网赌ag全部是一个平台的吗

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PCB Surface Finishes

PCB Surface Finishes

A PCB surface finish is crucial for a printed circuit board as it prevents the copper (exposed traces, pads, holes and ground plains) from oxidation – a critical ingredient to high-level application performance.

A surface finish is essential for making a reliable connection between the PCB and the electronic component. A surface finish has two major functions, to provide a solderable surface for sufficient soldering components to the PCB, and to protect any exposed copper from oxidizing.

网赌ag全部是一个平台的吗 When it comes to choosing the right type of final surface finish, it is just as important as selecting the right material for your bare board. Selecting the correct surface finish for your application is critical for performance. For assistance with selecting a surface finish, send our trusted engineers an email or call.

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With increasing demands for thin, high-density, fast speeds, and lightweight applications, the solder finish will make all the difference.

Modern surface finishes are lead-free, in accordance with Restriction of Hazardous Substances (RoHS) and Waste Electrical and Electronic Equipment (WEEE) directives, and include:

网赌ag全部是一个平台的吗 Choosing the correct PCB surface finish for your application requires taking factors into account like cost, the final application environment (e.g. high-heat/thermal, vibration/stability, RF), component density/selection, lead/lead free requirements, shelf life, shock/drop resistance, production volume, and throughput.

Due to the increased demand for improved performance of electronic applications, surface finishes have also been upgrading. Because of tighter PCB topography the HASL surface finish is quickly being replaced by gold-based surface finishes like ENIG, ENEPIG, and soft/hard gold. The gold-based surface finishes have a lot to offer in terms of features and benefits when used in applications.

ENEPIG Comparison Diagram | San Francisco Circuits

网赌ag全部是一个平台的吗 Diagram illustrating the difference between ENIG and other surface finishes

ENIG (Electroless Nickel Immersion Gold)

ENIG PCB Surface Finish | San Francisco Circuits

Example of an ENIG Surface Finish on PCB

 

网赌ag全部是一个平台的吗 ENIG consists of two layers of metallic coating, which are deposited on the copper surface through chemical process, 2-5μ inches of immersion Gold (Au) over 120-240μ inches of electroless Nickel (Ni).

The nickel layer protects the copper from oxidation, and the gold layer protects the nickel layer. This dramatically increases the resistance to corrosion and also maintains a flat surface which is crucial for assembly of leadless components. ENIG usage has become very common now due to the accountability for lead-free regulations.

 

ENIG (Electroless Nickel Immersion Gold)
PROS CONS MOST COMMON USES

Flat Surface - Excellent for Assembly of Dense Topography PCBs

Long Shelf Life

网赌ag全部是一个平台的吗 Great for Plated Holes and Fine Pitch / BGA / Small Components

Wire Bondable (When Aluminum Wire Is Used)

High Temperature Resistance

网赌ag全部是一个平台的吗 Expensive

Significant Signal Loss

Unable to Rework

Black Pad / Black Nickel

Not Suitable for Touch Contact Pads

网赌ag全部是一个平台的吗 High Density PCBs

网赌ag全部是一个平台的吗 Rigid PCBs

Flex PCBs

Industries: Consumer, Data/Telecom, Aerospace, Military, High Performance, and Medical

 

Properties of ENIG

Properties ENIG

Contact Applications

Yes

网赌ag全部是一个平台的吗 Deposit

Immersion

Exposed Copper

No

网赌ag全部是一个平台的吗 Handling

网赌ag全部是一个平台的吗 Normal

网赌ag全部是一个平台的吗 Process Control

Fair

Process Cost

Medium

Required Thermal Cycles

网赌ag全部是一个平台的吗 >2

Shelf Life

Long (1+ Years)

网赌ag全部是一个平台的吗 SMT

网赌ag全部是一个平台的吗 Flat

Thickness

3 - 10 µin of Gold over
150 - 200 µin of Nickel

网赌ag全部是一个平台的吗 Thin Board Finish

Yes

Applications of ENIG

Applications ENIG

网赌ag全部是一个平台的吗 BGA & μBGA

网赌ag全部是一个平台的吗 Yes

Contact/Connector

网赌ag全部是一个平台的吗 Yes

Fine Pitch SMT

Yes

Flip Chip

Yes

High Reliability

High

网赌ag全部是一个平台的吗 RoHS Compliant

Yes

网赌ag全部是一个平台的吗 Solder Joint Integrity

网赌ag全部是一个平台的吗 Good

网赌ag全部是一个平台的吗 Wire Bonding

Yes (Al)

 

ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold)

ENEPIG is probably not new to you, but it is a surface finish that has become increasingly popular recently due to the price reductions in palladium. It also has increased in popularity and use because of its many features and benefits. It also has a distinct advantage over the ENIG surface finish, which we’ll get into below.

