What is a single layer flex PCB?

A Single Layer Flex PCB has only one conductor, and the surface can have or have no covering. The insulating base material used varies with the application of the product. Commonly used insulating materials are polyester, polyimide, polytetrafluoroethylene, soft epoxy glass cloth. Single Layer Flex PCB are classified according to the structure of conductors as follows:

1) Single layer flex PCB with single side connection without overlay

This type of single layer flex PCB wire graphics on the insulating substrate, wire surface without covering layer. Single layer flex PCB are the lowest costly and are typically used in environmentally friendly applications.

2) Single layer flex PCB with cover layer single-side connection

Compared with the previous single layer flex PCB, this kind of single layer flex PCB only has an extra covering layer on the wire surface according to the customer's requirements, and the welding pad should be exposed when covering. When required, precision can be used in the form of clearance holes. It is the most widely used single layer flex PCB, and it is widely used in automobile instruments and electronic instruments.

3) Single layer flex PCB without overlay double-sided connection

The connecting disc interface of this type of single layer flex PCB can be connected on both the front and back of the conductor. To do this, a path hole is cut in the insulating substrate at the pad. The path hole can be first punched, etched or otherwise mechanically made at the desired position of the insulating substrate.

4) Single layer flex PCB with double-sided connection of covering layer

This single layer flex PCB differs from the previous single layer flex PCB in that the surface has a covering layer, but the covering layer has access holes which also allow both sides to be terminated and still maintain the covering layer. This single layer flex PCB is made of two layers of insulation and one layer of metal conductor.

Single Layer Flex PCB basic structure form

Single layer flex PCB are the most basic types of flexible circuits. They consist of a flexible dielectric film laminated to a single sheet of copper, which is then chemically etched into the copper layer according to a specified circuit pattern design. A single layer flex PCB consists of a single conductive copper layer that can be bonded between two insulating layers, or constructed from a polyimide insulating layer and uncovered sides, and then the inner copper layer goes through a chemical etching process to produce the circuit. Single layer flex PCB design supports components, connectors, pins and stiffeners.

Some single layer flex PCBs feature a two-channel design that facilitates access to conductive materials from both sides of the circuit in order to provide a channel for a single copper layer through the polyimide layer of the substrate. As a connection device, compared to traditional cables and rigid circuit boards, a single layer flex PCB includes:

• Reduce wiring errors

• Eliminate mechanical connectors

• Unmatched design flexibility

• Higher circuit density

• More powerful operating temperature range

• Stronger signal quality

• Improved reliability and impedance control

• Reduction in size and weight

Single layer flex PCB production process

PCB circuit board is the basic product of the electronic industry, widely used in communication equipment, computers, automotive electronics and industrial equipment and a variety of household appliances and other electronic products.  Its main function is to support circuit components and interconnect circuit components. FPC is a large category of printed circuit boards. According to the structure of FPC, according to the number of conductor layers can be divided into Single Layer Flex PCB, double panel, multi-layer board, to understand the Single Layer Flex PCB manufacturing process.

Sheets Cutting → Drilling → Sticking Dry Film → Alignment → Exposure → Developing → Etching → Removing Film → Surface Process → Sticking Covering Film → Pressing → Curing → Surface Treatment → Sinking Nickel Gold → Printing Characters → Cutting → Electrical Measurement → Punching → Final Inspection → Packaging → Shipping

Single Layer Flex PCB substrate film commonly used polyimide (PI), polyester (PET), PEN, liquid crystal polymer (LCP) and other polymer films.

Single Layer Flex PCB production problem?

In the production of Single Layer Flex PCB, the quality of the first product was confirmed to be OK, and the etching fluid and equipment were also verified to be OK. However, there was a problem in the production of the whole roll, and the line erosion did not open on the first sheet. What is the cause of this?

If it is a single chip test, Bath Loading is not extreme, but if it is used continuously, the potion will be exhausted, then the replenishment state must be accurately controlled;  if it is the general Single layer flex PCB continuous operation, liquid reflux condition and liquid supplement is not easy to control;  single layer flex PCB in operation is flat, liquid flow is smooth is also a critical consideration.

Single layer flex PCB can be operated with copper face down, which is not prone to water lag effect and uneven liquid flow problems, and may improve the corrosion of the line is not open. In addition, when making single layer flex PCB, developing and etching film stripping are separate, mainly for consideration of speed matching. The front section of etching had better be treated with water wetting, otherwise the line making of single layer flex PCB will be etched not open.

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