Nelco PCB

This guide covers everything you need to know about Nelco PCB such as applications, glass transition temperature, quality control, and benefits, among other aspects.

It will help you become an expert in Nelco PCB industry – keep reading.

What is Nelco PCB?

This is a printed circuit board constructed using Nelco materials, which give outstanding mechanical and thermal performance.

They are suitable for high speed digital and multilayer PCB applications.

Moreover, all Nelco PCB materials offer high CAF resistance and thermal reliability for compatibility with lead-free assembly and are RoHS compliant.

Which are the Different PCB Surface Finishes in Nelco PCB?

The main types of finishes used in Nelco PCB include:

1) Electroless Nickel Immersion Gold

ENIG is the most common alternative and is utilized on majority of Nelco PCB.

This finish gives a thin, gold solderable film that protects the copper traces using a nickel barrier separating it and the copper.

It is an ideal lead-free alternative that forms a long-lasting finish.

2) Hot Air Solder Leveling

In the case of HASL, the Nelco PCB is clasped vertically using clamps and immersed in a flux bath.

It is then dipped into a melted solder hot vat then the finish, consisting of lead/tin, is flattened out using hot air knives.

Consequently, the PCB is lifted out of the melted solder vat.

This treatment ensures a uniform thickness over the whole board.

HASL finish presently primarily used on aerospace and military applications.

3) Lead-Free HASLI

The features and applications of this finish are similar to HASL, except the alloy contains no lead.

Rather, it can have tin and nickel, tin and copper, or tin, nickel, germanium and copper alloy.

This type of PCB finish is not commonly used.

4) Immersion Tin

In this type of finish, a tin coating is deposited over the copper surface through a chemical process.

It is commonly applied in high-speed Nelco PCBs.

Immersion tin PCB finish works perfectly to protect underneath copper from oxidation.

However, tin and copper in such proximity can cause diffusion from a specific metal to another, leading to issues.

5) Organic Solderability Preservative/Entek

With OSP, a thin coating of material is deposited throughout the copper to screen it before soldering.

This type of PCB organic surface finish is water-based and is not commonly used presently.

6) Hard Gold

Hard gold is applied on top of the nickel, which attaches well and does not disintegrate easily in comparison to other PCB finish types.

Due to its longevity, this type of Nelco PCB finish is employed in applications involving mechanical contact, like keypads and buttons.

7) Immersion Silver

This PCB finish, just as immersion tin, is utilized in high-speed signal applications that do not have any nickel.

However, it does need special storage since it will discolor when exposed to air.

8) Electroless Nickel Electroless Palladium Immersion Gold

ENEPIG is a three-layer metallic finish that is applied in PCBs that as well need wire connection.

The role of the electroless nickel is to shield the copper and to inhibit it from contacting other metals.

Likewise, electroless palladium offers another anti-oxidation coat and prevents the corrosion of nickel.

Finally, the gold layer incorporates more coating against oxidation in addition to covering the PCB completely.

9) Soft Bondable Gold

This type of Nelco PCB has been utilized for years and has similar bonding procedure as ENEPIG.

It has a crowned surface pad implying that there exist minimal space to land wires.

How does NELCO PCB compare to ISOLA PCB?

Isola PCB and Nelco PCB are both high frequency printed circuit boards that offer superior mechanical and thermal performance.

Nonetheless, Nelco PCB uses a myriad of laminate and prepreg materials, while Isola PCB commonly uses copper-clad dielectric prepregs and laminates.

The materials used in the two printed circuit boards are suitable for fabrication of enhanced multilayer PCBs.

Which are the Factors to Consider when Selecting Vias for Multilayer Nelco PCB?

PCB vias are an important component of multi-layer Nelco PCBs, which may prove challenging to design and fabricate.

They provide a path through which thermal and electrical energy can flow across layers.

Therefore, here are the key factors to consider when choosing vias for a multilayer PCB.

· Via Type

You need to determine whether a through, buried or blind via is the appropriate choice for your project.