网赌ag全部是一个平台的吗 The ENEPIG surface finish is composed of four metal layers:

  • Copper
  • Nickel
  • Palladium
  • Gold

 

ENEPIG Comparison Diagram | San Francisco Circuits

网赌ag全部是一个平台的吗 Diagram illustrating the difference between ENEPIG and other surface finishes.

 

The difference between ENEPIG and ENIG is the added layer of palladium. The palladium helps protect the nickel layer from corrosion, which helps prevent “black pad” from occurring. This is one of the distinct advantages of ENEPIG over the ENIG surface finish. The immersion gold layer that sits atop the palladium offers nearly-complete board protection by protecting and preserving the palladium underneath.

网赌ag全部是一个平台的吗 When compared to other surface finishes, like hard gold and soft gold plating, ENEPIG has become more affordable in recent years. The cost of the ENEPIG surface finish decreased because the added palladium layer reduces the required thickness of the more expensive gold layer.

ENEPIG is Capable of Your Demanding Requirements

网赌ag全部是一个平台的吗 The ENEPIG finish is capable of the majority of the ultra-demanding requirements with multiple package types like, through-holes, SMT, BGA, wire bonding, and even press fit.

 

ENEPIG PCB Example | San Francisco Circuits

网赌ag全部是一个平台的吗 The ENEPIG surface finish is capable of ultra-demanding requirements.

 

The PCB surface finish with ENEPIG is very thin (between 0.05μm and 0.1μm), making the assembly and soldering process very simple and definitely more reliable when compared to ENIG. ENEPIG also has a long shelf life due to its durability and resistance from tarnishing.

 

ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold)
PROS CONS MOST COMMON USES

Black Pad Free

网赌ag全部是一个平台的吗 Good for Touch Contact / Push Contact

网赌ag全部是一个平台的吗 Higher Reliability Wire Bonding than ENIG

网赌ag全部是一个平台的吗 Stronger Solder Reliability than ENIG

Cheaper than Electrolytic Gold

Lead Free & RoHS Compliant

Long Shelf Life

Multiple Reflow Soldering Capability

Flat Surface - Excellent for Solderability

Great for Plated Holes and Fine Pitch / BGA / Small Components

Easier Inspections

网赌ag全部是一个平台的吗 More Expensive than ENIG

网赌ag全部是一个平台的吗 May Not Be As Reliable for Gold Wire Bonding When Compared to Soft Gold

网赌ag全部是一个平台的吗 Multi-Layer PCBs

High Density Assemblies

网赌ag全部是一个平台的吗 Mixed Package Technologies

网赌ag全部是一个平台的吗 Industries: Military, Medical, Aerospace, High Performance Devices

 

Properties of ENIG

Properties ENEPIG

网赌ag全部是一个平台的吗 Contact Applications

Yes

网赌ag全部是一个平台的吗 Deposit

网赌ag全部是一个平台的吗 Immersion

Exposed Copper

网赌ag全部是一个平台的吗 No

Handling

Normal

Process Control

网赌ag全部是一个平台的吗 Fair

网赌ag全部是一个平台的吗 Process Cost

High

网赌ag全部是一个平台的吗 Required Thermal Cycles

网赌ag全部是一个平台的吗 >2

网赌ag全部是一个平台的吗 Shelf Life

Long (1+ Years)

SMT

Flat

Thickness

1 - 2 µin of Gold over 4 -
8 µin or 8 - 15 µin Palladium
网赌ag全部是一个平台的吗 over 100 -150 µin Nickel

Thin Board Finish

Yes

Applications of ENEPIG

Applications ENEPIG

网赌ag全部是一个平台的吗 BGA & μBGA

Yes

网赌ag全部是一个平台的吗 Contact/Connector

Yes

Fine Pitch SMT

Yes

Flip Chip

Yes

High Reliability

High

网赌ag全部是一个平台的吗 RoHS Compliant

网赌ag全部是一个平台的吗 Yes

Solder Joint Integrity

Good

网赌ag全部是一个平台的吗 Wire Bonding

网赌ag全部是一个平台的吗 Yes

 

Electrolytic Nickel/Gold - Ni/Au (Hard/Soft Gold)

网赌ag全部是一个平台的吗 Depending on applications, printed circuit board technologies use gold extensively. Gold has good electrical conductivity, tarnish resistance, solderability after storage, and being excellent etch resist.

