{"id":1875,"date":"2026-10-02T09:00:00","date_gmt":"2026-10-02T01:00:00","guid":{"rendered":"https:\/\/www.jingpengpcb.com\/?p=1875"},"modified":"2026-10-02T19:38:00","modified_gmt":"2026-10-02T11:38:00","slug":"impurities-affecting-small-holes","status":"publish","type":"post","link":"https:\/\/www.jingpengpcb.com\/en\/blog\/impurities-affecting-small-holes\/","title":{"rendered":"What Impurities Affect the Quality of PCB Via Holes? Workshop Environment and Improvement Measures"},"content":{"rendered":"

Abstract: This article will discuss the sources of contaminants that affect the quality of small holes in PCB manufacturing and how to address these issues. We will delve deeply into this important topic, focusing on the control of fine contaminants that accumulate over time in metal holes.<\/p>\n

From 1995 to 2026, the capabilities of mechanical drilling have advanced from a minimum hole diameter of 0.4 mm to 0.15 mm\u2014and even smaller. The diameters of metallized holes have also become increasingly smaller, and these holes directly affect the reliability of printed circuit boards.<\/p>\n

\"Mechanical<\/p>\n

Requirements for the Workshop Environment in PCB Manufacturing<\/h2>\n

In PCB manufacturing, the workshop environment and cleanliness are critical to product quality. The following are some specific requirements for the workshop environment in PCB manufacturing:<\/p>\n

1. Temperature and Humidity Requirements<\/h3>\n

To ensure the proper operation of equipment and high-quality production processes, the workshop temperature should be maintained at 23\u00b13 degrees Celsius, and relative humidity should ideally be between 45% and 70%RH. Such an environment helps prevent equipment malfunctions and maintain high standards in production processes.<\/p>\n

2. Ventilation Capacity<\/h3>\n

Reflow and wave soldering equipment generate fumes, so exhaust fans must be installed to remove them. For fully hot-air ovens, the minimum airflow rate in the exhaust duct is typically required to be 14\u201315 m\/min. Proper ventilation helps maintain clean air quality in the workshop and protects the health of workers.<\/p>\n

3. Power Requirements<\/h3>\n

PCB manufacturing equipment requires a stable power supply voltage and power. Typically, single-phase AC 220 V (220 \u00b1 101 TP3T, 50\/60 Hz) or three-phase AC 380 V (380 \u00b1 101 TP3T, 50\/60 Hz) is required. If the power supply is unstable, a voltage regulator must be installed, and the power supply capacity should exceed the equipment\u2019s power consumption. Additionally, SMT placement machines require a dedicated ground connection to minimize electromagnetic interference, as the high operating speeds of these machines may affect the normal operation of other equipment and compromise placement accuracy.<\/p>\n

4. Electrostatic Protection Requirements<\/h3>\n

Static electricity can cause damage during PCB production, so static electricity protection is crucial. Employees entering the workshop must wear antistatic work clothes and caps, put shoe covers over their shoes, and wear antistatic wrist straps. These measures help minimize the impact of static electricity on PCBs.<\/p>\n

Quality Issues with Small Holes and Foreign Matter Control<\/h2>\n

1. Mechanism of Pore Formation<\/h3>\n

Drilling and Chemical Processing in PCB ManufacturingElectrolytic Copper Plating<\/a>This is a critical step. Drilling is performed on bare holes, which are then converted into conductive plated-through holes through chemical copper plating. Chemical copper plating and electroplating are important steps in metallizing the holes.<\/p>\n

1.1 Mechanism of Chemical Copper Deposition<\/h4>\n

When manufacturing double-sided and multilayer PCBs, it is necessary to convert non-conductive bare vias into conductive ones, which requires electroless copper plating. This is a catalytic \u201coxidation\/reduction\u201d reaction in which copper is deposited in a chemical solution through the catalytic action of metal particles.<\/p>\n

1.2 Mechanism of Copper Electroplating<\/h4>\n

Electroplating is a process that uses an electrical current to deposit positively charged metal ions onto the surface of a conductor to form a coating. Copper electroplating is also an \u201coxidation\/reduction\u201d reaction, achieved by oxidizing the metal surface and then reducing copper ions to form metallic copper.<\/p>\n

2. Debris clogging the hole<\/h3>\n

Over the course of long-term production, it was found that when the pore size reached 0.15\u20130.3 mm, the proportion of clogged pores increased by 30%.<\/p>\n

2.1 The Problem of Pore Blockage During Pore Formation<\/h4>\n

In printed circuit board manufacturing, mechanical drilling is still the most common process used for small holes ranging from 0.15 to 0.3 mm. Long-term inspections have revealed that impurities left in the holes during drilling can cause plating failures. Some possible causes of hole plugging include:<\/p>\n