The bonding force between PCB coatings can be insufficient or too weak, making it challenging to withstand the coating stress, mechanical stress, and thermal stress generated during production and subsequent assembly processes. This can ultimately lead to varying degrees of separation between the coatings. Below are some factors that may contribute to poor board quality during production and processing:
1. Issues with substrate processing:
Particularly for thinner substrates (typically less than 0.8 mm), the substrate’s lack of rigidity makes it unsuitable for brushing machines. These machines may fail to effectively remove the protective layer designed to prevent oxidation of the copper foil during substrate production and processing. Although this layer is thin and easier to brush away, relying solely on chemical treatment may prove difficult. Therefore, it is crucial to monitor the processing conditions to avoid blistering on the board, which can arise from inadequate bonding between the copper foil and the chemical copper. This issue may also manifest as blackening and browning in the thin inner layers, leading to uneven coloration and localized black or brown spots.
2. Poor surface treatment phenomena:
Contamination from oils or other liquids mixed with dust during machining processes (such as drilling, lamination, and milling) can adversely affect surface treatment quality.
3. Poor copper sinking brush:
The pressure from the front grinding plate during copper sinking is excessive, leading to deformation of the holes. While the substrate remains intact, the overly heavy brushing can increase the roughness of the hole’s copper. This makes the copper foil in those areas prone to excessive roughening during the micro-etching process, which introduces potential quality risks. Therefore, it is crucial to enhance control over the brushing process, and optimal brushing parameters can be determined through wear scar tests and water film tests.
4. Washing issues:
Electroplating treatments for copper sinking involve extensive chemical processes, including various acids, alkalis, and non-polar organic solvents. If the board’s surface is not thoroughly cleaned, particularly from the copper sinking degreasing agent, it can lead to cross-contamination and inadequate local surface treatment, resulting in uneven defects and bonding issues. Thus, it’s essential to strengthen washing controls, focusing on washing water flow, quality, duration, and dripping time. In winter, lower temperatures significantly reduce washing effectiveness, necessitating closer attention to these controls.
5. Micro-etching in copper sinking pre-treatment and pattern electroplating:
Excessive micro-etching can cause substrate leakage at the orifices, leading to blistering around them. Conversely, insufficient micro-etching results in weak adhesion, also causing blistering. Therefore, stringent control over micro-etching is necessary. Typically, the corrosion depth for copper pre-treatment should be 1.5-2 microns, while for pattern plating, it should be 0.3-1 micron. If feasible, controlling micro-etching thickness or corrosion rate through chemical analysis and simple test weighing is ideal. A properly micro-etched board should exhibit a bright, uniform pink color without reflections. If the color is uneven or reflective, it indicates potential quality issues in pre-processing, warranting increased inspection. Additionally, factors such as copper content in the micro-etching tank, tank temperature, load capacity, and micro-etching agent concentration must be closely monitored.
6. Poor rework of heavy copper:
Reworked boards that undergo copper sinking or pattern transfer often suffer from inadequate plating during the rework process. Incorrect methods or improper control of micro-etching time can lead to surface bubbling. If poor copper sinking is identified on a rework line, the board can be degreased post-washing, followed by pickling and reworking without additional commissioning. Ideally, re-degreasing or micro-etching should be avoided. For boards that have already been thickened, the micro-etching tank should be adjusted for deplating, with careful time management. Testing one or two boards can help gauge deplating time to ensure effective results. After deplating, a soft brushing machine should be applied lightly, followed by copper sinking according to standard production processes, with slight adjustments to corrosion time as needed.
7. Oxidation of the board surface during production:
If immersion copper plates oxidize in the air, this can lead to lack of copper in the holes and rough surfaces, as well as surface bubbling. Prolonged storage in acidic solutions can also cause oxidation, creating a tough-to-remove oxide layer. Thus, during production, heavy copper plates should be thickened promptly and not stored for extended periods, ideally completing the thickening process within 12 hours.
8. Excessive activity of the copper precipitation solution:
A newly opened copper sinking solution tank or a high concentration of its three components, especially copper, can lead to excessive activity in the bath. This results in rough electroless copper deposition, with hydrogen and cuprous oxide contaminating the copper layer, which adversely affects the coating’s physical properties and bonding. To mitigate this, methods such as reducing copper content (by adding pure water), increasing complexing agent and stabilizer levels, and lowering the bath temperature can be employed.
9. Inadequate washing post-development during graphic transfer:
Insufficient washing after development, prolonged storage time, or excessive dust in the workshop can compromise the cleanliness of the board surface, potentially leading to subpar fiber processing outcomes and latent quality issues.
10. Organic contamination, particularly oil contamination, is more likely to occur in electroplating tanks for automated lines.
11. Timely replacement of the acid bath prior to copper plating is essential. Excessive contamination or high copper levels in the bath can affect board cleanliness and result in surface roughness.
12. In some factories during winter, it is crucial to ensure proper heating of the bath liquid. Special attention should be given to the electrification of the plates during production, especially in plating tanks with air agitation, such as copper-nickel baths. It’s advisable to add a warm water washing tank (at about 30-40 degrees) before nickel plating to ensure a dense and well-adhering initial nickel layer.
General sequence of PCB maintenance:
(1) Carefully inspect the faulty circuit board for visible signs of failure, such as burnt or cracked integrated circuits or other components, and look for any signs of disconnection or cracking.
(2) Understand the failure process, analyze its cause, and infer the likely locations of faulty devices.
(3) Analyze the application nature of the faulty circuit board and catalog the types of integrated circuits used.
(4) Organize the integrated circuits based on their location and likelihood of failure.
(5) Employ various detection methods in order of probability to gradually narrow down the failure scope.