Electrolytic Ni/Au has a layer of gold plating over a base of electroplated nickel. The purity of the gold plating categorizes this finish as either hard gold (99.6% purity) or soft gold (99.9% purity). The choice of hard gold versus soft gold depends on the type of application you are looking to create

Hard Gold & Soft Gold Surface Finish PCB | San Francisco CircuitsHard Gold & Soft Gold Surface Finish PCB | San Francisco Circuits

网赌ag全部是一个平台的吗 Examples of the Hard/Soft Gold Surface Finish

 

Hard Gold Surface Finish

Hard gold is a gold alloy with complexes of cobalt, nickel or iron. A low-stress nickel is used between gold over-plating and copper. Hard gold is not suitable for wire bonding.

We recommend using the hard gold surface finish for components and applications with heavy usage and a high likelihood of wear and tear, like:

The thickness of the hard gold surface finish will vary depending on the applications. When hard gold is used for compliance in military applications, the minimum thickness shall be 50 -100 micro inch. 

Nonmilitary applications require 25 to 50 micro inches. Here are the recommended minimum and maximum thickness values:

  • 17.8 μin is recommended for IPC maximum solderable thickness
  • 25 μin gold over 100 μin nickel for IPC Class 1 & Class 2 applications
  • 50 μin gold over 100 μin nickel for IPC Class 3 applications

 

Properties of Hard Gold

Properties Hard Gold

网赌ag全部是一个平台的吗 Contact Applications

Yes

网赌ag全部是一个平台的吗 Deposit

Electrolytic

Exposed Copper

网赌ag全部是一个平台的吗 Yes

Handling

Normal

Process Control

网赌ag全部是一个平台的吗 Fair

Process Cost

网赌ag全部是一个平台的吗 High

Required Thermal Cycles

>2

网赌ag全部是一个平台的吗 Shelf Life

网赌ag全部是一个平台的吗 Long (1+ Years)

SMT

网赌ag全部是一个平台的吗 Flat

Thickness

98% Pure, 23 Karat 30 -
50 µin over 100 - 150 µin
of Nickel

Thin Board Finish

网赌ag全部是一个平台的吗 Yes

Applications of Hard Gold

Applications Hard Gold

BGA & μBGA

Yes

Contact/Connector

Yes

Fine Pitch SMT

网赌ag全部是一个平台的吗 Yes

Flip Chip

Yes

网赌ag全部是一个平台的吗 High Reliability

Medium/High

RoHS Compliant

Yes

网赌ag全部是一个平台的吗 Solder Joint Integrity

Poor

Wire Bonding

No

 

Soft Gold Surface Finish

A soft gold finish, as the name suggests, contains a higher gold purity on the outer gold plating. Soft gold has a 99.9% purity.

 

Soft Gold Surface Finish PCB | San Francisco Circuits

An example of the soft gold surface finish on a PCB

 

Soft gold finish is used for boards designed mostly for applications that require wire bonding, high solderability and weldability. Soft gold produces a much stronger welded joint when compared to hard gold.

 

Hard Gold & Soft Gold Surface Finish PCB Diagram | San Francisco Circuits

Electrolytic Ni/Au has a layer of gold plating of varying thickness

 

Generally speaking, and with all other factors being equal, Electrolytic Nickel/Gold is the most expensive PCB surface finish. However, some applications do require the Electrolytic Nickel/Gold surface finish.

 

Properties of Soft Gold

Properties Soft Gold

Contact Applications

Yes

Deposit

Electrolytic

网赌ag全部是一个平台的吗 Exposed Copper

网赌ag全部是一个平台的吗 No

网赌ag全部是一个平台的吗 Handling

Normal

Process Control

网赌ag全部是一个平台的吗 Fair

Process Cost

High

Required Thermal Cycles

>2

Shelf Life

Long (1+ Years)

