PCB Materials & Manufacturing Processes Flashcards

What is the primary function of the substrate in a PCB?

Answer: To provide mechanical support and insulation

The substrate in a Printed Circuit Board (PCB) is the non-conductive material, typically fiberglass, that forms the base of the board. Its primary function is to provide rigid mechanical support for all components and copper traces. Additionally, it electrically insulates these conductive elements from each other, preventing short circuits and ensuring proper circuit function.

Which material is commonly used as a substrate in rigid PCBs?

Answer: FR-4

FR-4 is the most widely used and cost-effective material for rigid PCB substrates. It is a glass-reinforced epoxy laminate that provides an excellent balance of electrical insulation, mechanical strength, and thermal stability. This makes it suitable for a vast range of electronic applications, from consumer electronics to industrial equipment.

What is the purpose of solder mask on a PCB?

Answer: To protect copper traces and prevent solder bridging

Solder mask is a protective polymer layer applied over the copper traces of a PCB. Its primary purpose is to insulate the traces, preventing accidental short circuits (solder bridging) during the soldering process. It also protects the copper from oxidation, moisture, and contaminants, ensuring long-term reliability of the board.

Which manufacturing process is used to create PCB copper traces?

Answer: Etching

Etching is the chemical process fundamental to creating PCB copper traces. After a photoresist layer defines the desired circuit pattern, the board is exposed to an etchant solution. This solution selectively dissolves the unprotected copper, leaving behind the intricate network of conductive traces and pads that form the circuit.

What is the main benefit of using a via in PCB design?

Answer: To connect multiple layers electrically

Vias are plated-through holes in a PCB that serve as essential electrical connections between different layers of the board. They allow signals and power to transition vertically through the substrate, enabling the creation of complex multi-layer designs and compact component placement. This is crucial for modern high-density electronics.

What is the role of copper thickness in PCB manufacturing?

Answer: It determines current capacity and resistance

Copper thickness is a critical parameter in PCB manufacturing as it directly influences the electrical performance of traces. Thicker copper allows for higher current carrying capacity and lower resistance, which is vital for power distribution and minimizing heat generation. Conversely, thinner copper is used for fine-pitch signal traces where current demands are low.

Which manufacturing method is used to drill holes for component leads and vias?

Answer: Drilling

Drilling is the precise manufacturing method used to create holes in a PCB. These holes are essential for mounting through-hole components, forming vias for inter-layer electrical connections, and providing alignment features during assembly. High-precision drills or lasers are typically employed to achieve the required accuracy.

Why is thermal management important in PCB manufacturing?

Answer: To prevent overheating and ensure reliability

Thermal management is paramount in PCB manufacturing and design to effectively dissipate heat generated by electronic components. Excessive heat can severely degrade component performance, shorten their lifespan, and even lead to catastrophic board failure. Proper thermal design ensures the PCB operates within safe temperature limits, thereby guaranteeing long-term reliability and functionality.

What is the common finish applied to exposed copper pads to prevent oxidation?

Answer: HASL or ENIG finish

Exposed copper pads on a PCB are highly susceptible to oxidation, which can significantly hinder solderability and create unreliable connections. Surface finishes like Hot Air Solder Leveling (HASL) or Electroless Nickel Immersion Gold (ENIG) are applied to protect these pads. These finishes provide a clean, solderable, and corrosion-resistant surface for component attachment.