Information about the specifications:
Copper:
The base copper is chosen according to the difficulty of the structures. The copper deposit of plated flexible circuits (FPC) may also differ according to the structures. In general: The thinner the structures, the thinner the copper. Usually, the copper thickness will be around:
1-layer: 18µm or 35µm (depending on structures)
2-layer: 28µm
Solder Mask:
For most flexible circuits (FPC) either cover lay or wet solder mask can be used. Due to better bending performence and stability, cover lay will be preferred. However, when very small SMD structures have to be solder mask free this cover lay cannot be used. Then wet solder mask is used. The color is usuall yellow for cover lay and for solder mask, sometimes green wet solder mask is used. If only some SMD areas have to be solder mask free, cover lay is drilled at the SMD areas, thus have a round solder mask clearance instead of a reactangular one. Rectangular cover lay free areas are only possible for bigger areas as for connector areas. The solder mask layer in the Gerber files you provide are only used for reference. Small vias are always covered with solder mask. The type of solder mask - if not specified by you and feasable - will be chosen by LeitOn. This will also influence the total FPC thickness.
Total FPC thickness:
The total thickness of the FPC changes according to the solder mask type and the copper whickness. This, a general thickness cannot be released in advance. The thickness lies in between the following ranges:
Total thickness 1-layer: 0,06 to 0,13mm (depends on solder mask type and structures)
Total thickness 2-layer: 0,08 to 0,25mm (depends on solder mask type and structures)
Stiffener:
If stiffeners are selected, those will be made of polyimid and have a final FPC thickness of around 0,3mm for standard connectors. Other stiffener thickesses are available if stated in the comments field. If a further surcharge is applicable depends on the thickness of the stiffeners and the quantity. In general maximum two FR4 stiffener of a thickness between 0,3mm and 1,0mm can be considered being included. More or thicker stiffeners may lead to an additional surcharge. We will inform you about this after reviewing your files.
In case you do have specific requirements for the stack-up, copper thickness and solder mask please specify them in the comments field. We will check the feasability and contact you in case of non-conformity. If there are no specifications mentioned, the choice for the above mentioned characteristics lies at LeitOn only.
We hope you understand that due to the complexity of FPC these characteristics have to be left open upon confirmation. If you have any questions, please do not hesitate to contact us at any time.
