Introduction

Taconic RF-35 is a popular high frequency laminate material designed for performance-driven RF PCB applications. With a dielectric constant of 3.5, low loss, and tight material uniformity, RF-35 enables excellent signal integrity for today’s high speed digital and analog circuits.

This article provides an in-depth look at RF-35 material properties, performance capabilities, design considerations, and applications. We’ll explore everything engineers need to know about specifying and working with this versatile RF material.

RF-35 Overview

Taconic RF-35 is a PTFE composite laminate comprised of:

• Woven fiberglass reinforcement
• Ceramic filler particles
• PTFE (polytetrafluoroethylene) resin system

With a dielectric constant of 3.5, it provides:

• Excellent high frequency signal performance
• Very low loss characteristics
• Tight dielectric constant tolerance

RF-35’s properties make it suitable for a wide range of radio frequency, microwave, millimeter-wave, and multi-gigabit digital applications. It strikes an optimal balance between cost and high frequency signal integrity.

Some key traits of Taconic RF-35 include:

• Dielectric constant of 3.5 +/- 0.05
• Low loss with tight uniformity
• Excellent thermal stability
• Good CTE for reliability
• Lead-free compatible
• US laminator source
• ITAR free
• RoHS compliant
• Cost-effectiveness

For designs from 10+ Gbps digital to Ku band RF, RF-35 delivers proven results across countless commercial and defense programs.

Material Properties

RF-35 is formulated from PTFE reinforced with ceramic particles to achieve:

Dielectric Constant – The k-value determines velocity of signal propagation and affects many circuit parameters. RF-35 provides an Er of 3.5 with very tight +/- 0.05 tolerance for consistent performance. This enables excellent impedance control compared to typical FR-4 (Er=4.5).

Loss Tangent – With a loss tangent of just 0.0019, RF-35 provides very low loss for high frequency energy. This maximizes Q factors in resonant circuits and insertion loss in transmission lines. Wide range of tested Dk from DC to Ku band.

Moisture Absorption – At just 0.02% moisture absorption, RF-35 resists detrimental effects of humidity and water ingress far better than conventional FR-4 material. This enhances long term reliability.

Thermal Performance – With a Z-axis CTE of 82 ppm/C, close PCB/laminate CTE matching reduces stresses under temperature cycling for excellent reliability. Good thermal conductivity (0.71 W/mK) spreads heat.

Lead-Free Assembly – RF-35 achieves high Tg (>280C) allowing compatibility with lead-free solder profiles of up to 260C for modern assembly.

Available Forms

RF-35 laminate allows flexibility through different standard offerings:

Copper Cladding

• 1⁄2, 1, and 2 oz ED copper foil
• Standard HTE copper and rolled copper available
• Double-sided cladding enables signal layers

Core Thicknesses

• From 0.005 inches to 0.125 inches
• Typical stackups use multiple 0.005″ cores
• Thicker cores provide rigidity when needed

Panel Sizes

• 18” x 24”, 18” x 36”, and 24” x 36” standard panels
• Custom panel sizes possible

Prepreg

• 106 and 1067 styles available
• Enables bonding multilayer board stackups
• Matching resin system

Rod and Plate

• For machined parts, spacers, and non-PCB applications
• Reduces PIM in RF assemblies
• Ideal for fixtures and testing

This range covers the needs of most RF-35 PCB implementations from prototyping to production.

PCB Performance Capabilities

RF-35 laminate provides excellent RF and high speed digital performance when designed properly:

Frequency Range

• Usable continuous range from DC to Ku band (18 GHz)
• Material characterizations up to 40+ GHz
• Q factors exceeding 300 above 8 GHz

Loss

• Low loss tangent of 0.0019
• Insertion loss < 0.016 dB/inch at 20 GHz in 50Ω stripline

VSWR

• Tight dielectric constant tolerance enables excellent impedance control
• VSWR < 1.2 up to 15 GHz achievable

Propagation Delay

• Delay = 1.7 ns/inch typical at 50Ω
• Enables high data rates and rise time performance

Pulse Response

• TDR shows minimal discontinuities and reflections
• Clean time domain performance for ultra high-speed digital

Leveraging these attributes allows RF-35 PCBs to deliver highly repeatable RF and high speed digital operation.

