1. [PCB parts falling] seems to be a common concern among many process and quality control engineers, yet the challenges faced vary widely. Many novices encounter such issues and often struggle with where to begin their analysis. Here, I will share my methods and steps for your consideration.
2. Typically, when components on a circuit board fall off, most issues are related to “soldering quality.” The final conclusions often point to one or a combination of the following causes:
1. Issues with the surface treatment of the circuit board.
2. Problems with the surface treatment of the component’s solder pads.
3. Inadequate storage conditions leading to oxidation of boards or parts.
4. Inconsistencies in the reflow temperature process.
5. Insufficient solder strength to withstand external forces in actual use.
3. Several steps are involved in analyzing the failure of circuit board components:
The following outlines the steps for analyzing falling components on a circuit board.
4. The first step is to gather information.
This is crucial; if the source of information is flawed, no amount of enthusiasm will yield meaningful results. First, confirm the description of the undesirable phenomenon with the respondent, and seek the following details:
1. What occurred? Please provide a clear description of the undesirable phenomenon. Under what conditions did the components fall? Has the product been dropped? What environment was it in (gas station, outdoor, indoor, air-conditioned)? Were any special tests performed (high or low temperature)?
2. Does the issue arise on the client side? Is it during the production process? At which step of the process was the issue identified?
3. When did the problem manifest? Was it discovered during production or during finished product testing? Are defective products concentrated within the same date code?
4. What is the board’s surface treatment? Is it ENIG, OSP, or HASL? ENIG can experience black nickel issues, HASL may encounter poor tin adhesion after the second side, and OSP can have tin adhesion problems after its expiration.
5. What is the board thickness? 0.8mm, 1.0mm, 1.2mm, or 1.6mm? Thinner boards are more prone to deformation and bending, increasing the risk of tin cracking.
6. What is the surface treatment of the component leads? Is it matte tin or gold-plated? What is the primary composition of the solder paste? Is it SAC305 (tin, silver, and copper) or SCN (tin, copper, nickel)? The melting points vary among different solder pastes.
7. Ideally, you should access the reflow measurement curve from that time. The second step involves acquiring defective products and retaining evidence for further analysis. Please obtain the actual PCB from the defective product. If the components have fully fallen off, it’s best to also gather the dropped components for a thorough analysis. The more defective products collected, the better.
The third step is to assess the solderability of the circuit board. Once you have the defective product, evaluate both the solderability of the circuit board and the component leads, noting any differences. When checking solderability, it’s advisable to use a microscope to identify subtle issues.
To analyze and troubleshoot the problem with the dropped components, check if solder is present on the circuit board’s pads for defects like solder rejection or de-wetting. Such issues often stem from inadequate surface treatment or poor storage conditions leading to pad oxidation. Sometimes, insufficient reflow furnace temperature can cause soldering failures; if a soldering iron fails to solder the pads, it indicates a potential issue with the PCB itself.
Please note: Some tin-plated components utilize “tin, copper, nickel (SCN)” composition, which has a melting point 10°C higher than SAC305. SAC305 melts at 217°C; SCN at 227°C. If oxidation from poor storage conditions is suspected, you may ask the PCB supplier to inspect the product or return the PCB for analysis. In case of disputes, measure the thickness of the surface treatment first. Typically, ENIG requires checking gold and nickel layer thicknesses, while HASL necessitates measuring the tin layer, and OSP should be inspected for oxidation.
If disputes persist, slicing may be necessary for a detailed analysis. The fourth step is to evaluate the solderability of the dropped components. Observing the solderability under a microscope is recommended to identify subtle phenomena that are not visible to the naked eye.
To determine the quality of tin on the component leads, check the composition of the plating layer against the reflow furnace temperature. For components utilizing silver plating, be aware that the silver is often just a surface layer, making it susceptible to SAC solder paste, which can reduce soldering strength.
Note that some components may expose copper at their cut surface, which is typically not plated. This area generally does not require tin but is designed to be in non-critical locations.
The fifth step involves checking if the solder pads have detached along with the dropped component leads. If there are no solderability issues with the PCB or component leads, inspect whether the pads on the PCB are also detached. If they are, it confirms that the soldering between the component and PCB was good, indicating no reflow issues.
If the pads remain intact, verify whether the reflow temperature curve met solder paste requirements. If excess defective products exist, test whether the dropped components can be soldered back to the PCB. Successful re-soldering indicates that adjustments to temperature or solder paste may resolve the problem. A thrust test should compare boards confirmed as problem-free against those with adjusted solder paste and temperature curves. Any differences may warrant checking the PCB’s surface treatment, as poor surface conditions can lead to local pad oxidation.
The sixth step involves examining the area where the part fell. Observe the peeling surface of the PCB and component leads under a microscope to determine if the section appears rough or smooth. A rough surface typically indicates a sudden external force caused the components to detach, while a smooth surface suggests failure due to prolonged vibration. In the case of an ENIG PCB, look for potential black nickel issues that could lead to peeling at the nickel layer.
The seventh step is to conduct a biopsy to check IMC and perform EDX analysis. If previous steps fail to identify the cause of the falling components, destructive slicing may be required. Both the PCB and the dropped components should be analyzed during this process.
The purpose of slicing serves two objectives:
1. To check for IMC generation, its uniformity, and use EDX to identify IMC composition. Uneven or local IMC growth can reduce solder strength and impact component stability, often due to oxidation or inadequate temperature.
Extended reading: The correlation between PCB soldering strength and IMC.
2. To confirm where the fracture occurred. If the fracture point is within the IMC layer, it typically indicates solderability is not the issue, but the solder strength was insufficient to withstand external forces. This may necessitate enhancements like Underfill or dispensing for BGA or critical components.
