although typical flexible circuit laminates are made utilizing rolled and annealed copper, an abundance of metal foils of varying thicknesses are available from which to choose and construct a flex circuit.

Advanced Flex Circuit Add-Ons

BioMedical Sensing Inks

BioMedical Inks such as Silver/Silver Chloride are typically used to create sensing electrodes in many medical and environmental device applications. It is commonly used for electrochemical measurements, such as in pH meters, electrocardiography (ECG), electroencephalography (EEG), Transcutaneous Electrical Nerve Stimulation (TENS), or in cathodic protection corrosion systems for sea water environments and more.

Transparent Inks

Transparent Inks such as PEDOT are remarkable conductive polymers because not only are they Flexible & Printable, but also Transparent & Conductive. Usually, conductors are opaque due to their chemical composition. PEDOT, on the other hand, permits light to pass through, making it the perfect selection for applications that combine a need for both backlighting and circuitry, such as pairing LEDs with Capacitive Touch Switches.

Let's Talk About Your Flexible Circuit Needs

ALMAX provides top tier manufacturing for a complete array of flexible circuit technologies. From concept design to volume manufacturing, our partners entrust their custom flex circuit needs to our engineering and manufacturing teams. Our core competency resides in solving human interface challenges, and we recognized early on that of the many issues surrounding how flexible circuits were manufactured, the only proper solution for flexible circuit innovation to flourish required quality control across the entire flexible circuit manufacturing process.

Within two decades, we have expanded our operations to own three manufacturing facilities, including a domestic prototype facility, and two off-shore manufacturing plants providing high volume production capabilities. ALMAX has the capacity to offer our clients exquisite, high-quality, high-functionality flexible circuits due to our portfolio of facilities, processes and expert engineering for a plethora of industries.

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