Similar to other circuit boards, the production of Flexible PCB is relatively straightforward. Furthermore, its process doesn’t differ that much from the other boards; however, one thing to note is the materials employed on them, it utilizes Flexible Polyimide that is Hydroscopic.
Along with that, Flexible PCB necessitates the pre-baking stage its time may vary according to the layers, stiffeners, and the particular construction method preferred.
Essentially, the estimation of this stage is approximately two to ten hours depending on the layer count. Hence, in this article, we’d like to touch on the step-by-step process of Flex PCB Production, Flex PCB Technology, Flexible PCB Basic Materials, Pre-Bake Specifications, and Certifications.
What is the Flex PCB Manufacturing Process?
As its term suggests, Flexible PCB Manufacturing is the production of a board with Flexible Substrates and Layers. Some of the advantages of incorporating a Flex Circuit in their applications are its inexpensive cost, compact size, and outstanding versatility.
In line with this, at MV Flex Circuit, we can modify our client’s desired Flexible Circuit depending on their purpose and application. Along with that, they are highly preferred in Medical, Industrial, Aerospace, Military, Automotive, and other devices.
DIY Production of Flexible PCB
Preparation of Material
As its name indicates, the Preparation of the Material phase includes the gathering and evaluation of constituents that will be incorporated in the production of the Flexible PCB.
Before applying the electromechanical photoresist film, fabrication panels are carefully cleansed to guarantee correct film adherence. Furthermore, extremely thin substance cores are protected by a conveyorized method that makes use of thin-core handling equipment.
Circuit Pattern Exposure
Simply put, in Circuit Pattern Exposure, the electronic architecture configurations are overlaid on photo-suppress-covered screens, which are then subjected to diffracted UV light to move the circuit images to manufacturing sheets. If necessary, all surfaces can be revealed at once.
Etch Process
Only with aid of conveyorized mechanisms with thin core handling equipment, circuit designs were electronically engraved. If necessary, all panel surfaces can be engraved at once.
Drilling Process
The necessary circuit hole designs are created in manufacturing panels by high speed, high accuracy, and tiny bit piercing devices. In terms of ultra-small opening needs, there are beam devices accessible.
Copper Plating Process
In order to create layer-to-layer electronic circuitry, fully automatic electrolytic copper coating devices place the necessary extra copper into gilded through perforations.
Incorporation of Coverlay
On manufacturing surfaces, Polyimide Coverlays are positioned, oriented, and fastened in position before the Coverlay encapsulation procedure.
Lamination of Coverlay
In order to guarantee appropriate bonding, Coverlays are fused to manufacturing surfaces under compression, pressure, and suction.
Integration of Stiffener
Even before a further layering procedure under tension, pressure, and suction, discrete extra reinforcement according to the configuration is positioned and affixed.
Electrical Inspection
In essence, an electrical evaluation that is entirely based on netlists, as per IPC-ET 652. Moreover, checking for separation and continuity simultaneously on all wires. Ultimately, monitoring devices that use all array and floating probes are used.
Final Process
At the final stage, specific components are machine-made with high-accuracy male and female punches as well as die kits from manufacturing panels. According to the requirements of the architecture, additional techniques encompass laser cutting, pneumatic drafting, ferrous principle dies, and electronically machined dies.
Flexible PCB Technology
One of the extreme advantages of the Flexible PCB is its versatility and reliability. Hence, they are highly essential in electronics that necessitate good bendability. In line with this, the Flexible PCB are classified into three (3) fundamental technologies depending on their quality.
Partial Flex
As its term indicates, the Partial Flex Circuitry has restricted versatile capabilities. Since their primary structure is rather unyielding than those of other kinds, Partial Flex Circuits can curve or rotate without fracturing. In addition, low-flex boards, like connections with PCBs on them, require this kind of circuitry to operate effectively.
Full Flex
In comparison with Partial Flex Circuitry, Full Flex Circuitry has almost a versatile structure in all aspects of the panel. In essence, a Full Flex PCB has all of its segments placed on the surface of one another with only a minuscule quantity of mobility for the bendable circuitry located there. Such circuitry works well with emitters and receptors because they never move from their starting positions.
Hybrid Flex
As its name suggests, the Hybrid Flex Circuitry is the junction of Rigid and Flexible Substrates to produce an efficiently performing output. In addition, its responsibility is quite similar to the Rigid PCBs.
Fundamental Material of Flexible PCB
Simply put, the quality and performance of Flexible and Rigid-Flex PCBs rely on their Substrate Materials. Hence, in this section, we’ll dissect each of the substrate materials preferred in such productions; we have Polyester, Polyimide, and Polytetrafluoroethylene.
