PCB holes, or vias, are essential for connecting different layers within a printed circuit board (PCB) and mounting leaded components. They can be categorized into three main types: blind vias, buried vias, and thru-hole vias. Blind vias connect an outer layer to an inner layer but do not go through the entire board. They help save space and enhance heat transfer but are more expensive than thru-hole vias due to their complex manufacturing process. Buried vias connect two or more internal layers without reaching the outer layers, adding to the difficulty and cost of production.
Poor Drilling: Dust left in the holes after drilling, especially in those larger than 0.3mm, can prevent copper from being properly plated during the copper plating process, leading to non-conductive vias. Such defects are usually detected during electrical testing and result in the PCB being scrapped. Copper Plating Defects: Insufficient copper plating time can result in thin hole walls that may dissolve during high-temperature reflow soldering, especially in vias smaller than 0.3mm. For PCBs requiring high current, inadequate copper thickness can cause the copper wall to melt, leading to defects. Designers must specify thick copper plating for high-current boards, such as power supply boards. Unqualified SMT Materials or Technique: Issues may arise from using impure tin, poor-quality flux, or improper SMT techniques, leading to poor soldering, non-functional components, and non-conductive vias, especially in plug-in vias.
To minimize PCB costs, several factors must be considered. The size of the PCB is crucial; smaller boards typically cost less, and following standard sizes can reduce costs further. Surface-Mount Technology (SMT) is less expensive than Through-Hole Technology (THT) due to its more compact design. However, dense component placement requires finer wiring, advanced materials, and careful design to avoid performance issues, which can increase costs.
Capacitors may act as inductors at certain points, rendering them ineffective as decoupling capacitors. Therefore, the expected tolerance of capacitors, such as ±5%, may have unexpected variations, necessitating careful consideration, correction, or calibration, especially for critical frequencies or timings.
Advances in PCB design software have made PCB creation accessible to more people, and online searches can help users find manufacturers, particularly in China, which is the world's largest PCB production base. Shenzhen, a key electronics hub in China, hosts numerous companies capable of quickly designing, manufacturing, and supplying PCBs. Online research is crucial when purchasing PCBs or PCB assemblies (PCBA), as pricing varies among companies. Instant quotes from providers like SysPCB in Shenzhen can help ensure customers receive the desired PCB at a competitive price.
Capacitor performance is significantly affected by manufacturing tolerance binning and soldering stress, especially for surface-mount components. Poor soldering temperature profiles can cause damage, such as the "tombstone effect," where capacitors stand on one end. Following the manufacturer's recommended solder-profile is crucial, as different components may require varying melting points for optimal assembly. Capacitors, while considered passive, exhibit active behaviors due to parasitic elements, tolerances, temperature changes, and aging, which can affect signal integrity, especially in sensitive measurements. Tools from companies like AVX and Kemet, including free Spice tools and application notes, provide valuable resources for understanding these effects and predicting capacitor performance.