Jun. 17, 2024
With the continuous development of the electronics industry, the technical level of PCB is also rising. Common surface treatment technology include HASL(Lead Free HASL and HASL), immersion gold, gold plating, OSP, etc. HASL is to coat a layer of tin-lead alloy on the copper surface to prevent the copper surface from being oxidized, and then provide a good soldering base for subsequent assembly. Do you know the difference between lead free HASL and HASL?
Contact us to discuss your requirements of lead-free hasl. Our experienced sales team can help you identify the options that best suit your needs.
1. Lead-free HASL belongs to environmentally protection process and does not contain harmful substances "lead"; HASL is not an environmentally protection process and contains harmful substance "lead", which is harmful to human body for long-term use.
2. The lead content of lead free HASL shall not exceed 0.5, but the lead content of HASL shall reach 37.
3. From the surface of the tin, HASL is brighter and lead-free HASL is darker; The wettability of HASL is better than lead free HASL.
4. Lead will increase the activity of the tin solder wire during the soldering process. Compared with the lead free solder wire, the lead-containing solder wires is easier to use. Lead-free HASL has a higher melting point than HASL, and the solder joints will be much stronger.
5. The melting point of lead free HASL is about 218 degrees, the temperature of the tin stove needs to be controlled at 280-300 degrees, the temperature of wave soldering needs to be controlled at about 260 degrees, and the temperature of reflow soldering is about 260-270 degrees.
6. The melting point of lead free HASL is about 183 degrees, the temperature of the tin stove needs to be controlled at 245-260 degrees, the temperature of wave soldering needs to be controlled at about 250 degrees, and the temperature of reflow soldering is about 245-255 degrees.
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Choosing the surface finish is an essential step in the design of your printed circuit boards.
The PCB surface finish helps protect copper circuitry from corrosion. It also provides a solderable surface for your components. There are a number of factors to consider, including:
Below are 5 types of PCB surface finishes, along with their benefits and drawbacks.
&#;Hot Air Solder Leveling&#; is the least expensive type of PCB surface finish.
It is widely available and very economical. The board is dipped in molten solder and then leveled off with a hot air knife. If you&#;re using through-hole or larger SMT components, HASL can work well. However, if your board will have SMT components smaller than or SOIC, it is not ideal.
The surface is not completely level, so this can cause issues with small components. The solder used is typically Tin-Lead. That means that it isn&#;t RoHS compliant. And if reducing the amount of lead you use is important, you may want to choose Lead-Free HASL instead.
Advantages:
Disadvantages:
Lead-Free HASL is similar to standard HASL, but with an obvious difference&#; It doesn&#;t use Tin-Lead solder.
If you want to learn more, please visit our website multilayer pcb design tips.
Instead, Tin-Copper, Tin-Nickel or Tin-Copper-Nickel Germanium may be used. This makes Lead-Free HASL an economical and RoHS compliant choice. But like standard HASL it is not ideal for smaller components.
For boards with smaller components, immersion coatings can be a better choice. They are slightly more expensive but more suitable for this purpose.
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Disadvantages:
With all immersion coatings, a chemical process is used.
A flat layer of metal is deposited on the copper traces. The flatness of the coating makes it ideal for small components. Tin is the least expensive type of immersion coating. Although it is an economical choice, it comes with some drawbacks.
The main drawback is that after the tin is deposited onto the copper it begins to tarnish. That means that if you want to avoid lower quality solder joints, you need to do your soldering within 30 days.
If you are expecting a high volume of production this may not be an issue. And if you are using large batches of boards quickly, you can avoid tarnishing. However, if your production volume isn&#;t high, it may be better to choose a coating like immersion silver.
Advantages:
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Immersion silver does not react with copper the way that tin does. However, it does tarnish when exposed to air.
That means it needs to be stored in anti-tarnish packaging.
When stored in proper packaging it will still be solderable for 6-12 months. But once the PCB is removed from its packaging, it will need to go through solder reflow within a day. A higher shelf life can be achieved with gold plating.
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Electro gold flash plating consists of a thin layer of gold over electroless or electrolytic nickel.
This type of plating is hard and durable. It also has a long shelf life, lasting for years. However, its durability and shelf life make it more expensive than any of the finishes mentioned above.
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Remember that when choosing the finish for your PCBs, you need to consider component types and production volume. You&#;ll also need to consider requirements for durability, environmental impact, and cost. By taking all these factors into consideration, you can be sure to make the right choice.
For more information, please visit pcb surface finish comparison.
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