Introduction to A Flexible Circuit Coverlay

During the flexible printed circuit board manufacturing process, a flex circuit coverlay (aka coverfilm) is used to encapsulate and protect the external circuitry of a flexible circuit board.
flexible circuit coverlay serves the exact same function as solder mask that is used on a rigid printed circuit board. The difference with a flex coverlay is the needed element of flexibility and durability it provides to the flex PCB design.
The coverlay consists of a solid sheet of polyimide with a layer of flexible adhesive that is then laminated under heat and pressurized to the circuit surfaces. The required component feature openings are mechanically created using drilling, routing, or laser cutting.
Typical coverlay thickness is 0.001″ polyimide with 0.001″ of adhesive. Thicknesses of 0.0005″ & 0.002″ are available, but only used as needed to meet specific design requirements.
For more information visit our website to learn more about our flex & rigid-flex PCB manufacturing process!

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How to Paste Coverlay on FPC?

If you have ever learned something about flex circuits, you would know there is a layer of coverlay on it. Pasting coverlay on flexible circuit is to prevent it from the damages of dust, moisture and so on. Meanwhile, it also plays an role in insulation. We have learned something about the benefits of pasting coverlay on flex circuits, but how to paste the coverlay? Let’s take a look.
To begin with, we need to prepare the coverlay material, checking whether the soldering iron has power, cleaning the residue of soldering iron and the dust-free paper.

The procedures of pasting the coverlay on FPC:

  1. Checking whether the coverlay and film have problems, including missing punching, missing drilling, too large burr on the coverlay etc.. After that, clean the dust on the surface of coverlay with packaging cleaner.
  2. Cleaning the worktable and putting the coverlay, soldering iron and other tools in the right place.
  3. Checking whether there are oxidization, litter, dust etc. on the flex circuits to be pasted.
  4. Pasting the coverlay should follow the requirements of process and the MI data. It should be strictly follow the “C”marking line, pad or counterpoint hole when align.
  5. How to peel the coverlay off: putting the covelay on the optical desk, but please remember that the release film is facing up and the coverlay is facing down. After that, holding the coverlay then peeling off the release film slowly.
peeling the coverlay off

peeling the coverlay off

  1. Fixing the coverlay on FPCwith soldering iron after the coverlay is aligned with the “C” marking line of the flex circuit board and ensure it is correct, so that the coverlay can not deviate or peel off. However, please remember the soldering iron can not burn the products.
pasting coverlay on FPC

pasting coverlay on FPC

  1. Single-side lamination: after pasted the coverlay on FPC, it should be gone through the machine with temperature between 160°C-165°C. Next, until the board got cold, the release film should be peel off and carry out the single-side lamination and self-checking.

Notices:
1. It is necessary to wear rubber gloves to prevent the flexible printed circuit board from oxidization or dirty.

  1. It must be kept clean during pasting coverlay on FPCto prevent there are dirty residues on flex circuits.
  2. It is required to check whether the coverlay is broken, wrinkled, scratched, etc..
  3. Do not wear accessories to avoid scratching the board.
  4. It is necessary to confirm that the coverlay leave a little bit space for plating if the flex circuitsare tin or gold plating.
  5. The hand could not beyond the handle to avoid burning when holding the soldering iron.

Best Technology is the premier expert in the manufacture of electronic components, brings a unique combination of technology and quality that offers a competitive supply of flex circuits and rigid-flex circuits and other flexible circuit products. With high qualified engineers, we are able to help you find a FPC with high quality. To find out more, contact Best Technology at 0755-29091601 or check the website: https://www.bestfpc.com

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