Why does the PCB open up? How to improve?
PCB circuit open and short circuit is a problem that PCB manufacturers encounter on an almost daily basis, and has always plagued production and quality management personnel. It is caused by the lack of shipments and the lack of shipments, delivery delays, and customer complaints are among industry comparisons. Difficult to solve the problem. I have more than 20 years of working experience in the PCB manufacturing industry. I mainly work in production management, quality management, process management and cost control. We have accumulated some experience in the improvement of PCB opening and short circuit problems. Now we have formed a text for the purpose of summing it up for discussion among our peers and we look forward to the management and production and quality of our colleagues as a reference.
We first categorize the main causes of PCB open circuit as follows:
The reasons for the above analysis and improvement methods are listed as follows:
First, open circuit caused by exposed substrate:
1. The copper-clad laminate is scratched before entering the warehouse; 2. The copper-clad laminate is scratched during the material-opening process; 3. The copper-clad laminate is scratched by the drill nozzle during drilling; 4. The laminate is drawn during the transfer process. 5. Injury; 5. Copper foil was scratched due to improper operation when stacking plates after sinking copper; 6. The surface copper foil was scratched when the production plate was over horizontal.
Improve methods:
1. The IQC of the CCL must be sampled before entering the warehouse to check whether there is any scratched substrate on the board surface. If there is any problem, please contact the supplier in time and make appropriate treatment according to the actual situation.
2. The copper-clad laminate is scratched during the process of blanking. The main reason is that there are hard objects on the surface of the material feeder. When the materials are opened, the copper-clad laminates and the sharps will cause the copper foil to scratch and form the exposed substrate. Before the material, the countertop must be carefully cleaned to ensure that the countertop is smooth and free of hard objects.
3, CCL was scratched by drilling nozzle during drilling. The main reason is that the spindle clamp nozzle is worn, or there is debris in the clamp nozzle is not clean, when the drilling nozzle is caught, the drill nozzle is not on the top. The length of the drilling nozzle is slightly longer, and the raised height of the drilling hole is not enough. When the machine tool moves, the tip of the drill scratches the copper foil to form the exposed substrate.
a. It can be changed by the number of times the knife is recorded or according to the degree of wear of the clamp.
b. Periodically clean the clamps according to the operating procedures to ensure that there are no debris in the clamps.
4, the sheet was scratched during the transfer process:
a. The amount of plates lifted by the handling personnel at one time is too much and the weight is too large. The plates are not lifted when they are transported, but instead they are dragged up, resulting in friction between the plate corners and the plate surface and scratching the plate surface; b. Because they did not put neatly, in order to reorganize and force to push the board, causing friction between the board and the board scratches the board.
5, after sinking copper, plated plate after the entire plate was improperly handled by the scratch:
When the plate is stored after electroplating after plating, the plates are stacked together. When the plate is stacked, the weight is not small. When the plate is lowered, the plate angle is downward and a gravitational acceleration is added to form a strong impact force. Impact on the board surface, resulting in scratches on the board surface exposed substrate.
6, the production board was scratched when crossing the level machine:
a. The baffle of the plate mill may sometimes come into contact with the surface of the plate. The edges of the baffle are generally not even and the objects are convex. When the plate is over, the surface of the plate is scratched.
b. Stainless steel drive shaft, due to damage to sharp objects, scratches the copper surface and exposes the substrate when the board is over.
In summary, for the scratched exposed substrate phenomenon after sinking copper, if the line is displayed in the form of an open circuit or line gap, it is easy to judge; if it is scratched exposed substrate before the sinking copper, When it is on the road, after sinking copper, it sinks to a layer of copper. The thickness of the copper foil on the line is obviously reduced. It is difficult to detect when the back is open or short-circuit test. This may cause customers to use excessively large The current caused by the line is blown, the potential quality problems and the resulting economic losses are considerable.
Second, no hole open:
1. Immersion copper without pores; 2. No pores caused by oil in the pores; 3. No pores caused by excessive micro-etching; 4. No pores caused by poor plating; 5. No holes caused by drilling holes or dust plug holes Holes.
Improvements:
1, sink copper without hole:
a. Non-porosity caused by the pore modifying agent: This is because the chemical concentration of the pore modifying agent is unbalanced or fails. The function of the sizing agent is to adjust the electrical properties of the insulating substrate on the hole wall so as to facilitate the subsequent adsorption of palladium ions and ensure that the chemical copper is completely covered. If the chemical concentration of the sizing agent is unbalanced or fails, voiding may result.
b. Activator: Its main components are pd, organic acids, stannous ions and chlorides. The pore wall must have a uniform deposition of metal palladium, we must control all aspects of the parameters to meet the requirements, with our current activator as an example:
1. The temperature is controlled at 35-44°C. If the temperature is low, the density of palladium deposits is not enough, and the chemical copper coverage is not complete; the temperature is high because the reaction is too fast and the material cost increases.
2. Concentration colorimetry is controlled at 80% to 100%. If the concentration is too low, the density of palladium deposition is not enough, and the chemical copper coverage is incomplete; the concentration is high because the reaction is too fast and the material cost is increased.