Design Considerations

To obtain maximum benefit from RF-35 laminates, engineers should follow best design practices:

Stackup Planning

• Use multiple thinner cores instead of one thick core
• Alternating grain direction improves dimensional stability
• Model expected performance in solver

Impedance Control

• Leverage precise Er of 3.5 to maintain target impedance
• 50Ω striplines for RF and high-speed routing
• Controlled line width, dielectric height, trace geometry

Skin Effect

• Consider skin effect depth above ~ 8-10 GHz
• Utilize surface treatments like micro-etching

Signal Coupling

• Careful gap/spacing rules between traces
• Ground plane isolation techniques
• Avoid 90 ̊ bends; use arc/tapered geometries

Thermal Management

• Ensure sufficient thermal ground plane spreading
• Efficient component layout to avoid hotspots
• Consider thermal vias for heat transfer

Paying attention to these guidelines helps achieve first-pass PCB layout success with RF-35.

Recommended Stackups

Typical RF-35 PCB stackups may use configurations like:

Show Image

• Multiple thin dielectric cores
• Signal routing on surface layers
• Dedicated ground planes near signals
• Buried capacitance within stackup
• Component cavities in ground planes

The thin cores and smooth copper foils of RF-35 enable tight impedance tolerance and high performance interconnects between ICs, filters, amplifiers, control logic, and other components.

Benefits vs. FR4

Compared to conventional FR-4 laminates, RF-35 provides:

Superior Loss Characteristics

• Lower loss tangent: 0.0019 vs 0.02 for FR-4
• Much flatter loss vs. frequency curve
• Maintains low loss to > 10 GHz

Tighter Dielectric Constant Tolerance

• Tolerance +/- 0.05 vs +/- 0.25 for FR-4
• Enables consistent impedance across PCBs

Improved Moisture Resistance

• 0.02% moisture absorption vs 0.2% for FR-4
• Far less susceptible to humidity effects

Higher Frequency Support

• Usable range to Ku band vs drop-off around 5 GHz with FR-4
• Significantly better Q factors at high microwave bands

For peak signal integrity at microwave and mmWave frequencies, RF-35 is a clear choice over FR-4 material.

Typical RF-35 Applications

The capabilities of RF-35 make it a frequent choice for products including:

• Satellite communications
• Radar and remote sensing
• 5G telecom infrastructure
• Automotive radar
• Wireless networking
• Microwave radio/links
• Defense electronics
• Mobile devices
• High speed digital design
• Aerospace and avionics

Any application where optimizing signal integrity, reducing loss, and maintaining consistent performance over frequency are critical requirements will benefit from RF-35 PCB material.

Pros and Cons

Like any material, RF-35 has both advantages and disadvantages:

Pros

• Excellent high frequency signal integrity
• Low loss PTFE material
• Tight dielectric constant tolerance
• Lead-free assembly compatible
• Good thermal conductivity
• Reduced moisture absorption

Cons

• Higher cost than FR-4
• Lower flexural strength than glass-reinforced laminates
• Requires advanced fabrication processes
• Limited global supply chain

Conclusion

With its precise dielectric constant of 3.5 and low loss PTFE composition, Taconic RF-35 delivers proven performance for today’s emerging RF, microwave, and multi-gigabit digital designs. When engineered properly, RF-35 PCBs provide consistent behavior across fabrication lots and excellent high frequency response. For designers pursuing every last dB of loss or GHz of bandwidth, RF-35 remains an enabling material.

Frequently Asked Questions

Q: What are the key differences between RF-35 and common FR-4 laminates?

A: RF-35 provides much lower loss, tighter dielectric tolerance, lower moisture absorption, and extended high frequency range versus economical FR-4.

Q: What are some tips for working with thinner RF-35 cores?

A: Use dedicated layer alignment equipment, employ smaller component sizes, plan sufficient panelization spacing, and minimize handling to avoid cracking thin cores.

Q: Does RF-35 require special PCB fabrication processes?

A: RF-35 benefits from advanced PTFE processes for via formation, hole walls, and drilling. It also requires lamination processes tailored to thinner cores.

Q: What are typical finished RF-35 PCB thicknesses?