If you got a single lamination lacking via technology or fill, you will enjoy more space for larger holes.

· Via Size

The most popular via size is 10 mil that would reduce after plating to 7 mil, though via size relies on PCB thickness.

Micro vias, both mechanically drilled and laser drilled 4 mil holes, depends on the Nelco PCB thickness.

· Via Tolerance

It is essential to specify the tolerance of the hole size. Nevertheless, most Nelco PCB fabricators usually give in-house guidelines.

· Right Technology

Consult with your printed circuit board manufacturer to develop a stackup which supports the via technology you need.

· IPC Guidelines

It is important to always comply with IPC instructions for the related technology, which comprise of stipulations like distance between vias.

The design guidelines for military, class 2, class 3, and class 3DS are particularly critical since they all differ moderately.

· Annular Ring

Pay attention on the requirements of the annular ring according to class 2 and 3.

An annular ring is what is formed after drilling through the pads of every layer.

It gives sufficient land area within the interior section to still have a copper linkage to the trace on the specific layer.

It ensures the connection even before doing a through hole plating.

However, there is a lot of tolerance to manage if during vertical drilling.

You will be required to manage the tolerances of materials movement and as well as how the drill drive through the material.

What are the Applications of Nelco PCB?

Designed for lead-free assemblies, high-speed digital applications and multilayer printed circuit boards.

Here are the main uses of Nelco PCB:

• Wireless infrastructure and handsets
• Backplanes
• Automotive
• communications and networking servers

Which are the Key Features of Nelco N4000 Series?

The Nelco N4000-13 series is an advanced epoxy resin system designed to offer both excellent low signal loss/high signal speed and thermal management features.

N4000-13 SI is ideal for applications that need precise impedance regulation and optimum signal integrity.

It also ensures high reliability by thermal and CAF resistance.

Main features of Nelco N4000 series include:

· Compatible with Lead-Free Assembly

The Nelco PCB material is appropriate for assemblies having a maximum reflow temperature of 245 degree Celsius.

However, based on the design and construction processing, the reflow temperature can go up to 260 degree Celsius.

· Robust Thermal Stability

N4000 series has excellent signal loss, thermal and electrical properties.

It is modeled for high-reliability PCBs requiring enhance thermal performance and wide bandwidth.

The series glass transition temperature (Tg) is greater than 210 degree Celsius and has low Z-Axis CTE.

· Low Loss and High Speed

It is suitable for applications falling in the 1-10 GHz frequency range.

Furthermore, the low Dk and Df enables swift signal propagation and low signal distortion for high-performance and high frequency application.

· CAF Resistant

The low Z-CTE and verified CAF resistance offer long-term dependability for both digital and RF applications.

· Signal Integrity Option

If utilized, SI glass gives improved electrical performance even in the most demanding Nelco PCB applications.

· Wide Construction Variety

Nelco N4000 series is available in a broad range of constructions.

The construction span from glass styles to copper weights, comprising of RTFOIL, double treat, and standard copper laminates.

They also exist as a 2 mil system fulfilling the stipulations of a capacitive laminate.

What are the Benefits of a Lower Dielectric constant in Nelco PCB?

The dielectric constant is a measure of the capability of PCB material to get polarized through electric field and accumulate electrostatic energy.

It also refers to the capacity of the material to enable signal propagation, and it varies with frequency.

Materials datasheets commonly denote relative dielectric constant as Dk, with low Dk materials making exceptional insulators.

This makes them ideal for ideal signals isolation on adjacent PCB layers.

Therefore, let’s look at the main advantages of low dielectric constant of Nelco PCB:

• Better insulation
• Faster propagation of signal via the material
• Smaller capacitance of stray trace
• greater trace impedance for a specific trace geometry

How do you Mitigate Material Loss in Nelco PCB?

Impedance mismatches is the main cause of signal loss at lower data rates.

Though minimal, conductor losses and dielectric absorption from the Nelco PCB material also cause signal loss.

