How to fabricate Semi-Flexible FR4 Printed Circuit Board?

How to fabricate Semi-Flexible FR4 Printed Circuit Board

 

Due to development of electronic products in every era of life till getting the small size ones, Printed Circuit boards of type flex rigid ones have got many types of uses. The most interest of people’s industry in flex rigid printed circuit boards fabrication technology is due to dictatorial increased competition in the market. Some printed circuit board makers who specialize in the fabrication process of flex rigid printed circuit boards don’t get to succeed because of complex and difficult process of this type of printed circuit boards. In this article, a kind of printed circuit boards like FR4 semi-flex Printed circuit board will be instigated which quirk in pliability, three-dimensional manufacturing and suppleness.

 

FR4 Semi-flex Printed Circuit boards Attributes:

 

1. Pliability, assembling in three-dimensional and the shape alteration in accordance to the limit of space available.

 

2. It is Flexible without any interruption in transmission of signals.

 

3. Plant labor who do the assembling or the errors in the printed circuit board can be minimized while refining the life span of electronic products based on the electronic product getting designed.

 

4. Shrinking in the volume of PCB, due to which PCB size is minimized, increased functionality and cost reduction.

 

5. Its process of fabrication is in tune with the makers of rigid printed circuit boards.

 

Process of Fabrication:

 

6-layer PCB is processed through mechanical assembling a milling groove for fabrication by applying filler as substrate and the filler is contained in FR4 mid targeted material. The rest of thickness of the PCB is adjusted within the 0. 25mm±0.25mm range. Due to this, FR4 Semi-flex PCB should be compatible bending over 900 while no cracks occurring in it for more than 10 times. This process includes the following steps to reach out to the final goal:

 

1. Cutting of the material

2. Coating of Dry film

3. Automated Optical Inspection

4. Brownization

5. Lamination

6. Inspection by X-rays

7. Drilling of holes

8. Electroplating

9. Conversion of graphics

10. Etching

11. Silk-screen Printing

12. Manifestation and development

13. Finishing of the surfaces

14. Milling using depth-controlled process

15. Electrical test

16. Final Quality Control Test

17. Packaging of the product

 

Problems and their respective Solutions during process of Fabrication:

 

The main problem in the process of fabrication is the controlling accuracy and deep controlled milling tolerance. Rigid Printed Circuit Boards characterize in sufficient pliability till the perfect performance after assembling in three-dimensional without any cracks or peeling of oil which are the prospective quality risks because of material’s properties and structure. Due to which during the deep controlled milling process, the uniform thickness of the board, tolerance of milling and contents of resin must be bring to full consideration and the final thing which is the range of optimal remained thickness should be defined properly.

 

  • Test A of Deep Controlled Milling

 

The rest of the milling thickness is brought out by the method of mapping and is attained in respective manner of the rest of the thickness of 0.25mm, 0.275mm and 0.3mm and after that process, the board is tested out in terms of 900 pliability. But rest of the thickness of size 0.275mm and 0.3mm does not get to meet our demands. This happens because of failure of the board’s flexibility within the bundle damage of fiber glass. This happens when the thickness approaches to 0.283mm level, fiber glass is damaged till then. Due to this, considering the thickness of fiber glass and situation of dielectric deep controlled milling should be carried out in accordance with the thickness of the board. Hence, the thickness is within the range of 0.188mm-0.213mm between L2-copper plane and oil surfaced solder mask, the requirement of board’s reliability will be failed when rest of the board’s thickness is more than 0.275mm.

 

  • Test B of Deep Controlled Milling

 

Copper’s Dielectric Thickness between L2-copper plane and solder mask lies within range of 0.188mm-0.213mm and pliability of 900 gets to be failed when the rest of the board’s thickness gets above 0.2833mm which is based on the test above performed and microsection analysis. Hence, mechanical process of manufacturing can be processed when the rest of the board’s thickness tolerance within the range of 0.245mm±0.213mm gets to be controlled. This needs to be done because the size of the panels is much larger due to thickness of the board and warpage in the process of mapping gets to be failed by matching. Due to which, the uniform remaining thickness of the board gets to be decreased.

 

  • Test C of Deep Controlled Milling

 

The forward effect appears to the uniformity of the machine and warpage of the board due to shrinking in the volumetric size of the board. First, the prototyping of the panel is done and then the deep controlled milling is done with respect to the size of 6.3”x10.5”. After that, measurement of mapping point with respect to interval of 20mm horizontal and vertical plane is measured for the uniformity of the machine.

 

A special type of fabrication method is carried out and developed out in a mechanical manner to deep control and keep going with the rest of the thickness. Due to this, the process of fabrication is simplified. The other processes stick to the primary parameters. And hence, the tolerance of the rest of the deep controlled thickness gets to be prolonged which lies in the range of ±20μm.

 

  • Semi-Flex Printed Circuit Boards are manufactured by RayPCB

 

Experience in the manufacturing of semi-flex printed circuit boards is much rich by RayPCB. If you have got the similar need, then do not step out and reach us to www.raypcb.com for the discussion of your projects. The contribution of the solution of the manner of cost-effective and practical will be provided as soon upon discussion.