Single Sided PCB/Single Layer PCB

Single sided PCB definition

Single sided PCB ’s earliest industrial application can be traced back to the early 1950s. Because of its simple design principle and manufacturing process, it occupies an important position in the history of PCB manufacturing. Single sided PCB is covered with copper on one side only, with components distributed on one side and circuits distributed on the other side. From top to bottom, single panel usually consists of soldermask layer, copper layer and insulating material in turn.

Manufacturing process of single side PCB

Compared with other types of PCB, the manufacturing process of single sided PCB is simpler and the cost is lower in most cases. Generally, the main process is cutting-drilling-circuit treatment-etching -AOI- solder resist-text printing-forming-electrical measurement-surface treatment (OSP)- final inspection. In addition, more and more manufacturers now choose the manufacturing process of drilling holes before forming.

Features of Single sided PCB

As only one side of single sided PCB can distribute circuits, and the two sides can't be connected, compared with other PCBs, they need a larger area to carry the same number of components, so they are more suitable for the design with lower requirements for component distribution density.

Although single layer PCB design is simpler than other types of PCB, based on the characteristics of single-sided distribution, it has stricter specifications for the design of wiring and component positions. For example, the pad of single sided PCB must be large, otherwise it is easy to cause problems during welding and repair. The wiring of the circuit board can not cross, but can only be designed along their own paths, etc.

Main applications of single sided PCB

At present, the terminal products using single sided PCB mainly include calculators, charging products, LED lamp boards, FM radio, timers, etc. At the same time, according to different technology types, it can be divided into single-sided hard board, flexible single board, soft-hard combined single board and single-sided aluminum substrate.

Advantages and disadvantages of single sided PCB

Advantages of single sided PCB:

1. The single sided PCB needs less raw materials and the price is lower; The production process is less, and the overall production time is shorter;

2. The design and composition of the line are relatively simple, so the design can be completed without very rich professional experience;

3. Because of the simple process, for a large number of orders, the larger the order quantity, the more favorable the price.

On the other hand, compared with the double side PCB or multilayer PCB of the same size, the single side PCB board's shortcomings also constantly limit its development:

1. The limitation of single-side area can't meet the demand of installing a large number of components and more wiring;

2. And if it carries too many components, it may cause the problem of slow connection speed and power loss, so the applied product field is very limited.

On the whole, the application scenarios of single sided PCB are decreasing with the increasing technical requirements of producers, but it is still one of the best solutions for those who pursue speed and low cost.

Double sided PCB/Double layer PCB

Double sided PCB board characteristics

The difference between single sided PCB board and double sided PCB board is that the number of copper layers is different. Double sided PCB board is a circuit board with copper on both sides, which can be connected through vias. There is only a layer of copper on one side, which can only be used as a simple circuit, and the holes made can only be used for plug-ins that cannot be conducted.

The technical requirements of double sided PCB board are that the wiring density becomes larger, the aperture becomes smaller, and the aperture of metallized holes becomes smaller and smaller. The quality of metallization holes which are connected with each other directly affects the reliability of printed boards.

With the reduction of the hole diameter, once the impurities that have no influence on the larger hole diameter, such as grinding brush debris and volcanic ash, remain in the small hole, the chemical copper deposition and electroplating will lose their effect, and the hole without copper will become the fatal killer of hole metallization.

Double layer PCB board has wiring on both sides, but to use wires on both sides, it is necessary to have proper circuit connections between the two sides. This "bridge" between circuits is called a via. A via hole is a small hole filled or coated with metal on the PCB board, which can be connected with the wires on both sides. When drawing a double sided PCB board with PROTEL, draw wires on the TopLayer to connect components, that is, draw the board on the top layer; Select the BottomLayer and draw wires on the bottom layer to connect components, that is, draw a board on the bottom layer. The above is to draw a double sided PCB board, which means drawing wires on the top and bottom layers of a PCB board. Double sided PCB board solves the difficulty of single-panel because of staggered wiring (it can be connected to the other side through holes), that is, both front and back sides have wiring, and components can be welded on the front side or the back side, so it is more suitable for use in more complicated circuits than single sided PCB board.

Strictly speaking, double sided PCB board is an important kind of PCB in circuit boards, and its use is very large. It is also very simple to see whether a PCB board is double sided PCB. I believe that friends can fully grasp the understanding of single panel. Double sided PCB board is the extension of single sided PCB board, which means that the circuit of single sided PCB board is not enough to turn to the opposite side. Double sided PCB board also has an important feature of via holes. Simply put, it is double-sided wiring, and there are lines on both sides! In a word, a double-sided wiring is a double-sided board! Some friends are going to ask, for example, a board with double-sided wiring, but only one side has electronic components. Is this board a double-sided PCB board or a single sided PCB board? The answer is obvious, such a board is double sided PCB board, only the components are installed on the board of double sided PCB board.

Welding method of double sided PCB board

In order to ensure the reliable conductive effect of double-sided circuit, the connecting hole (i.e. the through hole part of metallization process) on the double sided PCB board should be welded with wires at first, and the protruding part of the connecting wire tip should be cut off to avoid stabbing the operator's hand. This is the preparation work for connecting the board.

Single sided PCB vs double sided

The difference between double sided PCB board and single sided PCB board lies in that the single sided PCB board is only on one side of the PCB board, while the double sided PCB board can be placed in both sides of the PCB board, and a hole is used in the middle to connect the double-sided PCB circuit.

Parameters of Double sided PCB board, the manufacturing process of double sided PCB board is different from that of single sided PCB board, and there is also a copper deposition process, that is, the process of conducting double-sided circuits.

Single sided flex PCB

Single sided flex PCB, with only one layer of conductor, can be covered or uncovered on the surface. The insulating base material used varies with the application of the product. Commonly used insulating materials are polyester, polyimide, polytetrafluoroethylene and soft epoxy-glass cloth. 　　 

Single sided flex PCB can be further divided into the following four categories:

1) Single-sided connection without covering layer

The conductor pattern of this kind of single sided flex PCB is on the insulating substrate, and there is no covering layer on the conductor surface. Like a common single sided rigid PCB. This kind of product is the cheapest one, usually used in non-critical and environmentally friendly applications.  

The interconnection is realized by soldering, welding or pressure welding. It is often used in early telephones. 　 

2) One-sided connection with covering layer

Compared with the former class, this class only adds a layer of covering layer on the conductor surface according to the customer's requirements. When covering, the bonding pad should be exposed, and it can be simply left uncovered in the end area. If required, clearance holes can be used. It is one of the most widely used single sided flex PCB, and is widely used in automobile instruments and electronic instruments.  

3) Double-sided connection without covering layer

This kind of connection pad interface can be connected on the front and back of the wire. For this purpose, a via hole is made in the insulating substrate at the pad, which can be punched, etched or made by other mechanical methods at the desired position of the insulating substrate. It is used for mounting components and devices on both sides and for occasions needing soldering. There is no insulating substrate in the pad area at the via, and such pad area is usually removed by chemical methods.  

4) Two-sided connection with covering layer

This class is different from the former class in that there is a covering layer on the surface. However, the cover layer has a via hole, which also allows both sides of the cover layer to be terminated, and still maintains the cover layer. This kind of single sided flex PCB is made of two layers of insulating materials and one layer of metal conductor.  

It is used in situations where the covering layer needs to be insulated from the surrounding devices, and itself needs to be insulated from each other, and the front and back sides of the ends need to be connected.