HASL and ENIG are both frequent types of surface finish for PCB. Together with immersion tin, immersion silver, OSP, and other methods, they help to increase the longevity of circuit boards and their high performance.
Let’s focus on HASL and ENIG as the widespread methods you most likely will have to deal with in PCB manufacturing. You’ll review the technicalities, advantages, and disadvantages of both processes.
Hot Air Solder Leveling (HASL) is the most affordable type of surface finish. It is a well-established and solid option featured by nearly every manufacturer.
Hot Air Solder Leveling is the process of coating PCB with molten solder. Then, the excess solder is leveled, or just cut off, with hot air knives — blows of hot air across the copper surfaces.
HASL process is involved with tin, which is not a RoHS-compliant material. Yet, a lead-free version of Hot Air Solder Leveling is also available.
Hot Air Solder Leveling has the following strengths, you may exploit to your benefit:
HASL offers a good cost-to-value ratio. It’s the reason why PCB manufacturer love to use it in low to moderate-cost electronics manufacturing.
Hot Air Solder Leveling also comes with some limitations that you should kindly consider:
If you use Fine-Pitch technology or aim at getting the most reliable components with a low rejection rate, you probably should consider other options.
If you click with hand-soldering well, HASL must be your first choice. It offers the ease of forming solder joints. Adhesion of solder alloy and HASL’s alloy is also good enough since it’s formed on a molecular level. In some cases, HASL is perfect for high-reliability applications.
HASL also will be your primary choice for the production of budget-friendly electronics of various types.
Electroless Nickel Immersion Gold (ENIG) is another fairly common type of surface finish. It requires the usage of expensive consumables, so it’s utilized in the production of high-end PCBs.
The surface plating applied onto copper pads is done through a chemical process. In it, a nickel layer covers the copper layer, followed by a thin immersion gold layer. It’s done through electrolysis.
In this composition, gold prevents copper from rusting. The nickel layer can help to nihilate the diffusion between gold and copper. Besides, nickel also adds to the durability and temperature resistance of the components.
The general process for creating ENIG finish is cleaning, micro-etching, pre-leaching, activation, ENIG plating, and chemical leaching.
ENIG it’s one of the solid copper finishes, presented with the following benefits:
ENIG is ideal for high-cost customer electronics and specialized, industry-level devices and controllers.
ENIG also has some weaknesses to consider before opting for it:
If you are looking for cost-effective solutions, ENIG can hardly be your first choice.
ENIG is frequently used in SMT, lead-free soldering, and BGA packages. Data and telecom, consumer, aerospace, military, and medical industries are among the major consumers of ENIG processed electronics.
Besides, you may use ENIG finish to produce flexible PCBs. These are of high need for fabrications of microelectronics.
In essence, HASL and ENIG are different finish processes that may help you to achieve distinct manufacturing outcomes. HASL is perfectly suitable for low-cost and mass-production PCBs. At the same time, ENIG is intended for specialized purposes and high-end devices.
There are some aspects in which you have to rely on one or another finish only. Examples are the need to use plating through the hole or prevent black pad syndrome. Guide your choice based on your manufacturing goals.
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