Talking about the soldering layer of PCB.

What is the soldering layer of PCB.

PCB solder mask is an indispensable component of modern electronic equipment. As a support platform for electronic components, it realizes the functions of electronic equipment by connecting circuits. In the PCBA processing process, welding is an important process. In order to improve welding quality and efficiency, PCB soldering flux layers are widely used.

1.The role of PCB soldering layer

PCB flux layer is a special material layer covered on the PCB to provide the characteristics and environment required for the soldering process. It has two main functions: one is to protect the PCB surface from oxidation and contamination, and the other is to provide the heat conduction and wetting properties required during soldering.

2. Types of PCB soldering flux layers

Common ones include Solder Mask and Solder Resist. Solder paste is a green, red or other colored film that covers the PCB pads. It is mainly used to protect the copper layer on the PCB to prevent oxidation and contamination. It can also isolate adjacent pads to avoid short circuit problems. Solder mask is a layer of material that covers between PCB components and pads. It is usually black or other colors and is used to cover areas on the PCB that do not need to be soldered to prevent short circuits and soldering errors. In addition to solder paste and solder mask, there are other soldering flux materials, such as conductive carbon ink and thermal interface material, which play an important role in specific soldering applications.

3. Application of PCB soldering flux layer

First of all, during the PCB manufacturing process, the soldering flux layer can provide protection and isolation functions to prevent oxidation, corrosion, short circuits and other problems. This helps improve PCB reliability and stability. Secondly, solder paste can improve the efficiency and quality of soldering. It can help welding workers place solder accurately and provide good wetting properties, making the contact between the pad and the component stronger. In addition, the soldering flux layer can also provide thermal conductivity properties to help radiators and heat dissipation components better dissipate heat and maintain the normal operating temperature of electronic equipment.

4. In PCB design, the importance of correctly selecting and using soldering flux layer

First, the appropriate flux material and color need to be selected based on the specific application requirements. Different soldering flux layers have different requirements for different welding processes and environments. Secondly, the design and layout of the soldering flux layer need to consider the position and spacing of various components and pads on the PCB to avoid short circuits and soldering errors. In addition, solder paste coating uniformity and thickness control are also important factors affecting welding quality.


The difference between PCB solder mask layer and solder flux layer

Solder mask: The solder mask refers to the part of the board that needs to be coated with green oil; because it is a negative output, the actual effect of the part with the solder mask is not coated with green oil, but tinned, making it silvery white!

Soldering layer: Paste mask is used during machine placement. It corresponds to the pads of all patch components. It is the same size as the toplayer/bottomlayer layer and is used to open the steel mesh to leak tin.

Key points:Both layers are used for tin soldering, which does not mean that one is tinned and the other is coated with green oil. So, is there a layer that refers to the layer that is coated with green oil? As long as there is this layer on a certain area, it means that this area is What about the one with green oil insulation?

There is a solder layer for now, so the soldering pad on the finished PCB is covered with silver-white solder and not green oil. This is not surprising. However, the wiring part on the PCB we drew only has the toplayer or bottomlayer layer. , there is no solder layer, but the traces on the finished PCB board are coated with a layer of green oil. I have never seen such a layer before! We draw the PCB board, and the pads on it are by default

That can be understood like this:
1. The solder mask layer means opening a window on the entire solder mask green oil, with the purpose of allowing welding!
2. By default, areas without solder mask must be painted with green oil!
3. The paste mask layer is used for patch packaging! SMT packaging uses: toplayer layer, topsolder layer, toppaste layer, and toplayer and toppaste are the same size, topsolder is larger than them. DIP packaging only uses: topsolder and multilayer layers (after some decomposition, I found that the multilayer layer is actually the toplayer, bottomlayer, topsolder, bottomsolder layer size overlap), and topsolder/bottomlayer is larger than toplayer/bottomlayer.

Question: Is it correct to say that “the copper layer corresponding to the solder layer will be tinned or gold-plated only if there is copper?”

This sentence was said by a person who works in a PCB factory. What he means is: if you want the part painted on the solder layer to produce a tin-plated effect, then the corresponding solder layer part must have copper skin (i.e. : The area corresponding to the solder layer must have a toplayer or bottomlayer layer)!

Now we come to a conclusion: “The copper layer corresponding to the solder layer will be tinned or gold-plated only if it has copper.” This sentence is correct! The solder layer represents the area not covered by green oil!

The mechanical layer defines the appearance of the entire PCB board. In fact, when we talk about the mechanical layer, it refers to the appearance structure of the entire PCB board.

