Electronic and electromechanical components rely on electrical contacts to function. The process of establishing electrical connections between two separate contacts is called interconnection. In order to fulfill a device’s intended function, electronic components must be interconnected in alignment with the schematic circuit diagram.
A printed circuit board (PCB) is a fundamental part of an electronic device, but it alone cannot form a complete product. External connections are necessary to connect PCBs to each other, to external components, and to equipment panels. Selecting the most suitable interconnection method is crucial in PCB design, balancing reliability, manufacturability, and cost-effectiveness. There are various methods for external connections, and the choice should be made based on the specific requirements of each case.
### Interconnection Methods for Circuit Boards
#### 1. Soldering Method
The soldering method is one of the most widely used techniques for interconnecting components on a PCB. Its main advantages are simplicity, low cost, and high reliability. This method is particularly effective in preventing failures due to poor contact, ensuring that the electrical connections remain stable over time.
However, soldering does have some drawbacks. The main issue is that it makes interchangeability and maintenance more difficult, as components are permanently fixed to the board once soldered. This method is generally most suitable for components with fewer external leads, where the connections do not require frequent adjustments or replacements.
In conclusion, while soldering is a cost-effective and reliable interconnection method, it is best suited for static, low-maintenance applications where long-term stability is prioritized over flexibility.
### 1. PCB Wire Soldering
PCB wire soldering involves connecting components or external parts directly to the PCB using wires, without the need for connectors. This method is commonly used for connecting devices like the speaker and battery box in radios.
**Key considerations for PCB wire soldering:**
– **Pad Placement and Size:** Solder pads should be positioned as close as possible to the edge of the PCB and should be of uniform size. This ensures ease of soldering and simplifies future maintenance or repair tasks.
– **Improved Mechanical Strength:** To avoid pad or trace damage from wire tension, it is important to reinforce the solder joints. This can be achieved by drilling small holes near the soldering pads, allowing the wire to pass through and be soldered on the component side. This through-hole technique enhances the connection’s mechanical durability.
– **Wire Management:** Proper wire routing is essential to prevent breakage or disconnection. Wires should be neatly arranged and secured using wire clips or other fastening methods to minimize movement and ensure long-term reliability.
### 2. PCB Cable Soldering
In this method, a flat cable connects two PCBs, offering a reliable and error-free connection. The position of the two boards remains flexible, and the relative orientation of the boards can vary.
This method is particularly useful when connecting two PCBs at a 90-degree angle, resulting in a combined, rigid assembly once the connection is completed.
### 3. Connector-Based PCB Interconnection
In more complex electronic systems, connectors are commonly used for interconnecting PCBs. This modular “building block” structure provides several advantages, including:
– **Mass Production Efficiency:** Connectors allow for easier assembly and quality control, lowering overall production costs.
– **Simplified Maintenance:** When failures occur, maintenance personnel do not need to diagnose issues at the component level. Instead, they can quickly identify faulty boards and replace them, reducing downtime and improving system uptime. Faulty boards can be repaired and stored as spares, allowing for faster troubleshooting and system restoration.
**Two common methods of connector-based PCB interconnection:**
#### 1. PCB Printed Board Socket Connection
This method is frequently used in complex devices. A printed plug is designed at the edge of the PCB, which fits into a corresponding socket. The socket’s design depends on various factors, including the number of contacts, pin spacing, and positioning holes. The plug section of the PCB is often gold-plated to improve wear resistance and reduce contact resistance.
**Advantages of this method:**
– **Ease of Assembly:** The connection is simple to assemble and offers good interchangeability, making it suitable for mass production.
– **Maintenance-Friendly:** Faulty boards can be quickly replaced, improving overall system maintainability.
**Disadvantages:**
– **Cost and Precision:** This method increases the cost of manufacturing and requires precise PCB design and fabrication.
– **Reliability Issues:** The contact areas (plug and socket) may suffer from oxidation or wear over time, reducing the connection’s reliability. To address this, it is common to use parallel wire leads or multiple contacts to improve the connection’s integrity.
Socket connections are typically used in multi-board systems and come in two main types: **reed-type** and **pin-type**, each offering different mechanical properties for interconnecting PCBs.
#### 2. Standard Pin Connection
Standard pin connections are commonly used for external connections in smaller instruments. The two PCBs are connected through standard pins, which are typically arranged either parallel or perpendicular to each other.
**Benefits of pin connections:**
– **Simplified Mass Production:** Standard pins allow for easy and cost-effective assembly, making this method ideal for smaller devices that require high-volume production.
In summary, the choice of interconnection method—whether wire soldering, cable soldering, or using connectors—depends on the complexity, durability requirements, and production scale of the electronic device. Each method has its own advantages and limitations, and understanding these trade-offs is essential for designing reliable and efficient PCB systems.
