Jul. 08, 2024
Choosing the surface finish is an essential step in the design of your printed circuit boards.
The company is the world’s best lead-free hasl supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.
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.
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.
Advantages:
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:
Disadvantages:
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.
Advantages:
Disadvantages:
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.
Advantages:
Disadvantages:
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.
PCB surface finish is a metal or organic coating on PCB pads that protects the copper and boosts solderability. Lead-free HASL (hot air solder leveling) is the most common PCB surface finish, and if you don't specify which surface finish you want, we assume you want lead-free HASL for your boards.
However, lead-free HASL is not allowed for flexible PCBs and rigid PCBs with a thickness smaller than 0.5mm. You have to replace it with ENIG (electroless nickel immersion gold) or OSP (organic solderability preservatives). This article reveals HASL and ENIG and compares them.
HASL means using tin/lead solder to spray the PCB pads and then using hot air to blow the PCB surface so that the pad surface is level. The thickness of HASL is 1mil to 2mil (25.4μm to 50.8μm, or 0.025mm to 0.05mm).
HASL is a cheap PCB surface finish. And its solderability is good.
However, HASL doesn't meet the lead-free requirements in most of the world, and in most cases, we use lead-free HASL.
The properties of lead-free HASL are pure tin. The thickness of lead-free HASL is 0.1mil to 1mil (2.54μm to 25.4μm, or 0.mm to 0.025mm).
Lead-free HASL is the default surface finish from the PCB manufacturer PCBONLINE. Compared with HASL, PCB pads with lead-free HASL look dim, and the soldering temperatures are higher.
HASL
Lead-free HASL
Properties
Tin and lead (37% of lead)
Tin (lead less than 0.5%)
PCB pad finish
Glossy
Dim
Solderability
Good
A little worse than HASL
Are you interested in learning more about multilayer pcb design tips? Contact us today to secure an expert consultation!
Reflow soldering temperatures
210&#; to 245&#;
240&#; to 270&#;
Wave soldering temperatures
About 250&#;
About 260&#;
Though lead-free HASL is common, it can't be applied to rigid PCBs with a thickness smaller than 0.5mm and flexible PCBs, neither HASL. These boards can't bear the spraying force. If you spray tin on these boards, they bend, and only the middle of the boards is sprayed with tin. Sometimes, rigid PCBs with a thickness smaller than 0.5mm may even break if you apply HASL or lead-free HASL to them.
In such cases, you can choose the other PCB surface finish -- ENIG. Or you can also change lead-free HASL to OSP. But OSP is easy to oxide. If you don't solder the PCBs at once, OSP oxides. And the manufacturer has to seal and package the OSP PCBs at once.
ENIG, also known as immersion gold, or chemical Ni/Au, is one of the best PCB surface finishes for almost all PCBs. In any case, if HASL or lead-free HASL can be used, you can replace it with ENIG. But inversely, HASL or lead-free HASL can't replace ENIG.
ENIG means plating a nickel alloy coating on the PCB pads and then a gold coating with chemical reactions. Besides PCB pads, ENIG can also be applied to other areas, such as the PCB edges or wires for thermal dissipation purposes. The thickness of ENIG is 1μm, 2μm, and 3μm. (From the equation 1mil=25.4μm, you can understand how thin the PCB finish ENIG is compared to HASL.)
ENIG PCB pads have a gold color and look shiny. Besides, the solderability of ENIG is the best among all the PCB surface finishes. And because gold has a dense crystal structure and is hard oxide, the protection of ENIG to copper of the PCB pads is also excellent.
ENIG PCBs are high-standard PCBs and they are usually used for high-end applications. As we mentioned above, ENIG can take the place of HASL and lead-free HASL in any case if your budget allows, but HASL and lead-free HASL can't replace ENIG.
Below is a comparison between EENIG and HASL.
ENIG
HASL
Lead-free HASL
Meeting lead-free requirements or not
Yes
No
Yes
Price
High
Low
Middle
Thickness
1μm, 2μm, and 3μm
25.4μm to 50.8μm
2.54μm to 25.4μm
Finish method
Chemical reactions
Spraying
Spraying
Properties
Nickel and gold
Tin and lead
Tin
Applications
Can be used for almost all PCBs
Simple FR4 PCBs with a thickness larger than 0.5mm
Common rigid PCBs with a thickness larger than 0.5mm
PCBONLINE is a one-stop advanced PCB manufacturer founded in , with two large advanced PCB manufacturing bases and one assembly factory. If you have needs for PCB and PCBA fabrication, PCBONLINE can be your reliable PCB/PCBA supplier from prototypes to bulk production.
In PCB surface finishes, PCBONLINE has these advantages:
If you need PCB design, fabrication, assembly, and box build assembly, please feel free to contact PCBONLINE by at .
This article gives an introduction to HASL and ENIG separately and compares them. ENIG is universal for PCBs, especially for high-reliability PCBs. HASL doesn't meet the lead-free requirements but lead-free HASL does. If you don't know whether HASL can be used for your PCB or not, ENIG must be okay. You can also contact PCBONLINE for suggestions.
© This article is an original work of the PCBONLINE team. Please indicate the author PCBONLINE if you reprint. If the article is reproduced without permission or indicating the author's source, PCBONLINE reserves the right to investigate the infringement.
If you want to learn more, please visit our website pcb surface finish comparison.
If you are interested in sending in a Guest Blogger Submission,welcome to write for us!
All Comments ( 0 )