The prohibited wiring layer defines the boundary when we lay out copper with electrical characteristics. That is to say, after we first define the prohibited wiring layer, in the subsequent laying process, the lines with electrical characteristics that we lay cannot exceed the prohibited wiring. layer boundaries.

Topoverlay and bottomoverlay are the silk screen characters that define the top and bottom layers, which are generally the component numbers and some characters we see on the PCB board.

Toppaste and bottompaste are the top and bottom pad layers, which refer to the exposed copper and platinum that we can see. (For example, if we draw a wire on the top wiring layer, what we see on the PCB is just It is just a line, and it is covered by the entire green oil. However, if we draw a square or a point on the toppaste layer at the position of this line, the square and point on the printed board will not have green. It’s oil, but copper and platinum.

The top solder and bottom solder layers are just opposite to the previous two layers. It can be said that these two layers are covered with green layers. The multilayer layer is actually almost the same as the mechanical layer. As the name implies, this layer is Refers to all layers of the PCB board.


The top solder and bottom solder layers are just opposite to the previous two layers. It can be said that these two layers are the layers to be covered with green oil; because it is a negative output, the actual effect of the part with the solder mask is not actually Instead of green oil, it is tin-plated, making it silvery white!

So what are the main layers?

1. Signal layer

The signal layer is mainly used to lay out the wires on the circuit board.

Protel 99 SE provides 32 signal layers, including Top layer, Bottom layer and 30 MidLayer.

2. Internal plane layer (internal power/ground layer)

Protel 99 SE provides 16 internal power/ground planes.

This type of layer is only used for multi-layer boards and is mainly used to lay out power lines and ground lines. We call it double-layer board, four-layer board, and six-layer board, which generally refers to the number of signal layers and internal power/ground layers.

3. Mechanical layer

Protel 99 SE provides 16 mechanical layers, which are generally used to set the overall dimensions of the circuit board, data marks, alignment marks, assembly instructions and other mechanical information.

This information varies depending on the requirements of the design house or PCB manufacturer.

Execute the menu command Design|MechanicalLayer to set more mechanical layers for the circuit board. In addition, mechanical layers can be attached to other layers and output and displayed together.

4. Solder mask layer

Apply a layer of paint, such as solder mask, to all parts other than the solder pads to prevent tin from being applied to these parts.

The solder mask is used to match the pads during the design process and is generated automatically.

Protel 99 SE provides two solder resist layers: Top Solder (top layer) and Bottom Solder (bottom layer).

5. Paste mask layer

(solder paste protective layer, SMD patch layer) has a similar function to the solder mask layer. The difference is that it corresponds to the pad of the surface-mounted component during machine welding. Protel99 SE provides two solder paste protective layers: Top Paste (top layer) and Bottom Paste (bottom paste).

Mainly for SMD components on PCB boards. If all Dip (through-hole) components are placed on the board, there is no need to output the Gerber file on this layer. Before placing SMD components on the PCB, solder paste must be applied to each SMD pad. The stencil used for tin coating must require this Paste Mask file before the film can be processed.

The important point of the Gerber output of the Paste Mask layer should be clear, that is, this layer is mainly aimed at SMD components. At the same time, compare this layer with the Solder Mask introduced above to clarify the different functions of the two, because this layer can be seen from the film picture. The two film images are very similar.

6. Keep out layer (disable wiring layer)

Used to define the area on the circuit board where components and routing can be effectively placed.

Draw a closed area on this layer as the effective routing area. Automatic layout and routing cannot be performed outside this area.

7. Silkscreen layer

The silk screen layer is mainly used to place printed information, such as component outlines and annotations, various annotation characters, etc.

Protel 99 SE provides two screen printing layers: Top Overlay and Bottom Overlay. Generally, various annotation characters are on the top silk screen layer, and the bottom silk screen layer can be closed.

8. Multi layer

The pads and through-holes on the circuit board need to penetrate the entire circuit board and establish electrical connections with different conductive pattern layers. Therefore, the system specially sets up an abstract layer – multi-layer.

Generally, the pads and vias are arranged on multiple layers. If this layer is closed, the pads and vias cannot be displayed.

9. Drill layer

The drilling layer provides drilling information during the circuit board manufacturing process (such as pads and vias need to be drilled).

Protel 99 SE provides two drilling layers: Drillgride (drilling instruction map) and Drill drawing (drilling map).

To sum up, PCB soldering layer is an integral part of PCB manufacturing. It provides protection, isolation, wetting and heat transfer functions to help improve welding quality and efficiency. The correct selection and use of solder flux layer is very important to ensure the reliability and stability of PCB. With the continuous development of electronic technology, the application of PCB soldering flux layer will become more and more extensive and play a more important role in the performance and reliability of electronic equipment.


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