Interpretation of PCB board production steps and methods

Everyone knows that a PCB (Printed Circuit Board) is the physical realization of a schematic design. However, don't underestimate the complexity involved in this process. While some aspects may seem straightforward, achieving consistent and reliable performance can be quite challenging. What works well in theory may not translate easily into practice, and what others manage to achieve might be impossible for you. So, while it's easy to say "it's just a PCB," creating a high-quality one is far from simple. In the field of microelectronics, two major challenges are handling high-frequency signals and weak signals. The quality of the PCB manufacturing plays a crucial role in determining the final performance. Even with the same schematic and components, different PCBs can produce very different results. So, how do we create a good PCB? Based on our experience, here are some key considerations: **First, clearly define the design goals.** When starting a project, it's essential to understand what kind of PCB you're dealing with. Is it an ordinary board, a high-frequency board, a low-noise signal-processing board, or a combination of all three? For a standard board, proper layout, clean routing, and accurate mechanical dimensions are sufficient. However, if there are long lines or medium-load traces, special attention must be given to reduce signal degradation. Long lines require careful management to prevent reflections, and when frequencies exceed 40MHz, crosstalk between lines becomes a concern. At higher frequencies, wiring length becomes even more critical. According to distributed parameter theory, the interaction between high-speed circuits and their connections is a decisive factor in system performance and cannot be ignored. As gate speeds increase, signal resistance also rises, leading to increased crosstalk. High-speed circuits also tend to consume more power and generate more heat, which needs to be carefully managed. When dealing with millivolt or microvolt-level signals, extra care must be taken. These signals are extremely sensitive and prone to interference from stronger signals. Shielding is often necessary to maintain a good signal-to-noise ratio. Otherwise, the useful signal may be overwhelmed by noise, making it difficult to extract effectively. Testing points should also be considered during the design phase. Their placement and isolation are important, especially for high-frequency or small-signal lines, as they may not be directly measurable with a probe. Other factors such as the number of board layers, component packaging, and mechanical strength should also be considered. Before proceeding to manufacture, it's essential to have a clear design goal in mind. **Second, understand the function of the components and their layout and routing requirements.** Some components have specific layout and routing needs. For example, analog amplifiers used in certain applications require stable power supplies with minimal ripple. The analog section should be kept away from power components. On some boards, the analog amplifier area is shielded to protect against electromagnetic interference. Similarly, high-power chips like GLINK on NTOI boards generate significant heat and require special cooling solutions. If natural cooling is used, the chip should be placed in an area with good airflow, and its heat dissipation shouldn’t interfere with other components. If high-powered devices like horns are installed, their impact on the power supply must be carefully considered. **Third, consider component placement.** One of the first things to consider in component layout is electrical performance. Components that are closely connected should be placed near each other, especially for high-speed lines. The layout should aim for shorter traces, separating power and small-signal sections. In addition to performance, neat and organized placement makes testing easier. The board’s mechanical size and socket positions should also be carefully planned. Grounding and transmission delay times are critical in high-speed systems. Signal line delays significantly affect overall system speed, particularly in ECL circuits. Even though individual ICs may be fast, interconnection delays on the board (e.g., 30cm lines causing 2ns delays) can severely limit performance. For example, shift registers and synchronous counters are best placed on the same board to avoid timing mismatches due to unequal signal delays. If this isn’t possible, clock lines must be equal in length to ensure synchronization. **Fourth, consider wiring.** With the increasing use of high-speed signal lines above 100MHz, understanding transmission line behavior is essential. **Transmission Line** Any long signal path on a PCB can be treated as a transmission line. If the line’s delay time is much shorter than the signal’s rise time, reflections during the signal transition are negligible. Overshoot, ringing, and oscillation won’t occur. For most modern MOS circuits, longer traces (even meters) can be used without distortion. However, for faster logic circuits, especially ultra-fast ECL, trace lengths must be reduced to maintain signal integrity. There are two main methods to prevent waveform distortion on long high-speed lines. TTL uses Schottky diode clamping to control overshoot, reducing back-oscillation. For HCT series devices, combining Schottky clamping with series resistor termination improves performance further. However, at higher bit rates, these methods may not be sufficient due to reflected waves causing severe distortion. In ECL systems, impedance matching is commonly used to control reflections and ensure signal integrity. For slower TTL and CMOS devices, transmission lines aren’t always necessary. But for high-speed ECL, they offer predictable delay and better control over reflections. Five factors determine whether a transmission line is needed: signal edge rate, connection distance, capacitive load, resistive load, and acceptable overshoot and reflection levels. There are several types of transmission lines: - **Coaxial cable and twisted pair:** Used for system-to-system connections. Coax has a characteristic impedance of 50Ω or 75Ω, while twisted pairs are typically 110Ω. - **Microstrip line:** A signal line isolated from the ground plane by a dielectric. Its impedance depends on width, thickness, and distance from the ground. - **Stripline:** A copper strip between two conductive planes, with controlled impedance based on layer thickness, width, and dielectric constant. **Termination Techniques** - **Parallel termination:** A resistor equal to the line impedance is placed at the receiving end for optimal performance. - **Series termination:** A resistor is placed between the driver and the line to dampen overshoot. - **Non-terminated lines:** If the line delay is much shorter than the signal rise time, no termination may be needed. Choosing between parallel and series termination depends on design preferences and system requirements. Parallel termination allows for faster signal transmission, while series termination reduces crosstalk. The choice between double-layer and multi-layer boards depends on frequency and complexity. For clocks above 200MHz, multi-layer boards are preferred. For frequencies above 350MHz, Teflon-based boards are ideal due to lower loss and better performance. Finally, follow these trace design principles: 1. Keep parallel signal lines spaced apart to reduce crosstalk. Use ground lines between closely spaced signals for shielding. 2. Avoid sharp turns; use smooth arcs to minimize impedance mismatch. 3. Calculate trace widths based on impedance formulas. Typical values range from 50–120Ω, with 68Ω being a common balance between speed and power. 4. On double-layer or multi-layer boards, place traces perpendicularly on opposite sides to reduce crosstalk. 5. Separate ground lines for high-current devices like relays or horns to minimize noise. 6. Keep small-signal lines away from strong signals and shield them if possible. By following these guidelines, you can significantly improve the reliability and performance of your PCB designs.

Semiconductor Chip Carrier

Semiconductor Chip Carrier can be divided into thermo-electric modules, and the power electronic substrates.

Thermo-electric modules are plate-like semiconductor cooling devices that work by using the movement of heat when a current flows through the junction of two different metals. Compact, lightweight, and Freon-free, they are used in climate control seats of automobiles, cooling chillers, optical communications, biotechnology, air conditionners, dryers and a variety of consumer electronic products.

Application of Thermo-electric module Manufacturing Technology for Heat Dissipation and Insulation Substrate

Generally, organic and metal substrates are used in the circuit boards of low-power home appliances and computers.
However, alumina, aluminum nitride and silicon nitride substrates are used in heat radiation insulated substrates of power modules that handle high power.

In particular, silicon nitride substrates are attracting attention for use in power modules of inverters and converters because of the increase in sales of HEVs and EVs.

Chip Carrier Package,Ceramic Chip Carrier,Plastic Leaded Chip Carrier,Chip Carrier Socket

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