SMT

Flat

Thickness

99.99% Pure, 24 Karat 30
- 50 µin over 100 - 200 µin
of Nickel

Thin Board Finish

网赌ag全部是一个平台的吗 Yes

Applications of Soft Gold

Applications Soft Gold

BGA & μBGA

Yes

Contact/Connector

No

网赌ag全部是一个平台的吗 Fine Pitch SMT

Yes

Flip Chip

网赌ag全部是一个平台的吗 Yes

High Reliability

High

RoHS Compliant

Yes

网赌ag全部是一个平台的吗 Solder Joint Integrity

网赌ag全部是一个平台的吗 Poor

Wire Bonding

网赌ag全部是一个平台的吗 Yes (Au)

 

Immersion Silver Surface Finish

Immersion Silver (also called immersion Ag) is a RoHS compliant (lead-free) surface finish that is an ideal choice for flat surface requirements and fine pitch components with reasonable costs. This surface finish can also replace Immersion Gold over Electroless Nickel (Au/Ni) for most applications. And the thickness ranges from 0.12 to 0.40 μm.

网赌ag全部是一个平台的吗 It has a decent shelf life of 6 to 12 months, but it can be sensitive to contaminants found in the air and on some surfaces. This makes it critical to have a highly qualified boardhouse to properly control and expedite the board packaging process. This surface finish is also subject to tarnishing, which is something to take into account.

As mentioned above, common applications include flat surface requirements, which may include:

  • Membrane Switches
  • EMI Shielding
  • Aluminum Wire Bonding
  • Very Fine Traces

 

Immersion Silver
PROS CONS MOST COMMON USES

RoHS Compliant

Planar

Great for Fine Pitch / BGA

Cost Effective

网赌ag全部是一个平台的吗 Highly Stable

网赌ag全部是一个平台的吗 Simple Processing

网赌ag全部是一个平台的吗 Very Flat Surface

网赌ag全部是一个平台的吗 Reworkable

网赌ag全部是一个平台的吗 Excellent Solderability

Subject to Tarnishing

网赌ag全部是一个平台的吗 Silver Metal Whiskering

网赌ag全部是一个平台的吗 High Friction Coefficient

网赌ag全部是一个平台的吗 Sensitive to Contaminants

Strict Storage and Handling Requirements

Welding Issues with Micro-Holes

Prone to Electromigration

网赌ag全部是一个平台的吗 Difficulty with Electric Testing

 

 

Properties of Silver

Characteristics Silver

Contact Applications

网赌ag全部是一个平台的吗 No

Deposit

网赌ag全部是一个平台的吗 Immersion

Exposed Copper

网赌ag全部是一个平台的吗 No

Handling

网赌ag全部是一个平台的吗 Critical

Process Control

网赌ag全部是一个平台的吗 Fair

Process Cost

网赌ag全部是一个平台的吗 Medium

网赌ag全部是一个平台的吗 Required Thermal Cycles

>2

网赌ag全部是一个平台的吗 Shelf Life

Medium (9-12 Months)*

SMT

Flat

Thickness

6 - 18 µin

Thin Board Finish

Yes

*Requires Unique Storage Techniques µin = Microinches

Applications of Silver

Applications Silver

BGA & μBGA

网赌ag全部是一个平台的吗 Yes

Contact/Connector

No

Fine Pitch SMT

Yes

Flip Chip

Yes

High Reliability

网赌ag全部是一个平台的吗 Medium/High

网赌ag全部是一个平台的吗 RoHS Compliant

Yes

网赌ag全部是一个平台的吗 Solder Joint Integrity

网赌ag全部是一个平台的吗 Excellent

网赌ag全部是一个平台的吗 Wire Bonding

网赌ag全部是一个平台的吗 No

 

Immersion Tin (Also known as White Tin)(ISn)

What is Immersion Tin?

Immersion Tin is a is a RoHS compliant (lead-free) surface finish that is an ideal choice for flat surface requirements and fine pitch components. White Tin (Immersion Tin) is a deposit of a thin layer of Tin on Copper layer of a PCBs. It is not used as often as other surface finishes because not all PCB manufacturers网赌ag全部是一个平台的吗 offer it. The flatness of this particular coating makes this an ideal surface finish choice for small geometries and components.

网赌ag全部是一个平台的吗 Tin also is the least expensive type of immersion coatings. Although it is an economical choice, it does come with some drawbacks.

It’s Not Without Its Drawbacks

Immersion Tin has its advantages, but there are a few disadvantages to using this surface finish. As you may know, Copper and Tin have a strong affinity for one another. This means, over time, diffusion of one metal into the other will occur. It directly impacts the shelf life of the Immersion Tin deposit and ultimately the performance of the ?nish.