A: High frequency designs aim for overall PCB thickness under 0.030 inches. This requires precision lamination of multiple 0.005 inch dielectric cores.

Q: Are there lead-free soldering implications with RF-35 material?

A: RF-35 achieves high Tg (>280C) for compatibility with lead-free profiles up to 260C peak temperatures. Thermal relief in multilayers is recommended.

Do you know RF-35 (TACONIC material)?

Performance:

(1) low cost;

(2) Excellent peel strength;

(3) Extraordinary low loss factor;

(4) low water absorption rate;

(5) Enhanced surface smoothness.

Application:

(1) power amplifier;

(2) filters and connectors;

(3) Passive components.

1)RF-35 is an organic-ceramic laminate material in the ORCER of TACONIC products.

2)It is a reinforced glass material based on woven glass cloth, and a combination of TACONIC’s ceramic filling technology and glass fiber coated PTFE technology.

3)RF-35 is the best choice for low cost, high volume commercial microwave and wireless frequency applications.

3)RF-35 of 1/20Z and 10Z copper foil boards, even with standard epoxy materials, have excellent peel strength and provide rework at any time.

4)The glass transition temperature of RF -35 exceeds 315 ℃.

5)The ultra-low water absorption and low loss factor of RF-35 minimizes phase shift in the frequency range of use.

6)The dimensional stability of RF-35 is due to the use of woven glass cloth in its design development.

7)RF-35 laminate material, generally with single or double-sided 1/20Z, 10Z and 20Z thickness of electrolytic copper foil. Different sizes of sheets can be selected according to requirements.

8)For the RF-35 microwave material, the relationship between the thermal expansion rate in the Z-axis direction and the temperature is shown in the figure below:

9)RF-35 dielectric constant changes with temperature:

10)RF-35 dielectric loss changes with temperature:

10)The relationship between the dielectric constant and frequency of RF-35 microwave materials is shown in the figure below:

11)The relationship between the dielectric loss of RF and the frequency of microwave materials is shown in the figure below:

What is ffc wiring and what is  fpc wiring ?

Wiring, also known as flexible circuit board (FPC). It is used for the transmission of data within the active parts and areas, such as the hard disk connected to the mainboard of the computer, the data line of the optical drive, the data line of the mobile phone motherboard connected to the display screen, and so on. There are also connected devices between the data lines are collectively known as wiring. Wire layout is mainly divided into two kinds of round head (R-FFC for direct welding) and flat ends (for short FFC, for socket insertion). Most suitable for data transmission cables between moving parts and motherboards, between board and board, and for miniaturized electrical equipment. Because the price of FFC cable is better than that of FPC (flexible Printing Circuit), its application will become more and more extensive. In most places where FPC is used, you can basically replace it with FFC.

https://www.youtube.com/watch?v=pG2FsS7ZXuo

Wiring characteristics

1. The wire layout is small, light weight, the original design of the wiring board is used to replace the larger wire harness wire. Wiring is usually the only solution to miniaturization and mobility on the current cut TIng-edge assembly board. Wire placement (sometimes referred to as flexible printed circuit) is the etching of copper circuit or printed polymer thick film circuit on the polymer substrate. For thin, light, compact and complex devices, the design solutions range from single-sided conductive circuits to complex multi-layer three-dimensional prototype pcb assembly. The total weight and volume of wire arrangement is 70% less than the traditional round wire harness method. Wire placement can also increase strength by using reinforced materials or linings to achieve additional mechanical stability.
2. Wire placement can be moved, bent, twisted without damaging the wire, and can conform to different shapes and special package sizes. The only limitation is the volume space problem. Because it can withstand millions of times of dynamic bending, wiring can be well applied to continuous or periodic motion of the internal system, as part of the final product function. The solder joints on the rigid PCB are subjected to thermal mechanical stresses that fail after hundreds of cycles. “require electrical signals / power to move,” said Jenny, a product manager at EECX. Some products with smaller shape coefficients / package sizes benefit from wire placement.

3, wiring has excellent electrical properties and dielectric properties,” said the CEO of heat-resistant. LT Electronic. “low dielectric constants allow electrical signals to be transmitted quickly; Good thermal properties make the element easy to cool down; higher glass conversion temperature or melting point make the element work well at higher temperature.