Performance Item | Polyester | Polyimide | Polytetrafluoroethylene |
Limit Tension | 172 N/mm-2 | 172 N/mm-2 | 20.7 N/mm-2 |
| Limit Elongation | 120% | 70% | 300% |
After Etching Dimensions | 5 mm/m-1 | 2.5 mm/m-1 | 5 mm/m-1 |
| Relative Dielectric Constant | 3.2 103 Hz | 3.5 103 Hz | 22.1 103 Hz |
Loss Angle Tangent | 0.005 103 Hz | 0.0025 103 Hz | 0.0001 103 Hz |
| Volume Resistance | 1,012 MΩ/cm-1 | 1,012 MΩ/cm-1 | 1,012 MΩ/cm-1 |
Flammability | Flammable | Self-Extinguishing | Inflammable |
| Dielectric Strength | 300 mV/m | 275 mV/m | 17 mV/m |
Moisture Absorption | < 0.8% | 2.7% | 0.01% |
| Heat Resistance | 150°C | 400°C | 260°C |
| Soldering Inspection | Pass | Pass | Pass |
Flexible PCB Assembly Pre-Bake Specifications
As mentioned, Flexible PCB Assembly necessitates the conduction of Pre-Bake Action similar to other PCBs to eliminate the presence of moisture that may potentially harm the board since Flexible Polyimide Materials are Hygroscopic. Notwithstanding the producer or model of polyimide substances selected, this is a characteristic of the composites that exists inherently.
Standard Pre-Bake Specifications for Flexible PCB
According to the standard guidelines, it is highly essential to subject any circuit boards to the Pre-Baking Stage before its assembly of it without any restrictions. In case the product arrived with a full vacuum-sealed package, it is still recommended to Pre-Bake them as part of the rules.
Furthermore, if that product was baked before handing it over to the manufacturer, this doesn’t make an exemption of not Pre-Baking it before the construction phase.
All of these are strictly performed to ensure that there will be no occurrences of the coverlay, layer, and stiffener delamination. Since if the wetness or dampness won’t be eradicated, these issues may arise. The construction reflow conditions, which are the main contributor, transform the confined wetness into vapor. This same deformation is caused by the steam’s growth.
Therefore, the experts suggest that every Flexible PCB must be subjected to a hundred and twenty-degree Celsius (120°C) of Pre-Baking. However, as stated earlier, it may still change depending on countless factors. In terms of duration, it can run from two hours up to ten hours.
Flexible PCB Certifications
Before we deliver the Flexible PCB to our consumers, we always ensure that they abide by the different certifications required in Flex Circuitry. We have gathered all of the IPC Certifications needed to attain the highest possible performing Flexible Circuit in the market.
Different IPC Accreditations for Quality Flexible PCB
Materials of Flexible PCB
- IPC 4202 – Basic Dielectrics with Adaptability.
- IPC 4203 – Glue-Coated Dielectric Sheets.
- IPC 4204 – Adjustable Dielectrics with Metal Cladding.
Performance of Flexible PCB
- IPC 6011 – Standard Performance Criteria for Laminated Circuits.
- IPC 6012 – Efficiency and Certification for Robust Circuit Boards.
- IPC 6013 – Efficiency and Certification for Versatile Circuit Boards.
Flexible PCB Design Architecture
- IPC FC 2221 – Specification for Printed Circuit Board Architecture in Particular.
- IPC FC 2222 – Rigid PCBs.
- IPC FC 2223 – Flexible PCBs.
Quality Guidelines for Flexible PCB
- IPC A 600 – Laminated Boards’ Suitability.
- IPC A 610 – Laminated Board Structures’ Compatibility.
- IPC J STD001 – Tensioned Electrical and Computer Assembly Standards.
Summary
In summary, we have covered the fundamental stages that a Flexible PCB undergoes; starting from the procurement of the materials and components, until the inspection, packaging, and delivery of the products. Also, we have touched the vital information related to the production of Flexible PCBs.
If you have any inquiries regarding our offers for Flexible PCBs, do not hesitate to reach out at MV Flex Circuit. We are highly capable of producing your desired Flexible Circuit Boards at their exceptional quality and performance possible through the help of our over 15 years of extensive industry experience, skilled and seasoned personnel, and sophisticated technologies.
Why are you holding back? By giving us a quote, you can start enjoying your high-performing flexible PCB with us right away. We promise to address your concerns as soon as possible because we have professionals waiting to sort out these problems on your behalf. Come and partner with us!