Immersion Tin has a limited shelf life, 3-6 months. For the best results assembly (soldering) shall happen during 30 days.

网赌ag全部是一个平台的吗 Tin Whiskering is also another downside to using Immersion Tin as a surface finish. The negative effects of tin whiskers growth are well described in industry related literature and topics of several published papers.

网赌ag全部是一个平台的吗 The Immersion Tin finish is not very durable, therefore, PCBs with Immersion Tin finish must be handled with caution.It provides a consistently flat surface approximately 20-40 micro inches in thickness.

Why Is It Used?

Immersion Tin has been primarily used as an alternative to a lead-based surface finish. It is also used for its very flat and smooth finish making it ideal for fine geometries and fine pitch surface mount components.

Another reason to use immersion tin is sustainability. Elements that may be difficult to source on a consistent basis are used in other finishes, such as ENIG or HASL. Additionally, it uses less water and chemicals in the application process.

It is also easier to re-work.

As with all of the surface finishes we’ve compared so far, there are a number of advantages and disadvantages. Here are the advantages and disadvantages for Immersion Tin.

Advantages:

  • Immersion Tin Finish allows excellent flatness (suitable for SMT), good for fine pitch / BGA / smaller components
  • Immersion Tin has mid-range cost for lead-free finish
  • Press fit suitable finish
  • Retains good solderability after multiple thermal excursions
  • Suitable for horizontal production line.
  • Suitable for fine geometry processing, lead-free assembly.

Disadvantages:

  • Sensitive to handling.
  • Short shelf life, tin whiskering can occur after 6 months
  • Aggressive to solder masks
  • Not recommended to use with peelable masks
  • Not a suitable choice for a contact switches.
  • Special setting requires (soft probe landing) for electrical test

网赌ag全部是一个平台的吗 Here is a full table with some of the pros and cons along with some of the most common uses for the Immersion Tin surface finish.

 

Immersion Tin
PROS CONS MOST COMMON USES

RoHS Compliant

网赌ag全部是一个平台的吗 Great for Fine Pitch / BGA

Cost Effective

网赌ag全部是一个平台的吗 Highly Stable

网赌ag全部是一个平台的吗 Simple Processing

Very Flat Surface

网赌ag全部是一个平台的吗 Reworkable

Excellent Solderability

Subject to Tarnishing

Silver Metal Whiskering

网赌ag全部是一个平台的吗 High Friction Coefficient

Sensitive to Contaminants

Strict Storage and Handling Requirements

Difficulty with Electric Testing

 

 

Properties of White Tin

Properties White Tin

网赌ag全部是一个平台的吗 Contact Applications

网赌ag全部是一个平台的吗 No

网赌ag全部是一个平台的吗 Deposit

Immersion

Exposed Copper

No

Handling

网赌ag全部是一个平台的吗 Normal

Process Control

Fair

Process Cost

Medium

Required Thermal Cycles

>2

网赌ag全部是一个平台的吗 Shelf Life

Medium (9-12 Months)*

网赌ag全部是一个平台的吗 SMT

Flat

Thickness

25 - 60 µin

Thin Board Finish

Yes

*Requires Unique Storage Techniques µin = Microinches

Applications of White Tin

Applications White Tin

网赌ag全部是一个平台的吗 BGA & μBGA

网赌ag全部是一个平台的吗 Yes

网赌ag全部是一个平台的吗 Contact/Connector

No

Fine Pitch SMT

Yes

网赌ag全部是一个平台的吗 Flip Chip

Yes

网赌ag全部是一个平台的吗 High Reliability

网赌ag全部是一个平台的吗 Medium

网赌ag全部是一个平台的吗 RoHS Compliant

Yes

Solder Joint Integrity

网赌ag全部是一个平台的吗 Good

网赌ag全部是一个平台的吗 Wire Bonding

No

 

HASL & Lead Free HASL (Hot Air Solder Leveling) / Sn/Pb

网赌ag全部是一个平台的吗 Hot Air Solder Leveling (HASL) is one of the most commonly used surface finishes in the industry. HASL is divided into two types, and there are two types because one contains tin with lead and the other contains tin without lead. HASL is also one of the least expensive types of PCB surface finishes available. This means access to this surface finish is widely available and it's also very economical.