4, wiring has higher assembly reliability and quality. Wiring reduces the hardware required for internal wiring, such as solder joints, trunk wires, backboard lines and cables commonly used in traditional electronic packaging, enabling wiring to provide higher assembly reliability and quality. Ping.Wu, a marketing manager with a higher misalignment rate of electronic components, said Ping.Wu, a marketing manager of. EECX Electronic Products Division, a market manager with complex multiple systems, said, “the stiffness of wiring is low and the size is small,” said Ping.Wu, the market manager of. EECX Electronic Products Division, which is composed of complex multiple systems. It is precisely because of the small size of the wiring board components, so the use of less material. ” With the emergence of quality engineering, a thin flexible system is designed to be assembled in only one way, thus eliminating many human errors usually associated with independent wiring engineering.

What is FFC wiring

FFC wiring is also called flexible flat cable, which can choose the number and spacing of wire arbitrarily, make the wire more convenient, greatly reduce the volume of electronic products, reduce production cost, improve production efficiency, and is most suitable for moving parts and motherboards. PCB board is used for data transmission cable between PCB boards and miniaturized electrical equipment. The common specifications are 0.5mm / 0.8mm / 1.0mm / 1.25mm / 1.27mm / 1.5mm / 2.0mm / 2.54mm and so on.

Line arrangement difference between FFC and FPC

FPC is the Flexible Printed Circuit flexible printed circuit, and in terms of their manufacturing, they are formed in a different way:

1, FPC is a kind of flexible circuit board with different single and double sides and multilayer pcb structure, which is treated by FCCL (flexible copper foil) by chemical etching.

2, FFC is made of flat copper foil with upper and lower layers of insulating foil film, the finished product is simple and the thickness is thicker.

Introduction

Printed circuit boards (PCBs) serve as the core component in virtually every electronic device. They provide the substrate to mount and interconnect electronic components using copper traces. To protect these copper traces from corrosion and ensure reliable solder joints, the copper pads are plated with solderable surface finishes.

ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold) has emerged as an advanced plating finish for PCBs, providing excellent solderability while also resisting corrosion. This article provides a comprehensive understanding of ENEPIG plating technology, its properties, process steps, pros and cons, and applications.

What is ENEPIG Plating?

ENEPIG or electroless nickel electroless palladium immersion gold plating is a PCB surface finish comprising of three metal platings deposited sequentially on copper pads – nickel, palladium and gold.

• Electroless nickel – Corrosion resistant layer
• Electroless palladium – Barrier layer prevents nickel diffusion
• Immersion gold – Outermost layer provides solderability

The term ‘electroless’ refers to autocatalytic deposition without using electrical current. The metals deposit through a chemical reduction reaction. ‘Immersion’ uses a chemical displacement reaction.

This tri-metal finish provides excellent solderability while also resisting corrosion and oxidation. It is an alternative to conventional finishes like electrolytic nickel/gold, immersion tin and OSP (Organic Solderability Preservatives).

Key Properties

• Excellent solderability and wettability
• Low and stable contact resistance
• Corrosion resistance comparable to gold
• Good wirebondability
• Lead-free solder compatibility
• Halogen-free formulation available

Why Use ENEPIG Plating?

ENEPIG plating offers following benefits over other PCB finishes:

1. Reliable Solderability

• Gold outer layer provides excellent solderability, similar to immersion gold.
• The underlying nickel and palladium enhance adhesion of the gold layer.

2. Lead-free Solder Compatibility

• Gold allows reliable lead-free soldering, unlike tin finishes which are prone to tin whiskers.
• Palladium barrier layer prevents diffusion of nickel into solder joint.

3. Corrosion Resistance

• The nickel underlayer provides corrosion resistance comparable to gold.
• Palladium isolates the nickel from the solder joint.

4. Halogen-free Formulations

• Electroless nickel and palladium use halogen-free chemistries, avoiding issues with immersion gold.

5. Contact Resistance Stability

• The nickel and palladium base preserves the low contact resistance of gold finishes.

6. Wire Bond Compatibility

• The gold layer allows reliable wire bonding.

7. Self-Limiting Thickness

• Immersion plating process provides self-limited uniform thickness.