(6) Identify the specific faulty device. When replacing an integrated circuit, it is best to use an IC socket for trial replacements.
(7) If issues persist after testing, continue testing until all faults on the circuit board are resolved.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
1. Issues with substrate processing:
Particularly for thinner substrates (typically less than 0.8 mm), the substrate’s lack of rigidity makes it unsuitable for brushing machines. These machines may fail to effectively remove the protective layer designed to prevent oxidation of the copper foil during substrate production and processing. Although this layer is thin and easier to brush away, relying solely on chemical treatment may prove difficult. Therefore, it is crucial to monitor the processing conditions to avoid blistering on the board, which can arise from inadequate bonding between the copper foil and the chemical copper. This issue may also manifest as blackening and browning in the thin inner layers, leading to uneven coloration and localized black or brown spots.
2. Poor surface treatment phenomena:
Contamination from oils or other liquids mixed with dust during machining processes (such as drilling, lamination, and milling) can adversely affect surface treatment quality.
3. Poor copper sinking brush:
The pressure from the front grinding plate during copper sinking is excessive, leading to deformation of the holes. While the substrate remains intact, the overly heavy brushing can increase the roughness of the hole’s copper. This makes the copper foil in those areas prone to excessive roughening during the micro-etching process, which introduces potential quality risks. Therefore, it is crucial to enhance control over the brushing process, and optimal brushing parameters can be determined through wear scar tests and water film tests.
4. Washing issues:
Electroplating treatments for copper sinking involve extensive chemical processes, including various acids, alkalis, and non-polar organic solvents. If the board’s surface is not thoroughly cleaned, particularly from the copper sinking degreasing agent, it can lead to cross-contamination and inadequate local surface treatment, resulting in uneven defects and bonding issues. Thus, it’s essential to strengthen washing controls, focusing on washing water flow, quality, duration, and dripping time. In winter, lower temperatures significantly reduce washing effectiveness, necessitating closer attention to these controls.
5. Micro-etching in copper sinking pre-treatment and pattern electroplating:
Excessive micro-etching can cause substrate leakage at the orifices, leading to blistering around them. Conversely, insufficient micro-etching results in weak adhesion, also causing blistering. Therefore, stringent control over micro-etching is necessary. Typically, the corrosion depth for copper pre-treatment should be 1.5-2 microns, while for pattern plating, it should be 0.3-1 micron. If feasible, controlling micro-etching thickness or corrosion rate through chemical analysis and simple test weighing is ideal. A properly micro-etched board should exhibit a bright, uniform pink color without reflections. If the color is uneven or reflective, it indicates potential quality issues in pre-processing, warranting increased inspection. Additionally, factors such as copper content in the micro-etching tank, tank temperature, load capacity, and micro-etching agent concentration must be closely monitored.
6. Poor rework of heavy copper:
Reworked boards that undergo copper sinking or pattern transfer often suffer from inadequate plating during the rework process. Incorrect methods or improper control of micro-etching time can lead to surface bubbling. If poor copper sinking is identified on a rework line, the board can be degreased post-washing, followed by pickling and reworking without additional commissioning. Ideally, re-degreasing or micro-etching should be avoided. For boards that have already been thickened, the micro-etching tank should be adjusted for deplating, with careful time management. Testing one or two boards can help gauge deplating time to ensure effective results. After deplating, a soft brushing machine should be applied lightly, followed by copper sinking according to standard production processes, with slight adjustments to corrosion time as needed.
7. Oxidation of the board surface during production:
If immersion copper plates oxidize in the air, this can lead to lack of copper in the holes and rough surfaces, as well as surface bubbling. Prolonged storage in acidic solutions can also cause oxidation, creating a tough-to-remove oxide layer. Thus, during production, heavy copper plates should be thickened promptly and not stored for extended periods, ideally completing the thickening process within 12 hours.
8. Excessive activity of the copper precipitation solution:
A newly opened copper sinking solution tank or a high concentration of its three components, especially copper, can lead to excessive activity in the bath. This results in rough electroless copper deposition, with hydrogen and cuprous oxide contaminating the copper layer, which adversely affects the coating’s physical properties and bonding. To mitigate this, methods such as reducing copper content (by adding pure water), increasing complexing agent and stabilizer levels, and lowering the bath temperature can be employed.
9. Inadequate washing post-development during graphic transfer:
Insufficient washing after development, prolonged storage time, or excessive dust in the workshop can compromise the cleanliness of the board surface, potentially leading to subpar fiber processing outcomes and latent quality issues.
10. Organic contamination, particularly oil contamination, is more likely to occur in electroplating tanks for automated lines.
11. Timely replacement of the acid bath prior to copper plating is essential. Excessive contamination or high copper levels in the bath can affect board cleanliness and result in surface roughness.
12. In some factories during winter, it is crucial to ensure proper heating of the bath liquid. Special attention should be given to the electrification of the plates during production, especially in plating tanks with air agitation, such as copper-nickel baths. It’s advisable to add a warm water washing tank (at about 30-40 degrees) before nickel plating to ensure a dense and well-adhering initial nickel layer.
General sequence of PCB maintenance:
(1) Carefully inspect the faulty circuit board for visible signs of failure, such as burnt or cracked integrated circuits or other components, and look for any signs of disconnection or cracking.
(2) Understand the failure process, analyze its cause, and infer the likely locations of faulty devices.
(3) Analyze the application nature of the faulty circuit board and catalog the types of integrated circuits used.
(4) Organize the integrated circuits based on their location and likelihood of failure.
(5) Employ various detection methods in order of probability to gradually narrow down the failure scope.
(6) Identify the specific faulty device. When replacing an integrated circuit, it is best to use an IC socket for trial replacements.
(7) If issues persist after testing, continue testing until all faults on the circuit board are resolved.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
