1. PCB circuit board term “Acceleration” (through-hole plating, chemical copper, direct plating) broadly refers to various chemical reactions that can be expedited by the addition of certain accelerators. More specifically, it pertains to the plated through hole (PTH) process, where, after an activation reaction, the outer layer of the adsorbed palladium colloid is stripped using an acid (such as sulfuric acid or a fluorine-containing acid) in a rapid bath. This exposes the active palladium metal, allowing it to directly interact with copper ions and resulting in the formation of a chemical copper layer before the subsequent treatment.

2. Accelerator, or accelerator (through-hole plating, chemical copper, direct plating), denotes additives that can enhance chemical reactions. In PCB terminology, this term can sometimes be used interchangeably with “Promoter.” During the impregnation of resin, a specific accelerator plays a role in its A-stage. In the PTH process, when the tin-palladium colloid settles on the pore wall of the substrate, it is essential to dissolve the outer tin shell with an acid, enabling direct interaction between the palladium and the chemical copper agent.

3. Activation (through-hole plating, electroless copper, direct plating) generally refers to the state of excitement necessary for initiating a chemical reaction. More narrowly, it describes the process wherein palladium colloids deposit on the walls of non-conducting holes during the PTH process. The solution used in this step is known as the Activator. A related term, “Activity,” denotes the concept of “activity.”

4. Activator (through-hole plating, chemical copper, direct plating) in the PCB industry typically refers to the activating agents found in flux, such as inorganic zinc chloride or ammonium chloride, as well as organic hydrohalogenated amines or organic acids. These substances assist in the cleaning process of the welded metal surface at high temperatures, often referred to as “pinoleic acid.” Collectively, these additives are called Activators.


5. BackLight (BackLighting) is a method for inspecting the integrity of plated through-hole copper walls through magnified visual examination. This technique involves carefully thinning the substrate outside the hole wall from a specific angle to get close to the hole wall, followed by injecting light from the thin substrate on the back, utilizing resin translucency. If the chemical copper hole wall is intact without any holes or pinholes, the copper layer should block light, appearing dark under a microscope. Conversely, any hole in the copper wall will reveal a light spot, which can be enlarged and documented, known as the “backlight inspection method” or ThroughLightMethod, though it only allows visibility of half the hole wall.

6. Barrel hole wall refers to the hole wall of PTH on circuit boards, often indicating issues like BarrelCrack, which signifies a broken copper wall. In the electroplating context, “barrel plating” describes the process where numerous small parts are placed in a rotatable barrel, allowing them to touch and overlap with soft parts inside. A conductive cathode rod is connected, and during operation, the small parts are electroplated while rolling vertically. The voltage used in this barrel plating method is approximately three times greater than that of conventional electroplating.

7. Catalyst refers to an additional “introducer” added to each reactant prior to a chemical reaction to facilitate the required reaction smoothly. In the circuit board industry, it specifically pertains to the PTH process where the “palladium chloride” bath “activates and catalyzes” non-conductive plates, promoting the growth of seeds for electroless copper coating. This academic term is often colloquially referred to as “Activation” or “Nucleating,” with “catalyst” being the accurate translation.

8. Chelate, in some organic compounds, refers to the redundant “electron pairs” on adjacent atoms that can form rings with foreign divalent metal ions (like Ni2+, Co2+, Cu2+, etc.), akin to how a crab’s claws hold onto an object. Such compounds are termed Chelating Agents, with common examples including EDTA (ethylenediaminotetraacetic acid) and ETA.

9. Circumferential Separation describes the plated through-hole copper wall’s functionality in providing soldering and inter-layer interconnection (Interconnection). The integrity of the hole wall is crucial; ring-shaped holes may arise from insufficient PTH, poorly covered tin and lead plating, or corrosion, reflecting significant quality deficiencies.

10. Colloid refers to a type of fluid classification, exemplified by substances like milk and muddy water, which consist of large or small molecules suspended in a liquid. Unlike true solutions, colloids maintain this suspended state. The “palladium” in the PTH activation bath starts as a true solution but transitions to a colloidal state upon aging, necessitating the colloidal bath for the activation reaction.

11. Direct Plating is an innovative process that has emerged recently, aiming to eliminate traditional chemical copper containing harmful formaldehyde from PTH. It prepares the hole wall for metalization (through methods like black hole, conductive polymer, and electroplating chemical copper) and directly electroplates copper to complete the hole wall, with various commercial processes currently being promoted.

12. EDTA stands for Ethylene-Diamine-Tetra-Acetic Acid and serves as a significant organic chelating agent. This colorless crystal is slightly water-soluble, and its four dissociable hydrogen atoms can be replaced by sodium atoms to form various sodium salts, enhancing its solubility. Post-hydrolysis, it captures divalent metal ions in water, functioning as “chelating” clips. EDTA has extensive applications, including in cleaning agents, shampoos, chemical copper and electroplating, antioxidants, heavy metal detoxifiers, and other pharmaceuticals, making it a crucial additive.

13. Electroless-deposition, or electroless plating, occurs in a bath of metal ions (like copper or nickel) where a negatively charged surface is submerged, allowing for continuous metal deposition without external current. This process, predominant in the circuit board industry, is often referred to as “non-electric copper” or “chemical copper,” sometimes called “sink copper” in mainland terminology.