Good design

If the circuit design is simple, the total size is not large, and there is enough space, most traditional interconnection methods are much cheaper. If the circuit is complex, processes many signals, or has special electrical or mechanical performance requirements, flexible circuits are better.

When the size and performance of the application exceed the capabilities of rigid circuits, flexible assembly methods are good. A flexible circuit with a 12mil pad, a 5mil through hole and a 3mil line and spacing can be made on a piece of film.

Therefore, direct chip mounting on films is reliable. There are no flame retardants that can be a source of ion drilling contamination. These films may be protective and cure at higher temperatures, resulting in higher glass transition temperatures. The reason why flexible materials save costs over rigid materials is that connectors are eliminated.

The high cost of raw materials is the main reason for the high price of FPC. The price of raw materials varies greatly. The cost of raw materials used in the lowest-cost polyester flexible circuit is 1.5 times that of raw materials used in rigid circuits. The cost of high-performance polyimide flexible circuits is as high as 4 times or more.

The flexibility of the material makes it difficult to automate processing during manufacturing, resulting in reduced yields. Defects are prone to occur during the final assembly process, such as peeling of flexible attachments.

This is more likely to happen when the design is not reasonable. Under high stress caused by bending or forming, it is often necessary to choose reinforcing or strengthening materials. Although the cost of raw material is high, and manufacturing is troublesome, the foldable, bendable and multi-layer boards can reduce the overall component size, reduce the material used, and reduce the total assembly cost.

The polymer thick film method is a kind of efficient and low-cost production process. It selectively screen-prints conductive polymer ink on an inexpensive flexible substrate. The representative material is PET. The conductor of the polymer thick film method is screen-printed metal filler or carbon powder filler.

The polymer thick film method is very clean. It uses lead-free SMT adhesives, and does not require etching. This method uses an additive process, and has a low substrate cost. The price of the circuit is 1/10 of that of a copper polyimide film circuit, and 1/2 to 1/3 of that of a rigid circuit board.

The polymer thick film method is particularly suitable for control panel of equipment. It saves costs and reduces energy consumption.

Generally speaking, FPC is indeed more expensive than rigid circuit. When producing flexible PCB, many parameters are out of tolerance. The difficulty lies in flexibility of the material.

Cost

The price of FPC assembly is now falling. The main reasons are the introduction of newer materials, improved production processes and changed structures. The structure makes the product more thermally stable, and there are fewer material mismatches. Some new materials can produce more precise lines due to thinner copper layers, making the components lighter and more suitable for installation in small spaces.

In the past, copper foil was adhered to the medium coated with adhesive by rolling process. Now, copper foil can be directly produced on the medium without using adhesive. We can produce copper layers several microns thick. Solder masks and other surface coatings have further reduced the cost of assembly.

In the next few years, smaller, more complex and more expensive FPC will require more innovative assembly methods and more hybrid flexible circuits. The challenge for the industry is to keep pace with computers, telecommunications, consumer demand and active markets. In addition, FPC will play an important role in the lead-free movement.