Impedance mismatch is well managed by controlling trace routes, separation, and geometries during the PCB layout design.

Nevertheless, at 10 Gbps and beyond data rates, material loss gets very instrumental.

It is important to consider controlled dielectric fabrication during the process of design.

Here are the factors to consider during the material selection process to mitigate loss due to the Nelco PCB material:

• Skin effect
• Loss tangent
• Relative Dielectric Constant
• Fiberglass Weave Composition

These material aspects have considerable effects on the electrical features.

Therefore, you need to consider them as vital aspects during the Nelco PCB stackup design.

Is there Difference between Taconic PCB and Nelco PCB?

The major difference between Taconic PCB and Nelco PCB is the main type of material used in the circuit board.

Taconic PCB mainly use PTFE laminate material.

On the other hand, Nelco PCB apply a variety of materials including high-speed epoxy, FR-4 and High-Tg materials.

It also uses enhanced materials like cyanate ester, BT and polyimide.

However, all these PCB materials are high Frequency laminates that ensure very steady dielectric constant and low dissipation factor.

Is there Difference between Dissipation Factor and Loss Tangent in Nelco PCB Fabrication?

Loss tangent (tan(δ)) is defined as measure of signal loss during signal propagation across the transmission line.

It is commonly referred to as dissipation factor, which is outcome of absorption of electromagnetic wave by the dielectric material.

It is based on the glass-resin composition and structure of the material.

A Lower loss tangent leads to more of the initial conveyed signal reaching its destination.

This is vital for transceiver-based applications in which multi-gigabit signals needs to be conveyed through long backplane channels.

On the other hand, a large loss tangent implies high dielectric absorption and reduced transmitted signal amount reaches its destination.

Basically, choosing Nelco PCB material with the lowest loss is the best option, though lower dissipation factor comes at a raised cost tradeoff.

How does Fiberglass Weave Affect the Performance of Nelco PCB?

The fiberglass inside the core and prepreg is fabricated through weaving glass yarn fibers together to produce fabric-like fiberglass panels.

These panels are then impregnated using an epoxy resin to create core and prepreg materials.

Since the glass yarn has different thicknesses and densities, the final panels can span from tightly-weaved to loosely-weaved fiberglass-epoxy fill.

The weaves are normally grouped into various glass styles, depending on the kind of fiberglass yarn utilized and yarn count.

The more rigid the weave netting, the more steady the dielectric constant of the Nelco PCB.

Loose weaves leading to less steady dielectric constant within the PCB laminate can result in variations in trace impedance.

Moreover, it can cause propagation distortions in closely matched signals, like differential pairs which precisely reference the weave.

What are the Effects of PCB Stackup Design in the Performance of Nelco PCB?

The design of Nelco PCB stackup plays an integral role in the general performance of the system.

This is particularly key in high-performance structures that involve transceiver technology.

It is the substrate on which you assemble all the components of the printed circuit board.

A poor PCB stackupdesign having inappropriately chosen materials can degenerate the electrical capability of signal transmission.

Moreover, it can degrade manufacturability, power delivery, and long term dependability of the final product.

To perfectly design PCB stackup, you should have a great mastery of both PCB fabrication and factors that affect material choice and cost.

A regular Nelco PCB is fabricated from several alternating layers of copper foil, prepreg and core materials heat-pressed and bound together.

How does Glass Transition Temperature Affect Nelco PCB Manufacturability?

Glass transition temperature (Tg) is one aspect that can influence manufacturability of printed circuit board.

All Nelco PCB materials are susceptible to expansion and contraction due to temperature changes.

The expansion and contraction rate is dictated by the coefficient of thermal expansion (CTE) of the material.

Tg is the temperature where the resin in the PCB material starts to expand much rapidly than the surrounding copper and glass weave.

The rapid resin expansion elevates the mechanical pressure on the structure of the PCB.

Since the glass-weave and copper are laminated together, they strengthen the circuit board in the lateral X and Y Axis.

The resulting expansion is compelled happen particularly in the vertical Z Axis.

