In PCB manufacturing, is wire patching permissible? What guidelines should be followed? For instance, what are the maximum dimensions for unfilled areas? How many repairs can be made on a single board? What characteristics may be impacted by a repaired circuit board?
“Fixing” is a conventional method for repairing circuit boards, primarily used for inner layers. It is relatively uncommon for manufacturers to permit repairs on outer layers. In cases where the operational frequency of electronic products is low, repairs can still salvage boards with open circuit issues. Typically, manufacturers establish the acceptable dimensions for repairs during production, with a common allowance of one repaired line per board.
However, most contemporary products operate at high frequencies, with many reaching transmission speeds of 1GHz or more (High Speed). Any defects in signal lines—such as nicks, protrusions, pinholes, or depressions—can lead to degradation of “Signal Integrity,” resulting in slower transmission speeds and unstable characteristic impedance. This is particularly critical for high-frequency microwave communication products, which have stringent requirements regarding line thickness and residual foot length. Consequently, these products cannot accommodate line repairs at all.
For products still eligible for repairs, the industry can refer to IPC-R-700 or the newer IPC-7721 guidelines. However, the methods and acceptance criteria for repairs are not formally documented in IPC standards, requiring coordination between both parties on specifications and quality.
Regarding PCB edge thickness, the board should not have edges when its thickness is measured in millimeters.
At what stage in the PCB process is edging generally required—during pressing or drilling? What board thickness prohibits grinding? Are there specific guidelines? Which equipment vendors supply edging machinery?
1. The primary purpose of edging is to mitigate issues caused by swarf during the cutting process. Therefore, this process can be applied to any stage that produces lint along the edges of the circuit board. It might be more accurate to refer to edging as trimming, as most manufacturers currently utilize trimming tools rather than grinding techniques.
2. Trimming procedures are carried out at various stages in the circuit board manufacturing process, including: post-material distribution, post-pressing, post-electroplating, post-finished product cutting, and gold finger trimming, among others. The primary objectives of these trimming actions focus on two main areas. First, they help prevent scratches to operators, machinery, and tools, ensuring the final product is aesthetically pleasing and easy to assemble. Second, they address potential contamination from burrs, which can easily detach and produce debris that is difficult to clean. If such debris contaminates production tanks, it can lead to issues like surface roughness and pollution. Naturally, for products with stringent quality standards, these treatments may sometimes be overlooked.
3. The significance of edging is particularly pronounced in exposure, electroplating, and other processes that are highly sensitive to particles. Skipping this step and proceeding directly can easily lead to quality issues. Regarding the use of trimming, quality considerations aside, the capabilities of the cutting process also play a crucial role. Without appropriate mechanisms for handling thinner circuit boards, many manufacturers tend to forgo trimming due to inadequate equipment. However, because thinner boards generally have less pronounced burrs, the impact is somewhat limited. Most manufacturers strive to enhance the cutting of thin boards and minimize burr formation to eliminate the need for edge grinding.
4. At what thickness does a circuit board become exempt from edging? There is no definitive answer, but it is commonly noted that for boards thinner than 16 mil, edging becomes increasingly challenging. Currently, there are machines available that can perform circuit board trimming, equipped with corner rounding functions. The design of this equipment aligns with the traditional concept of edge planing using V-shaped cutters; however, these V-shaped cutters are engineered as high-speed rotating tools that remove edge swarf as the circuit board moves through the process.
5. For thinner materials, this type of equipment must trim a small amount of material width to function effectively, which can be unsatisfactory for PCB manufacturers focused on material utilization. Nevertheless, practical experience suggests that the processed materials do contribute positively to quality improvement. The above observations are intended for reference only.
“Fixing” is a conventional method for repairing circuit boards, primarily used for inner layers. It is relatively uncommon for manufacturers to permit repairs on outer layers. In cases where the operational frequency of electronic products is low, repairs can still salvage boards with open circuit issues. Typically, manufacturers establish the acceptable dimensions for repairs during production, with a common allowance of one repaired line per board.
However, most contemporary products operate at high frequencies, with many reaching transmission speeds of 1GHz or more (High Speed). Any defects in signal lines—such as nicks, protrusions, pinholes, or depressions—can lead to degradation of “Signal Integrity,” resulting in slower transmission speeds and unstable characteristic impedance. This is particularly critical for high-frequency microwave communication products, which have stringent requirements regarding line thickness and residual foot length. Consequently, these products cannot accommodate line repairs at all.
For products still eligible for repairs, the industry can refer to IPC-R-700 or the newer IPC-7721 guidelines. However, the methods and acceptance criteria for repairs are not formally documented in IPC standards, requiring coordination between both parties on specifications and quality.
Regarding PCB edge thickness, the board should not have edges when its thickness is measured in millimeters.
At what stage in the PCB process is edging generally required—during pressing or drilling? What board thickness prohibits grinding? Are there specific guidelines? Which equipment vendors supply edging machinery?
1. The primary purpose of edging is to mitigate issues caused by swarf during the cutting process. Therefore, this process can be applied to any stage that produces lint along the edges of the circuit board. It might be more accurate to refer to edging as trimming, as most manufacturers currently utilize trimming tools rather than grinding techniques.
2. Trimming procedures are carried out at various stages in the circuit board manufacturing process, including: post-material distribution, post-pressing, post-electroplating, post-finished product cutting, and gold finger trimming, among others. The primary objectives of these trimming actions focus on two main areas. First, they help prevent scratches to operators, machinery, and tools, ensuring the final product is aesthetically pleasing and easy to assemble. Second, they address potential contamination from burrs, which can easily detach and produce debris that is difficult to clean. If such debris contaminates production tanks, it can lead to issues like surface roughness and pollution. Naturally, for products with stringent quality standards, these treatments may sometimes be overlooked.
3. The significance of edging is particularly pronounced in exposure, electroplating, and other processes that are highly sensitive to particles. Skipping this step and proceeding directly can easily lead to quality issues. Regarding the use of trimming, quality considerations aside, the capabilities of the cutting process also play a crucial role. Without appropriate mechanisms for handling thinner circuit boards, many manufacturers tend to forgo trimming due to inadequate equipment. However, because thinner boards generally have less pronounced burrs, the impact is somewhat limited. Most manufacturers strive to enhance the cutting of thin boards and minimize burr formation to eliminate the need for edge grinding.
4. At what thickness does a circuit board become exempt from edging? There is no definitive answer, but it is commonly noted that for boards thinner than 16 mil, edging becomes increasingly challenging. Currently, there are machines available that can perform circuit board trimming, equipped with corner rounding functions. The design of this equipment aligns with the traditional concept of edge planing using V-shaped cutters; however, these V-shaped cutters are engineered as high-speed rotating tools that remove edge swarf as the circuit board moves through the process.
5. For thinner materials, this type of equipment must trim a small amount of material width to function effectively, which can be unsatisfactory for PCB manufacturers focused on material utilization. Nevertheless, practical experience suggests that the processed materials do contribute positively to quality improvement. The above observations are intended for reference only.