Conversely, if the fracture surface is at the PCB end, the problem may lie within the PCB. If the fracture is at the component’s end, it leans more towards a component-related issue.
2. Typically, when components on a circuit board fall off, most issues are related to “soldering quality.” The final conclusions often point to one or a combination of the following causes:
1. Issues with the surface treatment of the circuit board.
2. Problems with the surface treatment of the component’s solder pads.
3. Inadequate storage conditions leading to oxidation of boards or parts.
4. Inconsistencies in the reflow temperature process.
5. Insufficient solder strength to withstand external forces in actual use.
3. Several steps are involved in analyzing the failure of circuit board components:
The following outlines the steps for analyzing falling components on a circuit board.
4. The first step is to gather information.
This is crucial; if the source of information is flawed, no amount of enthusiasm will yield meaningful results. First, confirm the description of the undesirable phenomenon with the respondent, and seek the following details:
1. What occurred? Please provide a clear description of the undesirable phenomenon. Under what conditions did the components fall? Has the product been dropped? What environment was it in (gas station, outdoor, indoor, air-conditioned)? Were any special tests performed (high or low temperature)?
2. Does the issue arise on the client side? Is it during the production process? At which step of the process was the issue identified?
3. When did the problem manifest? Was it discovered during production or during finished product testing? Are defective products concentrated within the same date code?
4. What is the board’s surface treatment? Is it ENIG, OSP, or HASL? ENIG can experience black nickel issues, HASL may encounter poor tin adhesion after the second side, and OSP can have tin adhesion problems after its expiration.
5. What is the board thickness? 0.8mm, 1.0mm, 1.2mm, or 1.6mm? Thinner boards are more prone to deformation and bending, increasing the risk of tin cracking.
6. What is the surface treatment of the component leads? Is it matte tin or gold-plated? What is the primary composition of the solder paste? Is it SAC305 (tin, silver, and copper) or SCN (tin, copper, nickel)? The melting points vary among different solder pastes.
7. Ideally, you should access the reflow measurement curve from that time. The second step involves acquiring defective products and retaining evidence for further analysis. Please obtain the actual PCB from the defective product. If the components have fully fallen off, it’s best to also gather the dropped components for a thorough analysis. The more defective products collected, the better.
The third step is to assess the solderability of the circuit board. Once you have the defective product, evaluate both the solderability of the circuit board and the component leads, noting any differences. When checking solderability, it’s advisable to use a microscope to identify subtle issues.
To analyze and troubleshoot the problem with the dropped components, check if solder is present on the circuit board’s pads for defects like solder rejection or de-wetting. Such issues often stem from inadequate surface treatment or poor storage conditions leading to pad oxidation. Sometimes, insufficient reflow furnace temperature can cause soldering failures; if a soldering iron fails to solder the pads, it indicates a potential issue with the PCB itself.
Please note: Some tin-plated components utilize “tin, copper, nickel (SCN)” composition, which has a melting point 10°C higher than SAC305. SAC305 melts at 217°C; SCN at 227°C. If oxidation from poor storage conditions is suspected, you may ask the PCB supplier to inspect the product or return the PCB for analysis. In case of disputes, measure the thickness of the surface treatment first. Typically, ENIG requires checking gold and nickel layer thicknesses, while HASL necessitates measuring the tin layer, and OSP should be inspected for oxidation.
If disputes persist, slicing may be necessary for a detailed analysis. The fourth step is to evaluate the solderability of the dropped components. Observing the solderability under a microscope is recommended to identify subtle phenomena that are not visible to the naked eye.
To determine the quality of tin on the component leads, check the composition of the plating layer against the reflow furnace temperature. For components utilizing silver plating, be aware that the silver is often just a surface layer, making it susceptible to SAC solder paste, which can reduce soldering strength.
Note that some components may expose copper at their cut surface, which is typically not plated. This area generally does not require tin but is designed to be in non-critical locations.
The fifth step involves checking if the solder pads have detached along with the dropped component leads. If there are no solderability issues with the PCB or component leads, inspect whether the pads on the PCB are also detached. If they are, it confirms that the soldering between the component and PCB was good, indicating no reflow issues.
If the pads remain intact, verify whether the reflow temperature curve met solder paste requirements. If excess defective products exist, test whether the dropped components can be soldered back to the PCB. Successful re-soldering indicates that adjustments to temperature or solder paste may resolve the problem. A thrust test should compare boards confirmed as problem-free against those with adjusted solder paste and temperature curves. Any differences may warrant checking the PCB’s surface treatment, as poor surface conditions can lead to local pad oxidation.
The sixth step involves examining the area where the part fell. Observe the peeling surface of the PCB and component leads under a microscope to determine if the section appears rough or smooth. A rough surface typically indicates a sudden external force caused the components to detach, while a smooth surface suggests failure due to prolonged vibration. In the case of an ENIG PCB, look for potential black nickel issues that could lead to peeling at the nickel layer.
The seventh step is to conduct a biopsy to check IMC and perform EDX analysis. If previous steps fail to identify the cause of the falling components, destructive slicing may be required. Both the PCB and the dropped components should be analyzed during this process.
The purpose of slicing serves two objectives:
1. To check for IMC generation, its uniformity, and use EDX to identify IMC composition. Uneven or local IMC growth can reduce solder strength and impact component stability, often due to oxidation or inadequate temperature.
Extended reading: The correlation between PCB soldering strength and IMC.
2. To confirm where the fracture occurred. If the fracture point is within the IMC layer, it typically indicates solderability is not the issue, but the solder strength was insufficient to withstand external forces. This may necessitate enhancements like Underfill or dispensing for BGA or critical components.
Conversely, if the fracture surface is at the PCB end, the problem may lie within the PCB. If the fracture is at the component’s end, it leans more towards a component-related issue.