3, in the production process to maintain a good solution of the activator, if the degree of pollution is more serious, will cause the deposition of the pore wall of the palladium is not dense, follow-up chemical copper coverage is not complete.
c. Accelerator: The main ingredient is organic acid, which is used to remove stannous and chloride ion compounds adsorbed on the pore walls, exposing the catalytic metal palladium after the subsequent reaction. The accelerator we use now has a chemical concentration of 0.35 to 0.50 N. If the concentration is high, the metal palladium is removed, resulting in incomplete chemical copper coverage. If the concentration is low, the removal of stannous and chloride ion compounds adsorbed on the pore walls is not effective, resulting in incomplete chemical copper coverage.
d. The control of chemical copper parameters is the key to good or bad coverage of chemical copper. Take the syrup parameters currently used by our company as an example:
1, the temperature is controlled at 25 ~ 32 °C, the temperature is low, the liquid activity is not good, resulting in no pores; if the temperature exceeds 38 °C, because the liquid reaction is fast, the release of copper ions is also fast, easy to cause the copper on the surface and Rework or even scrapped, when the sinking copper liquid immediately filtered, or liquid may cause scrap.
2, Cu 2+ control in 1.5 ~ 3.0g / L, Cu 2+ content is low, the liquid activity is not good, will cause poor pores; if the concentration exceeds 3.5g / L, because the liquid reaction is fast, the release of copper ions is also fast, causing The copper on the board surface is reworked or even scrapped, so that the copper sink liquid must be filtered immediately, otherwise the liquid medicine may cause scrap. The Cu2+ control is mainly controlled by the addition of a copper-impregnated A solution.
3, NaOH control at 10.5 ~ 13.0g / L is appropriate, low NaOH content of the liquid activity is not good, will cause poor pores. The NaOH control is mainly controlled by the addition of the copper-impregnated liquid B. The liquid B contains the stabilizer of the liquid. Under normal conditions, the liquid A and the liquid B are supplemented by 1:1.
4, HCHO control in the 4.0 ~ 8.0g / L, HCHO content is low, the liquid activity is not good, resulting in poor pores, if the concentration exceeds 8.0g / L, due to rapid liquid reaction, the release of copper ions is also fast, causing The copper on the board surface is reworked or even scrapped, so that the copper sink liquid must be filtered immediately, otherwise the liquid medicine may cause scrap. The HCHO control is mainly controlled by the addition of the copper-impregnated liquid C. The liquid A also contains the chemical components of the HCHO. Therefore, when the HCHO is added, the HCHO concentration increase amount when the liquid A is added is first calculated.
5. The copper loading is controlled at 0.15 to 0.25 ft2/L. Poorly loaded fluids cause poor pore formation. If the loading exceeds 0.25 ft2/L, the copper ions release due to rapid liquid reaction. Also fast, causing the copper on the surface to be reworked or even scrapped, so that the copper-impregnated liquid should be filtered immediately, otherwise the liquid may cause scrap. During production, the first cylinder plate must be dragged with a copper plate to activate the activity of the copper-enriched liquid and facilitate the subsequent reaction of the copper-impregnated product to ensure the density of the chemical copper in the hole and increase the coverage.
Suggestion: In order to achieve the balance and stability of the above parameters, the copper cylinder should be filled with A and B fluids. An automatic feeder should be configured to better control the chemical components; at the same time, the automatic control device is used to make the copper sink temperature. The temperature of the line solution is under control.
2. There is no pore in the pores due to residual wet film oil:
a. When the silk screen printing wet film is printed, one plate is scraped once to ensure that there is no oil accumulation at the bottom of the screen. Under normal circumstances, there will be no phenomenon of residual wet film oil in the hole.
b. Screen printing wet film is used in the 68 ~ 77T screen, if the wrong screen, such as ≤ 51T, the hole may leak into the wet film oil, the development of the hole may not develop the oil clean, electroplating At this time, no pores will be formed because the metal layer cannot be plated. If the mesh is high, there is a possibility that the thickness of the ink is insufficient, and the plating film is broken by the current during plating, causing many metal dots between the circuits and even a short circuit.
3, roughening caused by non-porous:
a. If the chemical roughening plate surface is used before the line, the parameters such as temperature, concentration, and roughening time of the roughening solution should be controlled. Otherwise, the copper thickness of the plated hole may be too thin to withstand the dissolution of the roughening solution. Copper does not cause pores.
b. In order to strengthen the binding force of the plating layer and the base copper, the electroplating pretreatment must be chemically roughened before electroplating, so the parameters such as the temperature, concentration, and roughening time of the roughening solution should be controlled well, otherwise it may cause non-porous. Problems.
4, plating without hole:
a. When the diameter is relatively large (≥5:1) during electroplating, there will be air bubbles in the hole. This is because the vibration force is insufficient to escape the air in the hole and the ion exchange cannot be realized, so that the hole is not plated. On copper/tin, the copper in the hole is etched away during etching, resulting in no hole.
b. Larger diameter (≥5:1). Before electroplating, the oxidation phenomenon in the pores is not removed. The plating phenomenon occurs during plating. There is no copper/tin plating or the copper/tin plating is very thin. Etching resistance does not result in etching of the copper in the hole, resulting in no hole.
5, drilling Tsui hole or dust plug hole without hole:
a. The service life of the drilling nozzle during drilling is not set well, or the drill nozzle used is worn more seriously, such as notches, not sharp, and the hole is burnt because the frictional force is too large and the heat is generated. No pores.
b. The suction of the vacuum cleaner is not large enough, or the project is not optimized. When the hole is drilled, there is dust blocking in the hole. When the chemical copper is not covered with copper, the hole is not formed.
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