ENEPIG Plating Process Steps

ENEPIG finish deposition involves sequential electroless plating of nickel, palladium and immersion gold:

1. Electroless Nickel Plating

• PCB undergoes dilute acid cleaning and microetching.
• Activated in palladium chloride to initiate nickel deposition.
• Electroless nickel plating solution deposits nickel through an autocatalytic chemical reaction.
• Thickness of 5 to 8 micro-inches nickel is plated.

2. Electroless Palladium Plating

• Nickel layer is activated in an acidic solution.
• Electroless palladium solution deposits a thin layer of palladium, typically 0.2 to 0.5 micro-inches.
• Palladium prevents diffusion of nickel into solder joint.

3. Immersion Gold Plating

• PCBs are dipped in immersion gold solution which contains gold salts.
• The gold displaces palladium through a galvanic exchange reaction.
• Gold layer of 0.1 to 0.5 micro-inches is plated.
• Provides solderability and wire bondability.

Comparison of ENEPIG vs Other Finishes

Parameters	ENEPIG	ENIG	Imm. Tin	OSP
Solderability	Excellent	Excellent	Good	Fair
Process Control	Moderate	Difficult	Easy	Easy
Lead-free solder compatible	Yes	Yes	Prone to whiskers	Yes
Corrosion resistance	Excellent	Moderate	Poor	Fair
Contact resistance	Low and stable	Unstable	Low	Moderate
Shelf life	12 months	6-9 months	4-6 months	3-6 months
Soldering heat resistance	Good	Fair	Excellent	Poor
Wirebond compatibility	Excellent	Excellent	Fair	Poor
Cost	Moderate	High	Low	Very low

Pros and Cons of ENEPIG Finish

Pros:

• Excellent solderability and contact reliability
• Resists corrosion as effectively as gold
• Compatible with lead-free solders
• Allows wire bonding
• Provides stable low contact resistance
• Halogen-free formulations available
• Self-limiting and uniform thickness

Cons:

• More expensive than tin, silver, OSP finishes
• Requires precise process control
• Palladium is expensive
• Multiple plating steps increase cycle time
• Shelf life shorter than tin finishes

Applications of ENEPIG Plating

The key applications where ENEPIG finish provides benefits are:

1. Lead-free Soldering

Compatible with lead-free solders, unlike tin finishes prone to whiskering.

2. Automotive Electronics

Withstands under-hood temperatures. Halogen-free for reduced outgassing.

3. Avionics and Aerospace

High reliability needed for extreme conditions.

4. Medical Electronics

Biocompatible finish.

5. Wireless and Portable Electronics

Supports lead-free soldering and tin whisker mitigation.

6. High Speed Digital Circuits

Gold provides low contact resistance stability.

7. Wire Bonding

The gold layer enables wire bonding.

ENEPIG Plating on Different PCB Pad Types

ENEPIG can be deposited on various finishes present on PCB pads:

Pad Type	Process
Bare Copper	Directly applies ENEPIG finish
Immersion Tin	Pre-activates with palladium before ENEPIG
Immersion Silver	Masks pad surface before ENEPIG deposition
OSP	Removes OSP completely prior to ENEPIG
Electrolytic Nickel Gold	Strips nickel and activates for ENEPIG process
Immersion Gold	Strips gold, activates nickel, then follows ENEPIG steps
Solder Mask Defined	Selectively strip solder mask before plating ENEPIG

Key Process Challenges with ENEPIG

Some process challenges associated with ENEPIG plating include:

• Uniformity: Electroless deposition depends on local chemical conditions. Careful monitoring and tank agitation is required.
• Palladium Activation: Insufficient activation can cause non-uniform nickel deposition and gold embrittlement.
• Bath Maintenance: Regular analysis and replenishment of electroless baths is critical.
• Solder Mask Adhesion: Compatibility between solder mask and ENEPIG chemistry must be ensured.
• Via Filling: Deposits thin coating only. For thicker coatings, additional electroless copper buildup may be required.

Frequently Asked Questions (FAQs)

Q1. Does ENEPIG finish contain any nickel on the surface?

No. The top surface is pure gold, with palladium and nickel below it. Palladium acts as diffusion barrier to isolate nickel from gold layer.