The HASL Surface Finish Process

网赌ag全部是一个平台的吗 To create a HASL surface finish, a board is submerged in molten solder (tin / lead). The solder then covers all of the exposed copper surfaces on the board. Upon leaving the molten solder, high pressure hot air is blown over the surface through air knives, this levels the solder deposit and removes the excess solder from the board surface.

网赌ag全部是一个平台的吗 HASL provides a very reliable solder joint and shelf life. HASL makes component soldering very effective, but due to the thickness of HASL coating, the planarity of the surface may be unsuitable for fine-pitch components. The HASL deposit is made from a eutectic blend of tin and lead.

网赌ag全部是一个平台的吗 If you're using through-hole or larger SMT components, HASL can work well. However, if your board will have SMT components smaller than 0805 or SOIC, it is not ideal.

One of the unintended benefits of the HASL process is that it will expose the PCB to temperatures up to 265°C which will identify any potential delamination issues well before any expensive components are attached to the board.

There are some distinct advantages and disadvantages with the HASL surface finish.

Advantages:

  • Low Cost
  • Widely Available
  • Re-workable
  • Excellent Shelf Life
  • Excellent solderability
  • Inexpensive / Low cost
  • Allows large processing window
  • Long industry experience / well-known finish
  • Longer storage time
  • When PCB is completed, the pads are completely covered with tin before welding
  • Suitable for lead-free soldering
  • Mature Surface Finish Choice
  • Can be in visual inspection and electrical measurement

Disadvantages:

  • Uneven Surfaces
  • Not Good for Fine Pitch
  • Contains Lead (HASL)
  • Thermal Shock
  • Solder Bridging
  • Plugged or Reduced PTH's (Plated Through Holes)
  • Difference in thickness/topography between large and small pads
  • Not suited for < 20mil pitch SMD & BGA
  • Not ideal for HDI products
  • Not suitable for line binding; due to surface roughness problems, there are limitations in the SMT; Can not be used touch switch.
  • If the board is subjected to high temperatures, the copper will dissolve
  • Particularly for thick or thin panel, HASL is limited, the production processing is not convenient.

The Downsides to Using HASL

For decades HASL was the go-to choice for surface finishes. However, recently, manufacturers have realized it does have limitations. While HASL may be low-cost, the rise of improved surface mount technologies have exposed some shortcomings. One of the downsides of HASL is that it leaves uneven surfaces and is not suitable for fine pitch components. Another downside is that HASL is not lead-free unless requested and having a different process in place. There are other lead-free options that likely makes more sense for a high-reliability product. If a lead-free surface finish is required you may want to try to use Lead-Free HASL.

The HASL surface surface is also not completely level, which can cause issues when used with smaller components. Since the solder is typically Tin/Lead, that means this surface finish is not RoHS compliant. In fact, due to anti-lead laws in the EU, China, California, and many other locations, demands for other lead-free finishes like ENIG, ENEPIG, and other immersion finishes instead of ENEPIG have become better options.

网赌ag全部是一个平台的吗 Unfortunately, HASL is also not very environmentally-friendly. Compared to ENIG, HASL is not a good environmental choice. ENIG is a better choice because it reduces the use of lead and emission from flux and fusing oil in the manufacturing process. And in terms of cost, it might appear at first that HASL is a cheaper option than other options like ENIG. And in most cases HASL is cheaper when being used for a smaller number of boards. But once you start going through two or more boards the cost of HASL is comparable to others like ENIG. And with the other benefits that ENIG offers there's not much reason to choose HASL as your surface finish.

Here is a helpful table to give you a better visual representation of some of the pros and cons of HASL.

 

HASL & Lead Free HASL (Hot Air Solder Leveling) / Sn/Pb
PROS CONS MOST COMMON USES

Low-cost

网赌ag全部是一个平台的吗 Available

Repairable

Uneven Surfaces

网赌ag全部是一个平台的吗 Not good for fine pitch components

Thermal Shock

Not good for plated through-hole (PTH)

Poor wetting

网赌ag全部是一个平台的吗 Mil-spec

网赌ag全部是一个平台的吗 Hobbyist

 

As seen above, HASL can still be a good option for a surface finish, but improvements in other surface finishes are making it obsolete. HASL does have a few benefits, but compared to others like ENIG, ENEPIG, and other immersion finishes, it is falling short. For example, ENIG is corrosion resistant, good for aluminum wire bonding, excellent for fine-pitch technology, excellent solder-ability, has a great shelf-life, and so much more. The features and benefits that made HASL a great choice in the past just cannot compare to the improvements of the other surface finishes.

