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.
Are you interested in learning more about lead-free hasl? Contact us today to secure an expert consultation!
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 0.0025mm 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
The company is the world’s best multilayer pcb design tips supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.
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 1999, 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 email at info@pcbonline.com.
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.
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?
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.
HOYOGO is an international, professional and reliable PCB Manufacturer. We have a PCB design team with more than 12 years of work experience. The products we produce are rigid PCBs from 2 to 56 layers. At the same time, we can also provide FPC, HDI, and all other special PCB. With our rich experience and technical understanding, as well as our own production capacity and local centralized resources, we can provide you with one-stop service from small, medium to mass production.
If you want to learn more, please visit our website pcb surface finish comparison.