The fast vertical expansion can over-pressure structures of via leading to via fractures.

It can as well result in PCB delamination in extreme situations when the expansion is too much.

During the selection of Nelco PCB material, choose one having a Tg high enough to sustain the anticipated fabrication temperature cycles.

This should be during both assembly and rework to guarantee PCB fabrication reliability.

For hazardous substances restriction compliant procedures, reflow temperature can withstand 240 degree Celsius or peak at 260 degree Celsius.

What Factors Determine the Number of Layersin Nelco PCB Stackup Design?

The aim of any Nelco PCB stackup design is to choose the material and define the layer ordering.

This should ensure that it sufficiently delivers the needed power integrity and signal performance at the least PCB cost.

The aggregate number of layers needed for a specific design is based on the intricacy of the circuit board.

Therefore, the main factors that determine the number of layers in the stackup design of Nelco PCB include:

• Sum total of signal nets that need to break out from the BGA device
• Sum total of pours or power planes, and
• Component density and packages type for the components.

Normally, independent ground or power plane specifications and large ball grid array breakouts determine the final count of Nelco PCB layer.

How does Copper Weight Influence its use in Nelco PCB?

One-ounce copper is utilized for plane layers and half-ounce copper is usually utilized for signal traces.

Denser copper weights may be utilized for power delivery in case you expect higher DC current.

Nevertheless, thicker copper layers raise the general thickness of board and increase manufacturability concerns associated with drilling and lamination.

Is Hybrid Construction possible with Nelco PCB?

Using hybrid construction is one of the methods of controlling expenses in high speed PCB designs.

In hybrid Nelco PCB construction, only the layer requiring high performance signals utilize a higher cost though lower loss laminate core material.

The remaining layers can employ a lower cost derivative of FR4 core material.

A common hybrid construction requirement is to maintain a uniform prepreg all through the PCB to stick the core layers together.

Blending prepreg in the printed circuit board can lead to lamination problems since varying temperatures may be needed for the proper bonding of the different prepregs.

Why is Board Panelization Important when Sizing Nelco PCB?

Board panelization is key during the initial sizing of Nelco PCB to maximize the quantity of board yield for each PCB panel.

This helps in reducing the cost for each board.

The common dimensions of PCB panel are 12 × 18 inches and 18 × 24 inches.

However, the real usable surface left to the fabricator is usually 1 inch less on all edges of the panel.

Thus, the workable dimensions, are 10 × 16 inches and 16 × 22 inches, respectively.

Furthermore, when panelizing several boards on a printed circuit board panel, the minimal spacing specification between boards should be 100 mils.

This allows the routing out of individual boards after fabrication.

How do you Control Quality of Nelco PCB?

There are different analytical methods for testing the chemical, physical, and/or mechanical characteristics of PCB materials as they are cooled or heated.

Here are the main quality control tests for Nelco PCB:

· Differential Scanning Calorimetry

DSC is among the thermo-analytical techniques employed to access the various chemical and physical characteristics of prepregs and laminates.

It measures variation in heat flow across a resin system in comparison to that via an aluminum reference.

· Thermo-Mechanical Analysis

TMA determines dimensional variation in a PCB material as it heats from room temperature to a set final temperature.

The variation in height, width or length with changing temperature is what is referred to as Coefficient of Thermal Expansion.

· Thermo-Gravimetric Analysis

TGA determines weight loss as a temperature function as a Nelco PCB material is heated.

The heating is either through a regulated heat up ramp or isothermal mode.

· Infrared Spectrophotometry

IR spectrophotometry establishes the “chemical fingerprint” of a PCB material with regard to the characteristic transmission and absorption of infrared frequencies.

What are the Quality Standards for Nelco PCB?

• RoHS standards
• UL standards
• CE standards
• ISO standards
• ASTM standards

Now, before choosing Nelco material for your PCB, ensure the requirements meets the criteria in this guide.

In case you have any questions or you would like to make an inquiry, Venture Electronics is here to help.