### Introduction to Circuit Board Soldering
Circuit boards, PCBs, and PCB soldering technologies have seen significant advancements in recent years, particularly with the rise of reflow soldering techniques. In principle, traditional through-hole components can also be soldered using reflow methods, commonly known as through-hole reflow soldering. This approach offers the advantage of completing all solder joints simultaneously, thereby reducing production costs. However, the use of temperature-sensitive components can limit the application of reflow soldering, whether they are interposers or SMDs. Consequently, attention has shifted towards the selection of soldering methods. In most applications, selective soldering can be employed following reflow soldering, providing a cost-effective and efficient solution for completing the remaining through-hole components while remaining fully compatible with future lead-free soldering initiatives.
1. **The Solderability of Circuit Board Holes Affects Welding Quality**
Poor solderability of circuit board holes can lead to soldering defects, negatively impacting the performance of components within the circuit. This can result in unstable connections among multi-layer board components and inner wires, ultimately causing circuit failure. Solderability refers to the ability of a metal surface to be wetted by molten solder, resulting in the formation of a relatively uniform and continuous smooth adhesion layer on the metal surface where the solder is applied. The primary factors influencing the solderability of printed circuit boards include:
Here’s a refined version of your article, maintaining clarity and technical accuracy:
(1) The composition and characteristics of solder play a crucial role in the soldering process. Solder, integral to the welding chemical treatment, consists of chemical materials that include flux. Common low-melting eutectic alloys are Sn-Pb or Sn-Pb-Ag. The impurity content must be carefully controlled to prevent oxides formed by impurities from being dissolved by the flux. The flux serves to enhance the solder’s ability to wet the surface of the circuit being soldered by facilitating heat transfer and removing oxidation. Typically, white rosin and isopropanol solvents are used.
(2) The welding temperature and the cleanliness of the metal surface significantly influence weldability. Excessively high temperatures can accelerate solder diffusion, leading to high reactivity that rapidly oxidizes both the circuit board and the molten solder surface, resulting in soldering defects. Contaminants on the circuit board surface also adversely affect solderability, causing issues such as tin beads, tin balls, open circuits, and poor gloss.
(3) Warpage-related welding defects can occur during the soldering process, leading to issues like cold joints and short circuits due to stress-induced deformation. Warpage is often a result of temperature imbalances between the top and bottom surfaces of the circuit board. In large PCBs, warpage can also arise from the weight of the board itself. For standard PBGA devices, which are typically about 0.5 mm above the printed circuit board, any larger components can put the solder joints under prolonged stress as the board cools. A mere 0.1 mm rise in the component height can lead to open circuit conditions.
(4) The design of the circuit board significantly impacts welding quality. When the circuit board is oversized, while soldering may seem more manageable, longer printed traces increase impedance, reduce noise immunity, and raise costs. Mutual interference, such as electromagnetic interference, can also become a concern. Therefore, optimizing PCB design is essential: (1) Minimize wiring between high-frequency components to reduce EMI interference. (2) Heavier components (over 20g) should be secured with brackets before soldering. (3) Address heat dissipation for heat-generating components to avoid defects from large temperature differentials (ΔT) on their surfaces, keeping thermal components distant from heat sources. (4) Arrange components as parallel as possible, enhancing aesthetics and facilitating soldering, thus benefiting mass production. The circuit board should be designed as a 4:3 rectangle, maintaining consistent trace widths to prevent discontinuities. Prolonged heating can cause copper foil to expand and delaminate, so it’s advisable to avoid extensive copper foil areas.
Circuit boards, PCBs, and PCB soldering technologies have seen significant advancements in recent years, particularly with the rise of reflow soldering techniques. In principle, traditional through-hole components can also be soldered using reflow methods, commonly known as through-hole reflow soldering. This approach offers the advantage of completing all solder joints simultaneously, thereby reducing production costs. However, the use of temperature-sensitive components can limit the application of reflow soldering, whether they are interposers or SMDs. Consequently, attention has shifted towards the selection of soldering methods. In most applications, selective soldering can be employed following reflow soldering, providing a cost-effective and efficient solution for completing the remaining through-hole components while remaining fully compatible with future lead-free soldering initiatives.
1. **The Solderability of Circuit Board Holes Affects Welding Quality**
Poor solderability of circuit board holes can lead to soldering defects, negatively impacting the performance of components within the circuit. This can result in unstable connections among multi-layer board components and inner wires, ultimately causing circuit failure. Solderability refers to the ability of a metal surface to be wetted by molten solder, resulting in the formation of a relatively uniform and continuous smooth adhesion layer on the metal surface where the solder is applied. The primary factors influencing the solderability of printed circuit boards include:
Here’s a refined version of your article, maintaining clarity and technical accuracy:
(1) The composition and characteristics of solder play a crucial role in the soldering process. Solder, integral to the welding chemical treatment, consists of chemical materials that include flux. Common low-melting eutectic alloys are Sn-Pb or Sn-Pb-Ag. The impurity content must be carefully controlled to prevent oxides formed by impurities from being dissolved by the flux. The flux serves to enhance the solder’s ability to wet the surface of the circuit being soldered by facilitating heat transfer and removing oxidation. Typically, white rosin and isopropanol solvents are used.
(2) The welding temperature and the cleanliness of the metal surface significantly influence weldability. Excessively high temperatures can accelerate solder diffusion, leading to high reactivity that rapidly oxidizes both the circuit board and the molten solder surface, resulting in soldering defects. Contaminants on the circuit board surface also adversely affect solderability, causing issues such as tin beads, tin balls, open circuits, and poor gloss.
(3) Warpage-related welding defects can occur during the soldering process, leading to issues like cold joints and short circuits due to stress-induced deformation. Warpage is often a result of temperature imbalances between the top and bottom surfaces of the circuit board. In large PCBs, warpage can also arise from the weight of the board itself. For standard PBGA devices, which are typically about 0.5 mm above the printed circuit board, any larger components can put the solder joints under prolonged stress as the board cools. A mere 0.1 mm rise in the component height can lead to open circuit conditions.
(4) The design of the circuit board significantly impacts welding quality. When the circuit board is oversized, while soldering may seem more manageable, longer printed traces increase impedance, reduce noise immunity, and raise costs. Mutual interference, such as electromagnetic interference, can also become a concern. Therefore, optimizing PCB design is essential: (1) Minimize wiring between high-frequency components to reduce EMI interference. (2) Heavier components (over 20g) should be secured with brackets before soldering. (3) Address heat dissipation for heat-generating components to avoid defects from large temperature differentials (ΔT) on their surfaces, keeping thermal components distant from heat sources. (4) Arrange components as parallel as possible, enhancing aesthetics and facilitating soldering, thus benefiting mass production. The circuit board should be designed as a 4:3 rectangle, maintaining consistent trace widths to prevent discontinuities. Prolonged heating can cause copper foil to expand and delaminate, so it’s advisable to avoid extensive copper foil areas.
