PCB Capabilities
Flex PCB Manufacturing
Single-sided to multilayer flexible circuits on polyimide substrates.
Flexible PCBs use polyimide substrates that bend, fold and conform to three-dimensional shapes impossible for rigid FR-4 boards. Flex circuits replace wire harnesses and ribbon cables in applications where space is tight, weight matters, reliability is critical, or the circuit must move during product operation. AstroPCB manufactures single-sided, double-sided and multilayer flex PCBs with polyimide substrates, coverlay protection and stiffener reinforcement where needed.
Flex PCB construction types
Single-sided flex is the simplest and most cost-effective construction: one copper layer on a polyimide base film, protected by coverlay on the component side. Single-sided flex is common for LED strip interconnects, sensor cables, battery pack connections and simple signal routing between two rigid assemblies. Double-sided flex adds a second copper layer, enabling routing on both sides with plated through-holes connecting the layers. Double-sided flex supports more complex circuits including impedance-controlled differential pairs, power and ground distribution, and moderate component density.
Multilayer flex stacks three or more copper layers with polyimide dielectric layers between them. Multilayer flex provides the routing density needed for complex interconnects but increases thickness, reducing flexibility. The design must balance routing needs against the minimum bend radius — more layers mean thicker construction and larger minimum bend radius.
Polyimide and coverlay
Polyimide film (typically Kapton or equivalent) provides the base substrate. Standard thicknesses are 12.5, 25 and 50 microns (0.5, 1 and 2 mil). Thinner polyimide enables tighter bend radius but is more difficult to handle during fabrication. The copper is bonded to the polyimide either with adhesive (acrylic or epoxy adhesive layer between copper and polyimide) or without adhesive (copper cast or laminated directly onto polyimide). Adhesiveless construction provides better flex life, thinner profile, improved thermal performance and more consistent electrical properties.
Coverlay is the flex circuit equivalent of solder mask. A polyimide film with adhesive backing is die-cut to expose component pads and laminated over the circuit. Coverlay provides mechanical protection for the copper traces and acts as the outer dielectric. Unlike liquid solder mask used on rigid boards, coverlay maintains its integrity through repeated flexing without cracking.
Dynamic vs static flex
Static flex bends during installation and remains in the bent position throughout product life — a board folded to fit inside a curved enclosure, for example. Dynamic flex bends repeatedly during product operation — a printer head cable that flexes millions of times over the product’s life. Dynamic flex applications require rolled annealed copper (better fatigue resistance than electrodeposited copper), adhesiveless construction (no adhesive layer to delaminate), and generous bend radius (minimum 6-10x the circuit thickness). Static flex can use electrodeposited copper and adhesive-based construction at tighter bend radii (3-6x thickness).
Stiffeners
Stiffeners are rigid material (FR-4, polyimide, stainless steel or aluminum) laminated to specific areas of a flex circuit to provide mechanical support for connectors and components. A ZIF connector soldered to a flex circuit requires a stiffener behind the connector area to prevent the flex from bending at the solder joints during cable insertion and removal. Stiffener material and thickness are selected based on the mechanical support required.
Request a flex PCB quote
Specify layer count, polyimide thickness, copper type (RA or ED), adhesive or adhesiveless construction, bend radius and stiffener requirements. Upload design files for a DFM-reviewed quotation.