Looking for a flexible PCB but find the polyimide alternative more expensive?
Then look at the SEMI-FLEX solution from Eurocircuits and see if that is your way. In this month's Review, we take a closer look at the features of this service.
With the SEMI-FLEX Pool, you can achieve a remarkable production process in Eurocircuits. The product is exactly what it is called: a flexible PCB. A little flexibility means you can bend the circuit board a few times, usually five times, before it creates a problem. This is ideal for products where different circuit boards are fitted with different angles, and there is no need for continuous flexibility. The regional board only needs to be folded into the desired position, and, at the time of consolidation, it is no longer flexible.
Working with a flexible circuit board has the advantage that no weak (fence) connections are required. The connectors can oxidize and do not interact properly after some time, which compromises the safety and reliability of the product. By reducing the number of connectors, the number of solder joints decreases, which also positively affects reliability. It simplifies the manufacturing process: no need to make special interconnect cable wires and install them by hand. The SEMI-FLEX Pool from Eurocircuits does not use expensive polyimide material but instead uses a thin layer of 'standard' FR4. This layer is made of laminated on both sides with a layer of copper. An asset does not receive special handling to be folded several times without breaking it. The flexible circuit board comprises four available copper layers, in which the flexible part contains only the 'core' - a thin FR4 layer with a copper layer on both sides. Therefore, the flexible connection between the two circuit boards is not four layers but two layers. The angle and radius the board is allowed to perform are defined.
The SEMI-FLEX Pool offers high reliability with a few thin connectors and cable wires and a few solder joints.
It takes less time to compile
The SEMI-FLEX Pool uses FR4 material, which is more affordable than polyimide.
The main central layer of the SEMI-FLEX Pool consists of a thin 100 µm layer of FR4, with both sides a 35 µm thick layer of copper foil. This is how the flexible part is integrated. With this flexible part in the middle, circuit boards continue to build on this backbone, so it continues throughout the circuit board. In the two inner layers comes a double pre-preg layer with a total thickness of 126 µm. This is followed by a 0.51 mm thick layer of FR4 material with an 18 µm thick copper foil. These outer layers are processed the same way as the four standard '4' regional circuit boards. The picture shows this meeting. This symmetrical structure results from instability and stability
When laying out the circuit board, the designer needs to look at the following features of the SEMI-FLEX Pool:
The minimum bending radius is 5 mm
The maximum angle of inclination is 180 °
To determine the required length of the SEMI-FLEX section, using the following formula:
2 × pi × radius × (angle / 360),
For example, with a radius of 5 mm and an angle of 180 °: 2 × pi × five × 180/360 = 15.7 mm.
The copper thickness of the semi-flex section is 35 µm
In the semi-flex section, no holes, gaps or cut-outs are allowed
The minimum angle of inclination of the semi-flex section is 1.00 mm
It is best to arrange the copper on both sides of the slightly flexible part and surround the print tracks with a polygon.
The final ending of the fixed part requires selecting Che Ni / Au (ENIG)
The solder mask is green
Screen printing, spaces and cuts are similar to the JINGA amendment.
Advanced production methods allowed by compacting mask, PTH edge of the board, circular plate, brass to the edge. Carbon pads and a gold edge connector are available in the non-binding options.
UL-marking is not yet available.
Due to its durability, it is best to supply the PCB to the panel.
Ordering a regional board using the SEMI-FLEX Pool is the same as ordering a board using other services from Eurocircuits. Here again, you can access a wide range of features of PCB Visualizer, PCB Checker and direct help from an experienced technical member from the Eurocircuits team. (see also our Review of STANDARD pool, RF pool or IMS pool).