According to the placement accuracy requirements and components of the different types and quantities, the current commonly used flexible PCB assembly solutions are as follows:
Option 1, simple mounting on a single side FPC
- Scope of application
- Component types: mainly resistors and capacitors, etc.
- Components quantity: Each piece of FPC need to mount a small number of components, generally only a few components.
- placement accuracy: placement accuracy is not high (only chip components).
- FPC characteristics: a small area.
- Bulk: generally are in million units of measurement.
- Manufacturing process
- Solder paste printing: FPC positioning in the printing on the special pallet, the general use of small semi-automatic special printing presses. Subject to conditions, you can also use manual printing, but the printing quality is unstable, the effect is worse than semi-automatic printing.
- Mounting: General can be manually mounted. Individual components with slightly higher position requirements can also be mounted using a manual placement machine.
- Flexible pcb soldering: generally use reflow soldering process. Special circumstances can also be used special equipment spot welding. If the manual welding, the quality is difficult to control.
2, multi-chip placement: multi-chip positioning by positioning template FPC half on the care, and the whole fixed in the bracket with the SMT placement.
- Scope of application:
A, component types: chip components are generally larger than 0603, pin spacing greater than or equal to 0.65 of the QFQ and other components can be.
B, the number of components: each FPC on several components to a dozen components.
C, placement accuracy: placement accuracy requirements medium.
D, FPC characteristics: the area is slightly larger, there is no region in the appropriate components, each FPC has two markers for the optical positioning MARK and more than two positioning holes.
- Fixation of FPC:
According to the CAD data of the metal pad, the internal positioning data of the FPC is read to produce a high-precision FPC positioning template. So that the diameter of the positioning pin on the template and FPC hole positioning holes to match, and the height of about 2.5mm. FPC positioning template there are two under the pallet pin. A number of pallets are manufactured from the same CAD data. Pallet thickness of about 2mm as well, and the material after several thermal shock after warping deformation is small, with good FR-4 materials and other high-quality materials is better. Prior to flexible pcb smt, first place the pallet on the pallet locating pin on the template to expose the positioning pin through the hole in the pallet. FPC will be set in a set of exposed pin, with a thin high-temperature tape fixed on the pallet, not to offset the FPC, and then leave the pallet and FPC positioning template separation, welding printing and placement, high temperature Tape (PA protective film) pressure to moderate, after high temperature impact must be easy to peel. And there is no residual glue on the FPC.
It is important to note that the shorter the time between FPC mounting on the pallet and the time between soldering and mounting, the better.