Lead Hazards in PCB Manufacturing: Risks and Solutions

I The Dangers of Lead

Lead has been used in various industries for over a thousand years. It is also used in the production of PCB (Printed Circuit Board) boards. Currently, the global annual usage of lead is approximately 5 million tons. Among this, 81% is used in batteries. The next largest uses are in lead oxide white paints and weapons, each accounting for about 10%. These three are the main destinations for large amounts of lead. In fact, the amount used in circuit board production and the soldering industry for electronic products is only 0.49%. However, because it is spread over such a wide range and is very difficult to recycle and reuse, the pollution and harm it causes cannot be considered minor. The dangers of lead are evident from this.

Table 1: Global Lead Usage Distribution by Industry

Industry	Percentage	Annual Usage (tons)
Batteries	81%	4,050,000
Lead Oxide Paints	10%	500,000
Weapons	10%	500,000
PCB & Electronics Soldering	0.49%	24,500
Other Uses	-1.49%	-74,500
Total	100%	5,000,000

Blood Lead Concentration vs. Health Impact

Lead is a "killer" of cells. When the blood lead concentration reaches 15 mg per 100 ml, it can cause delayed development and reduced intelligence in children. Moreover, the younger the child, the more severe the nerve damage. Lead poisoning manifests as excessive movement, excitability, poor sleep, loss of appetite, frequent urination or bedwetting, irritability, mood swings, and even poor hearing and language expression abilities. The dangers of lead are very terrible, so the shift to lead-free production in circuit board manufacturing is urgent.

The Dangers of Lead in PCBA Blood

Lead compounds easily seep into groundwater, which becomes a potential crisis for drinking water. Take Japan as an example: its environmental protection regulations require that lead in groundwater must not exceed 0.3 ppm (0.3 mg/l). As for the United States, in its EPA 40 CFR 141, the limit for lead in drinking water is even stricter, with an upper limit of only 15 ppb (0.015 mg/l). According to the TCLP toxicity leaching test in the U.S. Environmental Protection Agency's EPA 40 CFR 261, the maximum leachable amount of lead can only be 5 mg/l. However, the amount of lead that leaches from various solder joints in general circuit board production when they are discarded in nature is hundreds of times higher than the leaching amount in the above test. The danger of lead is so great—how can it not make people cautious and fearful? Therefore, the shift to lead-free production in the manufacturing of circuit boards for electronic products is imperative.

Table 2: Lead Limits in Drinking Water (Global Standards)

Region/Standard	Maximum Allowable Lead	Regulation Reference
Japan	0.3 ppm (0.3 mg/l)	Environmental Protection Regulations
United States	15 ppb (0.015 mg/l)	EPA 40 CFR 141
EU (Drinking Water Directive)	10 ppb (0.01 mg/l)	EU Drinking Water Directive
TCLP Toxicity Test	5 mg/l	EPA 40 CFR 261

Lead and Lead-Free Solder in PCB Manufacturing

Lead solder (also known as SnPb solder) is a metal alloy with lead (Pb in the periodic table) and tin (Sn in the periodic table) as its basic components. Many years ago, the use of lead pipes and any water supply pipes connected with lead solder was banned in new U.S. plumbing systems. Soon after, the occupational risks of lead soldering were also considered, and lead-based solder became a documented health hazard in the workplace. The dust and fumes generated by lead soldering operations are considered toxic when inhaled.

For these reasons, lead solder continues to be phased out due to its negative impact on the environment and health. Lead-free solder is a substitute for traditional 60/40 and 63/37 SnPb solders. In 2006, the European Union (EU) adopted the Restriction of Hazardous Substances (RoHS) directive. The United States followed, offering tax breaks to any company that reduces the use of lead-based solder. Today's lead-free solder formulations have different percentages of the following:

Common Lead-Free Solder Components

Copper (Cu)
Tin (Sn) – Primary component
Silver (Ag) – Improves strength
Nickel (Ni) – Enhances durability
Zinc (Zn) – Aids in flow
Bismuth (Bi) – Lowers melting point
Antimony (Sb) – Increases hardness

Key RoHS Compliance Dates

1 2006 – EU RoHS 1 goes into effect
2 2011 – First major RoHS revision
3 2019 – RoHS 2 enforcement加强
4 2021 – Global adoption exceeds 85%

The ultimate goal is to select high-quality solder alloys that, when combined with other trace metals, will achieve excellent mechanical properties.

Comparing Lead and Lead-Free Solder Paste

When considering soldering temperatures, this depends on the alloy combination and quality. But generally, 60/40 tin/lead solder turns liquid at 361°F. The higher the tin content, the higher the melting point and the higher the product cost. Lead-tin solders are easier to use; they flow well and can reach working temperatures more quickly.

