How to deal with sensitive components in PCBA?

A sensitive component refers to a circuit component that is easily damaged by factors like overheating, static electricity, or improper handling. These components include integrated circuits, diodes, microprocessors, transistors, and capacitors. Properly handling these components is crucial during PCBA processing, as their delicate structures are susceptible to permanent damage or failure. Even a minor electrostatic discharge (ESD) or slight temperature increase can lead to significant damage or shorten their operational lifespan. For this reason, FS Technology implements necessary technologies and measures to ensure the quality of our PCB assembly services when dealing with sensitive components.

Best Practices for Handling Sensitive Electronic Components

Grounding and ESD protection

The fundamental technique for handling sensitive components in a PCBA project involves ensuring accurate grounding and employing ESD protection circuits. Specific measures include:

Grounding Your Workstation: Ensure that your workstation is properly grounded from the outset. This entails connecting it to a suitable ground source. This practice helps dissipate static charges that may accumulate on surfaces and bodies, thus preventing ESD issues during the PCB assembly process.
Implementing an ESD Mat: In addition to using an antistatic wrist strap, incorporating an antistatic mat in the workspace is advisable. These mats establish a conductive pathway for static charges, effectively channeling any potential ESD problems harmlessly to the ground. It’s important that the ESD mat covers the entire work area.
Using ESD-Safe Tools and Equipment: Utilizing instruments and tools that are ESD-safe is a critical aspect of achieving reliable ESD protection. These tools are crafted from materials that neither generate nor retain static charges. Examples of ESD-safe instruments include tweezers, pliers, and soldering irons.

How to Use Antistatic Wrist Straps

Simple and practical tool, one end is worn on the worker’s wrist, while the other end is connected to a grounding point. This tool effectively discharges static electricity generated by the human body:

Prepare: Prior to commencing any PCBA work, ensure that the working area is properly grounded. This involves establishing a reliable connection to ground using an ESD grounding plug or grounding wire.
Use a Wrist Strap: Wear the wrist strap securely around your wrist, ensuring that it fits snugly. The conductive plate within the strap should have direct contact with your skin.
Secure the Strap: On the opposite end of the wrist strap, you’ll find an alligator clip or banana plug. Attach this firmly to the grounding point on the working bench or the designated grounding surface.
Check for Continuity: Some antistatic wrist straps come equipped with built-in continuity testers. These testers indicate whether the strap is properly connected and functional. Verify the tester to confirm the strap’s operational status.
Keep the Strap On: Once the wrist strap is correctly affixed, it should remain in place throughout the handling of sensitive electronic components.

Antistatic Mats

Enhancing wrist strap protection is achieved through the use of antistatic matting. These mats are crafted from conductive materials and are strategically placed in work areas, providing an additional layer of defense against ESD by establishing a path for static charges to dissipate easily:

Position the Mat: Place the antistatic mat on the work surface where you will be handling components.
Ground the Mat: Connect one end of the mat to a suitable grounding point using an ESD grounding cord or wire. Ensure that the grounding point is effective and offers a direct pathway to the Earth’s ground.
Ensure Complete Coverage: Verify that the antistatic mat fully covers the entire work area, safeguarding all components from the effects of ESD.

Temperature and Humidity Control

Humidity can lead to issues such as water absorption by circuit boards, component corrosion, and circuit board short circuits. Conversely, dry environments can foster static electricity and result in electrical breakdowns. Therefore, PCBA companies must implement necessary measures to control the humidity and temperature of the production workshop:

Dehumidifiers and Humidifiers: Depending on the local climate, employ dehumidifiers to reduce humidity levels or humidifiers to increase humidity in the work area. Maintaining a humidity range of 40 to 60 percent is considered safe for electronic components.
Storage Conditions: When storing sensitive components, ensure they are kept in controlled conditions with precise humidity levels. Utilize bags containing desiccants to absorb any existing moisture.
Acclimatization: Before commencing assembly work, allow sensitive components time to acclimatize to the controlled environment. This step helps prevent the adverse effects of temperature and humidity variations.
Avoiding Condensation: Prior to removing components from antistatic bags, allow them to reach the temperature of the workstation. This precaution minimizes the risk of condensation.

Avoiding Physical Damage

In PCBA, even a small mistake can result in irreversible damage to the components, necessitating desoldering components for circuit board repairs. To prevent such issues, operators are required to:

Careful Handling: While automated SMT assembly is prevalent, manual handling is unavoidable for prototyping projects or through-hole assembly. Ensure delicate handling of component pins to prevent bending or damage.
Avoid Excessive Force: Components should fit smoothly into their designated slots. If encountering resistance, double-check the orientation and position to avoid using excessive force during insertion or removal.
Prevent Drops: Take precautions to prevent sensitive components from falling or colliding with hard surfaces. If the application environment involves potential impacts, consider conducting a drop test after assembly.

Soldering Sensitive Electronic Components

Right Soldering Equipment

Soldering aims to establish a permanent and strong solder joint between the component and the PCB. This process involves the use of heating equipment and demands extra care and precision to prevent damage and ensure connection quality. The use of precise tools is the initial step in ensuring accurate component soldering. Having a high-quality soldering station with various temperature profiles is crucial. Components with small leads and thermal sensitivity necessitate lower soldering temperatures to reduce thermal stress and potential damage.

When working with sensitive components in light of the trend toward lead-free electronics, it is important to consider unique Lead-free PCB assembly needs. Lead-free solder needs a high temperature for accurate melting, making it important to manage the soldering process to minimize damage.

Right Soldering Technique

For hand soldering, this manual soldering process is used for small-scale PCBA production, prototype or rework. A soldering iron with a tip is employed to melt the solder and create a connection between the component and the board pad. This soldering method demands expertise and precision to prevent component damage or board overheating. It is primarily employed for specialized soldering tasks such as connectors, wire bonding, or discrete components.

In high-volume PCB assembly, automated soldering equipment like wave soldering or reflow soldering comes into play. In SMT assembly, small and sensitive components are directly placed on the PCB’s surface, typically employing reflow soldering. On the other hand, through-hole assembly involves inserting component pins into holes on the board and soldering the pins on the opposite side of the board, usually through wave soldering.

Furthermore, selective soldering is a more recent technique that can be applied to specific components on the board without impacting previously connected components. This method is utilized when certain components cannot withstand the high temperatures of traditional reflow soldering. Selective soldering machines are programmed to heat specific points on the board where soldering is required. The process includes preheating the board and directing a focused stream of molten solder onto the designated component.

Avoiding Overheating

During the soldering process, heat-sensitive components are susceptible to damage from excessive heat. Prolonged exposure to high temperatures can lead to component degradation, thermal stress, and ultimately destruction.

Utilize a soldering iron with temperature control and set it to the appropriate value for the specific component.
Minimize the time the soldering iron tip is in contact with the component leads.
For large-sized components or those with heat-sensitive parts, employ heat sinks or heat shields to prevent direct heat exposure to vulnerable areas.

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