 

OSP (Organic Solderability Preservatives)

OSP is a different kind of surface finish than we have seen so far. OSP is specifically designed to produce the thin, protective, and uniform layer on the copper surface of PCB’s. This coating actually protects the circuitry from oxidation during storage and assembly. It is applied over copper pads to protect the pad before soldering. This finish actually preserves the copper surface from oxidation by providing an organometallic layer protecting the copper prior to the soldering process. It is also a water-based organic surface finish, which means this surface finish is environmentally friendly. Compared to other surface finishes that have high levels of toxicity or consume large amounts of energy, this surface finish is relatively safe and “green” for the environment.

This surface finish is increasing in popularity due to an increased interest in lead-free techniques and fine pitch solutions.

网赌ag全部是一个平台的吗 It also requires low equipment maintenance.

The Manufacturing Process

The Manufacturing Process | San Francisco Circuits
 

网赌ag全部是一个平台的吗 The manufacturing process for OSP is straightforward as seen in the image above. “Clean” is the starting point with cleaning off organic contaminants such as oil or fingerprints, to not get the copper foil surface contaminated before application. For the best results and performance, the cleaning process should be checked as often as possible. If it does not maintain the standards for cleanliness the performance of the application will be negatively affected.

For Topography enhancement, micro etching is applied to eliminate the oxidation generated on top of the copper foil. This is necessary for the bonding forces to be improved between the copper foil and the OSP solution. Speed is also a very important factor. In order to obtain a smooth and even film, the stability of the micro etching speed needs to be at a level of 1.0?m to 1.5?m per minute.

网赌ag全部是一个平台的吗 In the DI rinse stage after the OSP application, preservatives need to be added in order to protect the OSP solution from being polluted by other ions. If the OSP solution is polluted, tarnishing will occur soon after the reflow soldering stage. It is best that DI rinse should be utilized with preservatives that have a PH value between 4.0 and 7.0.

Handling & Controls

网赌ag全部是一个平台的吗 This surface finish is very simple and easy to control. It also has an advantage over traditional HASL with regards to coplanarity, and its solderability. However, this finish does require significant changes with the type of flux and number of heat cycles used during assembly process.

网赌ag全部是一个平台的吗 Regarding handling of this particular surface finish, there are some definite differences. You cannot touch it with your hands unprotected. Acidic fingerprints will degrade the OSP and leave the copper susceptible to oxidation. Most assemblers prefer to work with metal finishes that are more flexible and endure more heat cycles

网赌ag全部是一个平台的吗 We compiled a list of some of the advantages and disadvantages of the OSP surface finish below:

Advantages:

  • Flat Surface
  • Simple Process, Very Smooth Surface, Lead-Free Soldering and SMT
  • Re-workable, Suitable for a Horizontal Production Line
  • Cost Effective
  • Environmentally Friendly

Disadvantages:

  • Thickness cannot be measured
  • Not Good for PTH (Plated Through Holes)
  • Short Shelf Life
  • Can Cause ICT Issues
  • Exposed Cu on Final Assembly
  • Sensitive Handling
  • Cannot be Welded (reworked) more than twice
  • Not Suitable for Crimping Technology & Line Binding
  • Not Convenient for Visual Inspection and Electrical Measurement
  • Requires Nitrogen Oxide Infused SMT

 

OSP (Organic Solderability Preservatives)
PROS CONS MOST COMMON USES

Lead-Free

网赌ag全部是一个平台的吗 Flat Surface

Simple Process

网赌ag全部是一个平台的吗 Repairable

网赌ag全部是一个平台的吗 Excellent Coplanarity

网赌ag全部是一个平台的吗 Improved Solderability

No 'Black Pad' Issues

Low Cost

网赌ag全部是一个平台的吗 Can Be Wire Bonded

Not Good for PTH

网赌ag全部是一个平台的吗 Sensitive Handling

网赌ag全部是一个平台的吗 Short Shelf life

Big Changes to Assembly Process

网赌ag全部是一个平台的吗 ICT Fixture Probes Can Potentially Damage the PCB

Copper Pad Applications

 