However, in terms of safety, lead-containing solders carry significant risks and can only be used when permitted by regulatory authorities. They must also be disposed of properly. Lead is harmful to the environment, toxic to the body, and there is a risk of it being quickly absorbed into the blood.

Lead-free solder paste melts at a higher temperature, around 422°F. Although higher temperatures require changes in soldering methods, joints soldered with lead-free solder paste have proven to be reliable.

Because lead-free solder paste has poorer wettability than lead-containing solder, the appearance of solder joints will be different.

Is Your PCB Made with Lead-Free Process? How to Tell?

PCBASAIL has long strongly recommended lead-free boards to ensure the production of green products. What exactly makes a board lead-free, and how can we tell if a PCB is made with a lead-free process?

Appearance Check

Leaded solder has a bright white surface. Lead-free solder appears pale yellow due to its copper content. This color difference is one of the easiest ways to distinguish between the two.

Touch Test

Rub your finger over the solder: lead-free solder leaves a pale yellow mark, while leaded solder leaves a black mark. Always wash hands after this test.

Composition Analysis

Leaded solder contains tin and lead. Lead-free solder has < 500 PPM lead, with main components like tin, silver, or copper. "Lead-free" means trace amounts, not zero.

Usage Matching

Leaded solder is used with leaded components and tools. Lead-free processes require compatible lead-free components to maintain compliance.

From a usage perspective, leaded solder is used for soldering leaded products, and the tools and components used are all leaded. With the introduction of these aspects, you can clearly and quickly identify whether a PCBA board uses lead-free soldering when you encounter it.

Differences Between Leaded and Lead-Free PCBs

1 Solderability

The melting point of the lead-free process is 218 degrees, while the melting point of leaded hot air solder leveling is 183 degrees. The solderability of lead-free solder is higher than that of leaded solder. Leaded processes have relatively poor firmness, and soldering is prone to cold solder joints. However, because the temperature of leaded processes is relatively low, there is less thermal damage to electronic products, and the PCB surface is brighter.

2 Cost Differences

In lead-free processes, the tin bars used in wave soldering and the tin wires used in manual soldering increase costs by about 3 times. The cost of solder paste used in reflow soldering increases by about 2 times.

Material/Process	Leaded Cost	Lead-Free Cost	Cost Increase
Wave Soldering Tin Bars	$X	$3X	+200%
Manual Soldering Tin Wires	$Y	$3Y	+200%
Reflow Soldering Paste	$Z	$2Z	+100%

3 Safety

Lead is a toxic substance. Long-term use causes harm to human health and the environment.

Even though leaded processes have advantages such as lower prices and brighter surfaces, in recent years, under the pressure of environmental protection policies, the space for leaded processes has been shrinking. The main reason is that the wastewater discharge from leaded PCB processes, and when leaded PCB products are discarded, whether disposed of by burial or incineration, lead will eventually return to the environment through various media, causing serious lead pollution and great harm to the environment and human survival.

How PCBASAIL Prevents Lead Hazards

Lead-free solder wire is obviously safer than leaded solder wire. But even with lead-free solder wire, safety protection must be paid attention to during use. In addition, during soldering, the flux in the solder wire comes into contact with the high-temperature soldering iron, vaporizes, and forms fumes. These fumes contain rosin and chemical raw materials. Long-term inhalation may cause adverse effects on the human body. Therefore, the main hazard to guard against during soldering is lead fumes. Even when using lead-free solder, it may contain trace amounts of lead. Although lead-free solder has less impact than leaded solder, we must guard against the smallest risks. It is essential to use solder wire that meets standards and take appropriate protective measures to ensure health.

At the same time, we should also realize that although lead-free solder wire has less impact on the environment and the human body than leaded solder wire, it still contains a certain amount of lead and is not completely harmless. Therefore, when using a soldering iron for soldering, it is crucial to choose tin wire that meets RoHS standards and take effective preventive measures to ensure the safety of the operation process.

Essential Safety Measures

Wear gloves, masks, or gas masks during soldering to reduce lead fume inhalation.
Ensure good ventilation in the workplace to lower airborne lead concentrations.
Thoroughly wash hands and face after work to remove any lead residue on the skin.
Schedule reasonable work breaks (e.g., 15 minutes after 1 hour of work) to reduce physical strain.
Adopt healthy habits: reduce smoking and drink plenty of water to help flush toxins from the body.

Arrange work hours reasonably. Avoid working continuously for long periods. For example, resting for 15 minutes after working for 1 hour helps reduce physical strain. In addition, developing other good living habits also helps prevent the hazards of lead fumes. For example, reducing smoking frequency and drinking more water to promote the excretion of toxins from the body. Good living habits, such as quitting smoking and drinking more water, can help reduce the health hazards caused by lead fumes.