The production process of PCB is very complex, and its production process mainly includes PCB layout, core board production, inner PCB layout transfer, core board drilling and inspection, lamination, drilling, copper chemical precipitation of the hole wall, outer PCB layout transfer, outer PCB etching and other steps. Errors at every step can lead to many problems in the PCB manufacturing process as well as the assembly process. Therefore, in this article, in order to help complete the PCB manufacturing process smoothly, we have made 11 suggestions.
Consistent manufacturing documents and design files
In the production and manufacturing, PCB manufacturing documents and design file must be unified with the manufacturer. You also need to ensure that the process meets your needs, such as clearance, size, spacing, and other aspects such as physical design.
The manufacturer will check the manufacturing documentation, especially the copper and mask in each layer, to ensure that the board can be manufactured reliably.
Manufacturing instructions are also important because they provide all the other information used to manufacture a bare PCB. Such as conformal coatings, surface finish, specific materials to be used (LPI solder mask, etc.), impedance requirements, layup/material specifications, etc. are specified in the PCB fabrication drawing. Complete and clear manufacturing instructions help ensure that the design can be produced smoothly.
Bill of materials management
The purchase of materials, query of components, whether they are in stock, delivery, whether to stop production, etc., can be completed through BOM file parsing.
In addition, in the PCB design process, you should select more common components as far as possible, and should have alternative components, so as to reduce the risk to a relatively low level. One advantage of using common components is that they are easier to buy and more abundant.
Reduce through-hole components
SMT components are easy to place by placement machines, but many large capacitors on PCBs need to be manually placed and soldered. Through-hole components are generally more expensive than SMDs,and they require manual soldering, and take more time.
Connectors are the most common THT components and are prone to manufacturing problems. If the connector is repeatedly inserted into the component with which it mates, it is prone to problems. Therefore, try to minimize the use of THT components and use SMT components as much as possible.
Provide heat dissipation
The heat generated during the operation of electronic equipment makes the internal temperature of the equipment rise rapidly, if the heat is not dissipated in time, the equipment will continue to heat up, the device will fail due to overheating, and the reliability of the electronic equipment will decrease. Therefore, it is important to dissipate heat from the board.
Most of the copper on the PCB absorbs heat during soldering and can lead to cold solder joints, which are to be avoided. Ensure adequate heat dissipation for THT connections connected to large areas of copper, such as ground planes or power planes.
Install the PCB correctly
Use keyed connectors so that connectors can only be inserted one way. Note how to insert the PCB upside down using the following connectors.
If the connector is a ribbon cable, it is especially possible to stagger the mounting holes, allowing the board to be mounted in only one position. Make sure that the screen print identifies the orientation of the diode and secures one pin to the IC. Many assembly problems are caused by missing or incorrect orientation markings.
Leave enough space
Enough space needs to be left for the PCB board, and if the components on the PCB are too crowded, it will lead to short circuits and other incorrect assembly, which will increase costs.
Keep traces within the edge of the PCB and also keep the components away from the edge of the board. During depanel , components close to the board may crack or be damaged.
Another good tip is to place and route the bypass cap immediately after placing the required components. Be sure to place the bypass capacitor close to its IC and power the IC after the capacitor.
Silk screen
Keep silkscreen graphics away from pads and follow the manufacturer’s minimum font size and lineweight guidelines.
PCB silkscreen rules
1. There should be complete relevant information and anti-static identification of the manufacturer on the PCB.
2. Silk screen characters follow the principle of left-to-right, bottom-up, and the direction is the same.
3. The polarity of the polar element is indicated on the silk screen, and the polarity direction mark will be easy to identify.
4. All components, mounting holes and positioning holes have corresponding silk screen labels.
5. The direction of the connector is indicated on the silkscreen.
6. The silkscreen printing position of the finished board information such as PCB board name, date, version number should be clear.
7. The identifier of the device on the PCB must be the same as the identifier in the BOM.
Prevent PCB tombstone or monument
The monument is lifted by one of the SMD’s pads during reflow soldering.
This is caused by uneven pad heating due to traces not leaving the pad evenly. You can prevent misalignment and tombstone phenomena by ensuring that the pads are heated evenly.
The capabilities of PCB manufacturers
This is an important part, if your manufacturer does not have this process capability, there is no need to choose him. In addition, it is necessary to communicate and ask, such as whether small holes and traces are needed. A good understanding of your manufacturer can help you reduce costs.
Setting components aside as much as possible while meeting the needs requires additional assembly steps and increases the chance of assembly errors.
DFM analysis
PCB manufacturing problems are: acid traps, copper chips, silkscreen distance direction, etc., so DFM analysis before production is very important, a good DFM tool can avoid these problems before PCB manufacturing.
Too close a spacing between components and pads can cause problems during soldering. During wave soldering, devices and large components can obscure smaller components, resulting in poor solder joints for smaller components. At the same time, PCB rework and testing can also greatly increase the difficulty.
PCB shell
Ensuring that the PCB has a suitable shell can avoid PCB damage.
The circuit board may need to be protected from factors such as temperature, airborne particles, and ultraviolet rays. Depending on the usage environment, the shell will provide some different functions. It is important to choose the right PCB shell material, such as plastic housing, which is highly malleable and can survive in humid environments with low cost. In addition, the easy-to-modify housing can reduce the overall PCB assembly cost.
