FPC Manufacturing Process

  • 01. Material Releasing
  • 02. Drilling
  • 03. Plating
  • 04. Trace
  • 05. Coverlay
  • 06. Silkscreen
  • 07. Surface Finish
  • 08. Punch
  • 09. Test
  • 10. Assembly
  • 11. FQC

Choose the correct thickness and size of raw materials according to the production specifications.

FPC, also known as Flexible Circuit board, incorporates PI as its base material. This circuit board has the characteristics of lightweight, thin thickness and good bending flexibility... and so on. The basic structure of FPC is comprised of the following parts:
● Coverlay
● Copper layer
● Polyimide (PI)
● Stiffener - not essential, common materials are like PI, SUS, FR-4.
**The above structures are glued together by an adhesive.**

Use CNC drilling machine to drill holes, which for connecting conductor from layer to layer and mounting components.

 Processing holes such as parts holes, fixed holes, and via holes according customer’s design, and provide positioning holes required for subsequent processes. The drilling machine is computer-controlled. The operator set up the drill program. High speed drilling ensures clean hole walls to provide a secure base for good plating on the hole walls.

 Drilling is a slow process as each hole must be drilled individually. We can drill holes down to 8 mil in diameter. Drill change is fully automatic. The machine selects the correct drill to use from the drill rack, and then loads it into the drill head.

Copper plating is carried out in the hole to realize layer-to-layer wiring connection.

 Removing the glue residue left on the hole wall after drilling, plate copper on the hole-wall to realize pattern connection between layers, the copper surface is thickened by electroplating to meet the customer and subsequent process requirements.

Make wire traces on the outer layer of the copper-plated board.

 Cover the surface of the board with a layer of organic film that is optically active, and after exposure, transfer the pattern of the outer film to the board surface. And thicken the outer layer circuit by second electroplating.

Attach an insulating layer called "Coverlay" onto FPC to protect the copper surface.

 The coverlay consists of a sheet of polyimide with a layer of adhesive. Coverlay plays the same role as a soldermask on Rigid PCB. The coverlay is usually supplied in roll form and be cut to fit the FPC size.

Print the necessary information onto the PCB surface with non-conductive epoxy ink.

 Silkscreen will be conducted If customer requests to print the visible information like logos, part number and component markings onto the boards.

Improve the solderability and protect the area without solder mask from oxidation, which may influence the stability.

 To protect the copper solder pads on a PCB from oxidation, contamination and to enhance their solderability, they need to be protected with a Surface Finish.

ExPlus offers the following Surface Finishes:
 ● Hot Air Solder Levelling ( HASL / Lead-Free HASL)
 ● Immersion Gold (ENIG)
 ● Electroplated Ni/Au (Hard Gold) for Edge Connectors
 ● Carbon for Switch Contacts
 ● Organic Solderability Preservative (OSP)
 ● Immersion Silver

Use both laser cutting and punch die methods to make FPC outline.

 There are several different methods for processing outline of flexible PCB, including hand trim, steel rule die, punching die, and laser cutting. Generally we use Punching Die and Laser Cutting to make FPC outline. We use laser cutting for low volume and prototypes, and punching die for bulk production.

Conduct electrical tests and other necessary tests to ensure the quality of the circuit board.

ExPlus conducts 100% electrical tests on circuit boards before shipping to the costumer. We also provide Hipot test to meet the requirement of customers. Our PCB test systems include:
The flying probe testers, which are suitable for testing small batches and highly complex PCBs.
Universal grid testers, which require the use of a separate test fixture, are well suited for testing bulk-manufactured PCBs.

Reinforce FPC with materials required by customers.

 If the FPC needs stiffener for reinforcement, this is where the process takes place. The stiffener is attached to the back of the FPC when a widget such as a connector is attached to the FPC. The common stiffener materials are PI, FR-4 and stainless steel (SUS).

Conduct the final product inspection before the shipping.

 To achieve the goal of zero defects and zero complaints from customers. The finished product must be inspected before leaving the factory. Responsible for the quality control before the finished product is packed.