Flex PCB Assembly
Push the Limits of Electronics – Flex PCB Assembly Services from Mars PCB
Flex PCB Assembly at Mars PCB
Flexible printed circuit boards (often called FPCs) demand specific assembly approaches different from rigid boards. Because flex substrates bend easily, they cannot remain steady during standard surface mount procedures (e.g., applying solder paste, placing parts, and reflow). They require stable carriers that keep the flex material motionless through each manufacturing step.
A successful flex assembly demands fixtures, customized process settings, and extra care to prevent shifts and deformations. By using the right tooling plus close attention to details, flex boards can be reliably produced and deliver consistent performance. This thoughtful approach reduces rework and prevents defects, ensuring stable solder joints even under bending.
Mars PCB offers an end-to-end solution for flexible board manufacturing and assembly. We handle designs from one to twelve layers, coordinate bill of materials (BOM) sourcing, and conduct final inspection. Just share your drawings and BOM with us. We will quickly quote both fabrication and assembly for your flexible circuit needs.
Flex Assembly Process
Before components are mounted, flex circuits are baked at 80–100°C for about 4–8 hours. This step drives out trapped moisture, guarding against expansion or voids during solder reflow.
Flexible substrates are secured onto carrier fixtures so they stay flat and aligned. Precision tooling pins or holes help position the board. High-temperature materials, like silicone or engineered stone, help prevent warping while withstanding the heat of assembly.
The board is gently placed on the carrier and taped around the edges to avoid shifting. Spring pins can apply light force during printing. The time from mounting to soldering is kept short, and operators wear finger covers to avoid contaminating surfaces. Before each use, the fixture is cleaned to reduce dust or particles.
Solder paste is deposited through a laser-cut stencil onto the pads. Automated inspection monitors accuracy. Some setups add adhesive backing for extra flatness, ensuring consistent paste thickness on delicate flex layers.
Parts are placed onto the paste by robotic pick-and-place equipment. Carriers keep the flex circuit stable throughout. Optical alignment checks confirm each component is correctly oriented and in the proper location.
The populated board travels through a reflow oven, where the paste bonds parts to pads. The carrier system helps control warping and ensures the temperature profile is fine-tuned for delicate flex material.
Various methods—optical tests, X-ray checks, and electrical measurements—verify solder joints and board functionality. Failed boards can be reworked or replaced as needed.
Once tests are passed, carriers are carefully removed. A final visual exam confirms everything meets specifications before packaging and shipping to customers.
Flex PCB Assembly Characteristics
When compared to rigid boards, FPC assemblies bring a range of advantages but also extra complexity.
Below are a few notable traits of flex PCB assembly:
● Material Types – Flexible circuits rely on very thin polymer films (like polyimide) carrying metal traces. This structure folds and bends but can be fragile if handled improperly.
● Layer Options – Most flex designs use one or two copper layers, though advanced versions may go up to six or more. Having fewer layers allows for more bendable areas.
● Shape Flexibility – Because these boards can fold or twist, designers can create tight bends and even three-dimensional layouts.
● Interconnect Methods – Instead of plated vias, flex boards sometimes use bonding adhesives or unique solders for layer-to-layer connections. Ribbons or connectors also appear frequently.
● Assembly Flow – The use of carrier plates is standard for screen printing, part placement, and reflow. Certain components may come in specialized packages meant for flexible substrates.
● Inspection Challenges – Examining flex boards can be tricky. Automated optical or X-ray equipment must handle low-contrast surfaces. Test fixtures need reliable contact points.
● Durability – Because these assemblies can bend repeatedly, materials and solder joints must be able to endure stress over time.
By carefully controlling design features, assembly steps, and inspection measures, potential issues like misalignment, cracks, or repeated flex failures can be minimized.
At Mars PCB, we combine proven techniques with extensive industry know-how, creating flexible boards that are trustworthy and effective.
Core Equipment in Flex PCB Assembly
We invite you to contact Mars PCB for guidance on assembling challenging flex projects. Below are major pieces of equipment typically used when handling flexible boards:
A paste printer applies solder paste through stencils onto each pad. For flex builds, it needs to accommodate very thin substrates, often fixed on stiff carriers. Vision systems confirm accurate alignment.
