Printed circuit board assembly, or PCBA, usually involves many methods. Soldering is one of the most critical steps, making strong electrical and mechanical links between PCB parts. However, when making PCBAs, the two main choices are lead and lead-free solder.
Lead solder was discovered many years ago. However, due to its risk of health hazards in the workplace, people came up with different solutions, like lead-free soldering. In today’s world, both soldering methods are used, but lead-free soldering is more common.
This article explains lead and lead-free solder manufacturing in PCBAs. It typically briefly introduces how these two soldering methods are used in a PCB factory. We hope this article can help you choose the correct soldering method for your project.
Lead and Lead-free Solder Manufacturing Procedure in PCBA
Both lead and lead-free solder manufacturing have their unique pros and cons. They find different applications for different electronic gadgets based on these pros and cons. Consequently, when you decide between these two, you must assess “lead vs. lead-free solder.” And then evaluate your project needs. Finally, balance your project needs with the pros and cons of these two soldering methods.
What is Lead Soldering?
Lead soldering is also called as SnPn solder. Here, Sn denotes Tin, and Pb denotes lead. In the construction, Sn or Tin acts as the base metal. However, the quantity of the Sn and Pb may vary. The most popular composition, in this case, is Sn37Pb. The melting temperature of lead solder (Sn37Pb) is 183°C.
Benefits of Lead Solder Manufacturing
(1) Lead solder is ductile and very easy to work with.
(2) Leaded solder offers very high electrical conductivity.
(3) This soldering method is reliable for high-performance applications.
(4) Lead soldering has a comparatively lower melting point. Also, the cooling of lead solder is faster than lead-free soldering. Therefore, you may find fewer connection problems on your PCB.
Limitations of Lead Solder Manufacturing
(1) The lead solder method is not environmentally friendly. RoHS regulations restrict it.
(2) Since lead soldering is ductile, thus it is not as durable as lead-free soldering.
Lead Soldering Manufacturing Procedure in PCBA
The lead solder manufacturing procedure in PCBA is simple. First, you must prepare the lead solder paste and apply it to the PCB pads. Then, carefully place the components on the board. Then, heat the board. In this case, you can use wave or reflow soldering techniques.
The heat causes the lead solder paste to melt, creating secure connections. Once cooled, the solder solidifies, making a proper electrical pathway.
What is Lead-Free Soldering?
Lead-free soldering, on the other hand, doesn’t use lead. It is typically made of alloys based on Tin (Sn) with a small quantity of different alloys. In this case, the popular alloys are silver, copper, zinc, and indium. There are various alloys as well. However, the exact alloy use depends on the specific specifications of the final electronic gadget.
A common type of lead-free soldering is SAC387. The melting point of this lead-free solder is 217°C.
Benefits of Lead-free Solder Manufacturing
(1) Lead-free soldering is environmentally friendly. It goes with the standard RoHs-complaint.
(2) This soldering method is much more durable than lead soldering. The alloy improvements allow you to control the joint strength.
(3) This soldering method is highly suitable for modern consumer electronics.
(4) Lead-free solder manufacturing reduces the contamination risk, making this method much safer for workers.
Limitations of Lead-free solder Manufacturing
(1) Lead-free soldering has a higher melting point (SAC387 217°C). Also, it has a slower cooling rate. Because of this, the manufacturing must be controlled and correctly observed. Otherwise, you may find various connection problems.
(2) Lead-free solder shows worse wettability than lead soldering. This means it doesn’t spread as quickly as lead solder when melted. Because of this, lead-free solder struggles to form strong and reliable connections.
(3) This soldering method is typically more expensive than lead soldering.
(4) Lead-free solder contains high tin content, which can cause tin whiskers, metal dendrites, CAF, and tin pest
Lead-Free Manufacturing Procedure in PCBA
Lead-free soldering also follows a systematic approach. First, prepare the lead-free solder paste and apply it to PCB pads. Then, you can place various components on the PCB. Once you are done placing components, you can heat the board using the reflow soldering technique. As the solder cools, it forms durable electrical connections.
Is there any difference between lead and lead-free soldering manufacturing procedures in PCBA? Yes, there are. First, lead-free soldering requires higher reflow temperatures, which require more precise management.
Unleaded soldering methods are used for many things these days. This method helps various uses, such as computers and smartphones, meet diverse needs. This technology is also used a lot in other communication gear. Medical tools, cars, and even the aerospace business use lead-free soldering. Most electronics use lead-free soldering because it is safe and doesn’t break any rules about RoHS.
Lead vs Lead-Free Solder: Which is Better?
You are already familiar with the pros and cons of both lead and lead-free soldering manufacturing in PCBA. Now, you realize that the right option typically depends on your application.
Lead soldering offers better conductivity and a lower melting point. On the other hand, lead-free soldering is environmentally friendly and also very durable. So, the choice typically depends on the final product.
Lead vs Lead-Free Solder: Wettability
Lead soldering offers higher electrical conductivity. It is very suitable for strong signal transmission. On the other hand, lead-free soldering cannot provide you with such conductivity, but near the ranges. It is also used in many high-frequency electronic gadgets. Check the alloy composition before you decide on the type of solder paste.
Lead vs Lead-Free Solder: Melting Point
Lead solder has a lower melting point. Because of this, these solder joints reduce thermal stress on components. On the other hand, lead-free solders need higher temperatures, which may affect heat-sensitive parts.
Lead vs Lead-Free Solder: Durability and Compliance
Lead solders are easier to work with, but they are ductile. These solder joints cannot offer high durability. Also, this soldering technique is restricted due to environmental concerns.
On the other hand, lead-free solder is more durable due to alloy reinforcement. Besides, these solder joints comply with the RoHS regulations.
Lead vs Lead-Free Solder: Application Suitability
Lead solder is ideal for applications where a high-quality signal is necessary. Typical examples include telecommunications, aerospace, military, and many legacy systems. On the other hand, lead-free solder is best for consumer electronics, medical devices, and more.
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