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.
For more information, please visit CHANYEE.
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
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
If you want to learn more, please visit our website lead-free hasl.
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.
The surface finishes are important for a printed circuit board because they protect the board from oxidation. Along with making the boards resistant to corrosion, the surface finishes also help enhance the look of the PCBs. Different finishes have their own pros, cons, and uses. Are you intrigued to know these different types of finish options? What are their pros and cons? The following post is focused to answer these two questions. Read on to know more.
Surface Finishes- Their Types, Pros, and Cons
A printed circuit board can be applied with a variety of finishes, depending upon the application requirements. Here are a few most common types of surface finishes, along with the benefits that they offer. Also discussed are their disadvantages.
HASL (Hot Air Solder Leveling) / Lead Free HASL: HASL is one of the most commonly used, and most popular choices of surface finishes for several years. This finish has the capability to solder easily to the other surface. However, it has its own set of advantages and disadvantages, which are as follows:
Pros:
Cons:
Immersion Silver: This is yet another commonly used surface finish, which is preferred by most manufacturers. These finishes are organic, as well as metallic in nature. It consists of OSP (Organic Solderability Preservative), which helps protect it from tarnishing. Here are some advantages of using this type of surface finish:
Pros:
Cons:
Immersion Gold: Commonly known as Electroless Nickel Immersion Gold, or ENIG, this surface finish has two layers of metallic coating. After the implementation of RoHS regulations, these surface finishes shot to popularity. This finish provides low contact resistance to the thin gold deposits. The following are some pros and cons of this finish:
Pros:
Cons:
OSP (Organic Solderability Preservative):This surface finish is most commonly used for copper pads. No toxins are introduced into the process, which makes this surface finish environmentally friendly. The finish provides an organometallic layer, with the help of a water-based organic compound. Just like any other finish type, the OSP also has its own merits, and demerits, which are as follows:
Pros:
Cons:
ENEPIG (Nickel Palladium):ENEPIG stands for Electroless Nickel Electroless Palladium Immersion Gold. Commonly referred as Nickel Palladiuim, this surface finish is now being used increasingly in the printed circuit boards. This type of finish is ideal for aluminum and gold trace binding. The following are some advantages and disadvantages of choosing this as your finish option:
Pros:
Cons:
Immersion Tin:The chemical processes involved in the immersion coatings are generally costly. However, that required for immersion tin surface finish is least expensive of all. A chemical displacement reaction is used to deposit immersion tin on the surface of a printed circuit board. This type of finish is most commonly used for fine pitch products.
Pros:
Cons:
Hard Gold: Hard gold finish, which is also sometimes referred as the hard electrolytic gold finish is commonly used over edge connector fingers and keypads, which are prone to extreme wear. In this finish, nickel, which acts as a barrier coat is plated by adding gold to it. It can be seen most commonly used on the game cartridges.
Pros:
Cons:
All these benefits offered by the finishes make them extremely important in the printed circuit board industry. Thus, a printed circuit board assembly is said to be complete, only after applying the proper surface finish. On the other hand, the cons of these finishes can make one think, whether to go with a particular finish type or not. This totally depends on the requirements of the application. Are you confused about which is the right surface finish for your PCB? Rigiflex is one among such few manufacturers, who can guide you in selecting the right type of surface finish for your PCBs, based on your application requirements.
Are you interested in learning more about multilayer pcb design tips? Contact us today to secure an expert consultation!