Robotic pick-and-place machines arrange parts onto the wet solder paste precisely. Flexible feeders or custom nozzles might be needed for unusual shapes. Proper calibration is key for accuracy.
A reflow oven fuses paste and components into permanent connections. Heat levels and airflow must be controlled to protect flex materials. Even minor warping can damage fragile circuits, so gentle temperature gradients are essential.
These machines trim and shape leads for through-hole parts or connectors. This might be needed if certain flex assemblies have components that require special mechanical fits.
Wave soldering can still be used if flex boards must incorporate through-hole devices. However, boards usually need carriers and masking techniques to avoid exposed areas contacting hot solder waves.
Hand soldering or rework often requires magnification and anti-static conditions. Operators must be particularly cautious when working on thin flex materials to avoid applying too much heat or pressure.
ICT fixtures physically contact test pads to confirm functionality and spot open circuits or shorted nets. Because of the flexible nature, specialized fixtures are used to maintain contact.
FCT places assembled boards in a mock system environment to verify performance. Power signals and other I/O interactions are checked to ensure operational integrity.
Thermal cycling or vibration tests help identify early-life defects. Flex boards must withstand repeated flexing or temperature shifts, so screening can highlight potential reliability problems.
Different cleaning solutions (aqueous or solvent-based) remove flux residues from circuit boards. For flexible boards, gentle handling is critical to prevent folds or kinks post-assembly.
AOI utilizes high-resolution cameras to detect solder mistakes or misplaced parts. Because flex boards can have unique outlines, specialized software and fixture designs help ensure correct inspection angles.
Soldering Essentials for Flex PCB Assembly
Through-hole or surface mount pins should be well-seated to the board’s copper pads. Solder volume should be sufficient, avoiding partial coverage or bridging.
Ideal fillets create a stable cone or curved form along each pin and pad. Strong fillets guard against mechanical stress during flexing.
Solder needs to flow uniformly over both pads and leads, avoiding gaps or cracks that might reduce conductivity or mechanical strength.
Typical guidelines suggest at least 1 mm joint height on single-sided flex and 0.5 mm for double-sided designs. Uniform coverage under leads is crucial.
Look for a shiny, uniform finish with no leftover flux, voids, or lumps. Any lumps or spatter can lead to bridging or reliability concerns.
Headers or other leaded parts should sit flush on the surface without tilting. Overall part height deviation should remain within half a millimeter to preserve contact integrity.
Why Choose Mars PCB for Flex PCB Assembly
At Mars PCB, we focus on top-tier production of flexible circuit assemblies. Our 15+ years of industry experience and advanced factories in China enable us to deliver extraordinary quality and on-time performance for each project. We take pride in crafting robust solutions that meet your technical demands. Key reasons to partner with us for your flex assembly:
● Engineering Expertise – We have seasoned staff who know how to design and assemble complex flex circuits with minimal error rates.
● State-of-the-Art Manufacturing – Our lines use up-to-date pick-and-place machines, reflow ovens, optical systems, and more, tailored for delicate materials.
● Trusted Materials – We partner with reliable suppliers to ensure consistent, high-grade substrates, copper foils, adhesives, and protective layers.
● Strict QA Processes – Each stage involves inspections to catch issues early and maintain superb build quality.
● Flexible Capacity – With three production sites totaling 30,000 square meters, plus 500 skilled workers, we handle large volumes with ease.
● Competitive Costs – We balance affordability with top performance by optimizing each manufacturing step.
● IP Protection – We protect your designs and data to ensure confidentiality.
While keeping costs competitive, we are focused on meeting performance and reliability targets. Our experts work closely with you to optimize every step.
We handle both prototypes and large orders, managing a wide array of shapes and specifications to match your final product design.
We embrace thorough inspections, from visual checks to automated tests, ensuring stable performance before shipping.
Select a flex PCB manufacturer with a track record of delivering advanced circuit assemblies. Mars PCB continues to be recognized at home and abroad for quality and reliability.
Our plants have attained ISO9001, ISO14001, IATF16949, ISO13485, AS9100, and other major certifications, confirming we uphold rigorous global standards.
We use premium substrates tailored to your application and can guide you on the right stack-up for your project’s intended use.
Professional PCB & PCB Assembly Manufacturer & Factory
Reach out for a flexible assembly quote now.