Properties of OSP

Properties OSP

Contact Applications

网赌ag全部是一个平台的吗 No

Deposit

Dipped

网赌ag全部是一个平台的吗 Exposed Copper

Yes

网赌ag全部是一个平台的吗 Handling

Critical

Process Control

网赌ag全部是一个平台的吗 Fair

Process Cost

Poor/Fair

网赌ag全部是一个平台的吗 Required Thermal Cycles

网赌ag全部是一个平台的吗 ~2

Shelf Life

网赌ag全部是一个平台的吗 Medium (9-12 Months)*

SMT

网赌ag全部是一个平台的吗 Flat

Thickness

网赌ag全部是一个平台的吗 8 - 24 µin

网赌ag全部是一个平台的吗 Thin Board Finish

Yes

*Requires Unique Storage Techniques µin = Microinches

Applications of OSP

Applications OSP

网赌ag全部是一个平台的吗 BGA & ?BGA

网赌ag全部是一个平台的吗 Yes

Contact/Connector

No

网赌ag全部是一个平台的吗 Fine Pitch SMT

Yes

Flip Chip

Yes

High Reliability

Medium/High

RoHS Compliant

网赌ag全部是一个平台的吗 Yes

网赌ag全部是一个平台的吗 Solder Joint Integrity

网赌ag全部是一个平台的吗 Good

Wire Bonding

网赌ag全部是一个平台的吗 No

 

网赌ag全部是一个平台的吗 OSP (Organic Solderability Preservatives) is the go-to surface finish for copper pad applications. It is a very specific surface finish and as you can see has several cons associated with it. But for the most part, OSP is a great choice for an organic solution for your surface finish.

 

Connect With us to Discuss Your PCB Surface Finish Needs

网赌ag全部是一个平台的吗 If you are looking for the right surface finish for your PCB assembly, we would love to have a conversation with you. San Francisco Circuits is your partner for all your PCB needs. We are flexible and dependable for your most complicated requests and needs!

We are experts in PCB surface finishes. Call us for help in choosing the right surface finish for your PCB assembly process: 800.SFC.5143 or chat with one of our expert staff members.

Call us: 1-800-SFC-5143

Or EMAIL US网赌ag全部是一个平台的吗 to discuss & quote your project

 

 

San Francisco Circuits Offers the Following Lead-Free PCB Surface Finishes

These are the lead-free PCB surface finishes we have available for your PCB order.
For more information, please contact our experts at 1.800.SFC.5143 or get a PCB production quote.

Gold Finish

网赌ag全部是一个平台的吗 May be Electrolytic Electroless, or Immersion

- ENIG
(Electroless Nickel Immersion Gold)

2-5 micro inches. Purpose: To prevent oxidation, extend shelf life, provide a wire bonding surface (when aluminum wire is used), and used to provide an electrically conductive surface on PCBs. Used for solderability when the flatness of the pad is critical. ENIG has shelf life longer then 12 months.

网赌ag全部是一个平台的吗 - Hard Gold

网赌ag全部是一个平台的吗 Purpose: “Wear and tear” used for Gold Fingers (minimum 30 micro inches),contacts, keypads soldering (maximum 17 micro inches), to prevent oxidation and extend shelf life.

网赌ag全部是一个平台的吗 - Soft Gold

网赌ag全部是一个平台的吗 Purpose: Used for wire bonding (Ultrasonic minimum 2 micro inches/Thermasonic minimum 30 micro inches) and to prevent oxidation and extend shelf life.

Immersion Silver

网赌ag全部是一个平台的吗 Use for solderability purposes (2-10 micro inches). Used for solderability when the flatness of the pad is critical.

网赌ag全部是一个平台的吗 Lead Free Solder

网赌ag全部是一个平台的吗 Use for solderability purposes (70-200 micro inches). Used for solderability when the flatness of the pad is not critical.

OSP
Organic Solderability Preservatives)

网赌ag全部是一个平台的吗 Used for solderability when the flatness of the pad is critical.

网赌ag全部是一个平台的吗 White Tin (Immersion Tin)

网赌ag全部是一个平台的吗 Used for solderability when the flatness of the pad is critical.

 

We Can Help You Choose the Right Surface Finish For Your Applications

网赌ag全部是一个平台的吗 San Francisco Circuits specializes in helping you choose the right PCB surface finish. You have a lot of factors to think about like cost, application environment, lead/lead free requirements, shelf life, and so much more! Let us worry about those things and give you the right PCB surface finish.

When it comes to choosing the right type of surface finish, you want to make sure you select the best one for end performance. That’s where you can work with our trusted engineers who have the experience you need to get what’s best for your situation. We look forward to connecting with you!

 

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