Types of PCB Surface Finishes: Does it Matter Which One You Use?

October 16, 2018 , in Blog

When I was a kid, the end of the summer was both a sad time and a happy one. It was sad because it meant that the glorious time of focusing primarily on playing and having fun was about to end. But it was also happy because it meant that I was going to get some new clothes. My criteria for picking out clothes was whether or not I looked cool in them. My mom, on the other hand, was more concerned with how they would protect me from the weather, stand up to the stress I was going to put them through, and of course, how much they cost.

A PCB designer needs to be more like my mom when it comes to deciding what type of PCB surface finish to use. Just as the main function of clothes is to protect you from your environment, PCB surface finishes are intended to protect your board from external harm. Without this protection, your board may fall prey to oxidation or contamination. Although your choices aren’t nearly as extensive as when shopping for clothes, there are several options to choose from. Let’s explore the types of PCB surface finishes and see when we should opt for which type.

PCB with ENIG finish

Types of PCB Surface Finishes

During PCB design, considerable attention is given to the PCB layout and the specification of materials, which may include the substrate, laminate and core for your board’s layer stackup. These selections are common to all good design for manufacturing (DFM) utilization; however, the many options for PCB surface finish are too often not given sufficient consideration. Instead, the software default is used. Yet, the surface finish is a very important consideration that impacts PCB assembly and your board’s reliability by protecting copper traces and strengthening solder connections. Moreover, there are several types of PCB surface finishes, as listed below.

  • Hot Air Solder Level (HASL)
  • Lead-Free HASL
  • Organic Solderability Preservative (OSP)
  • Immersion Silver (Au)
  • Immersion Tin (Sn)
  • Electroless Nickel Immersion Gold (ENIG)
  • Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG)
  • Electrolytic Wire Bondable Gold
  • Electrolytic Hard Gold

Making the right selection for your design requires an understanding of the differences among the available types.

Which Type of PCB Finish Should I Use?

The best way to answer this question is probably to compare the types of PCB surface finishes against a set of well-defined attributes that will most likely affect your decision. A good list of attributes should include the following:

  1. Lead-free solder – Adheres to restrictions of hazardous substances (ROHS) regulations.
  2. Handling sensitivity – Susceptible to contamination or breakage from handling.
  3. Wire bondable – Capable of forming good wire bound connections.
  4. Tight pitch – Can be used for tight pitch components, such as ball grid arrays (BGAs).
  5. Contact usage – Cen the contact be used for contacts.
  6. Shelf life – Has good shelf life, can be stored for six months are more.
  7. Additional cost – Typically adds cost to your PCB manufacturing.

Now, with a set of comparison attributes, we can better approach the question of which type of PCB finish to use.

Comparison of Types of PCB Surface Finishes

ATTRIBUTES
Surface FinishesLead-free

Solder

Handling

Sensitivity

Wire BondableTight PitchContactsShelf

Life

Extra

Cost

HASL
Lead-free

HASL

OSPAl ▨

Immersion

Ag

Al ▨

Immersion

Sn

ENIGAl ▨
ENEPIG

Al ▨

Au ▨

Electrolytic

Wire Bondable

Gold

Al ▨

Au ▨

Electrolytic

Hard

Gold

Al ▨

 

The attributes above are important and can be used to help you choose the best type of PCB surface finish. However, you should consult your contract manufacturer (CM) for specific cost differences and other factors that may influence your decision, like additional turnaround time, for instance.

Tempo‘s Custom PCB Manufacturing Service

  • Accurate quote in less than 1 day.
  • Performs entire turnkey process in as fast as 3 days.
  • Emphasizes DFM to eliminate time-consuming back-and-forth design corrections.
  • Sources components from the most reputable suppliers in the industry to reduce procurement time.
  • Performs multiple automated inspections during assembly to ensure PCB quality for prototyping.
  • Provides support throughout the PCB manufacturing process, beginning with design.
  • Smooth transition from prototyping to production.

Whether your greatest concern is an organic surface finish as opposed to metallic, lead-free solder instead of lead-based, or turnaround time, Tempo Automation can assist you in making the best selection among the many types of surface finishes available for your design. As industry leaders in precise, high quality and fast PCB manufacturing, our primary motivation is to ensure that you have the best experience and achieve your desired results.

And to help you get started on the best path, we furnish information for your DFM and enable you to easily view and download DRC files. If you’re an Altium user, you can simply add these files to your PCB design software.

If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on types of PCB surface finishes or how to select the best option for your design, contact us.

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