Q2. Can ENEPIG finish withstand multiple reflow cycles?

Yes, ENEPIG provides excellent soldering heat resistance. The underlying nickel and palladium enhance adhesion of the gold layer through repeated temperature cycling.

Q3. What is the typical thickness of ENEPIG finish?

Thickness values are: Nickel: 5-8 microinches, Palladium: 0.2-0.5 microinches, Gold: 0.1-0.5 microinches. Total thickness is usually under 1 micron.

Q4. Does ENEPIG allow both lead and lead-free soldering?

Yes, the gold outer layer of ENEPIG is highly solderable with both lead-based and lead-free solders. Underlying nickel and palladium enhance intermetallic formation.

Q5. Can ENEPIG finish withstand board assembly in wave soldering?

ENEPIG finish has adequate thermal resistance to withstand wave soldering processes, unlike PCB finishes like OSP which have poor heat resistance.

Printed circuit boards (PCB) need routine cleaning during manufacturing, rework and maintenance to remove contaminants like flux residues, dust, grease and other particles. Choosing the right circuit board cleaner is important to effectively remove contamination without damaging the board. This article discusses different types of PCB cleaners, how to select the appropriate one, cleaning methods and best practices.

Need for Cleaning Circuit Boards

Following are some key reasons for cleaning PCBs:

• Remove corrosive flux residues after soldering – These can degrade performance over time if not cleaned properly. No-clean flux also leaves minor residues.
• Eliminate dust, dirt and particulates – These can lead to short circuits or affect heat dissipation.
• Remove grease, oil and silicones – They can coat test pads or socket contacts hindering detection.
• Take off adhesive residues – From stickers or labels which may insulate traces.
• Get rid of oxidized copper and tarnishing – Can negatively impact soldering if not removed.
• Correct field failures by cleaning – Contamination is a common cause of field failures.
• Prepare boards for conformal coating – Coating adhesion relies on a pristine PCB surface.
• Allow inspection of boards – Cleaning facilitates easier visual inspection.

Proper cleaning is thus vital both during assembly and for maintenance of operational PCBs. Using the right cleaner avoids issues like corrosion while removing residues.

Properties of a Good PCB Cleaner

An effective PCB cleaner exhibits following desirable properties:

• Cleaning ability – Should thoroughly remove fluxes, pastes, greases, particles.
• Material compatibility – Should not damage board substrate, components, coatings.
• Residue-free cleaning – Should not leave any cleaner residues after rinsing.
• Quick drying – Fast evaporation allows quicker processing.
• Non-flammability – Important for safety given organic solvents.
• Minimal odor – Reduces environmental impact.
• Reusability – Allows multiple cleaning cycles improving economy.
• Accessibility – Easily available from supply sources.
• Low cost – Important considering regular use during production.

Types of Circuit Board Cleaners

Some common options for PCB cleaners include:

Aqueous Cleaners

• Water-based cleaners with detergents, pH modifiers.
• Non-flammable, biodegradable, usable at room temperature.
• May leave water residues requiring extra drying.
• Poor at removing some organic residues.

Semi-Aqueous Cleaners

• Contain mild solvents in water for added cleaning ability.
• Evaporate faster than aqueous cleaners.
• Less flammable than solvents. May still require rinsing.

Solvent Cleaners

• Strong organic solvents like acetone, isopropyl alcohol (IPA), methanol etc.
• Very effective at removing organic flux, greases, oils.
• Fast evaporation at room temperature. Highly flammable.
• Some chlorinated solvents like 1,1,1-Trichloroethane available but being phased out.

Terpene Cleaners

• Derived from pine, orange oils. Non-hazardous, non-flammable.
• Biodegradable but slower to evaporate than solvents.
• Weaker cleaning ability than solvents. Mostly used with frequent cleaning.

Engineered Cleaners

• Uses surfactants for cleaning combined with corrosion inhibitors.
• Provides both cleaning and temporary corrosion protection.
• Used as benchtop spray or inline cleaners.

Selecting the Right Circuit Board Cleaner

Selection criteria for PCB cleaners depends on application:

During Manufacturing

• Strongest cleaning ability preferred to remove all residues and maximize first-pass yield.
• Quick evaporation allows faster processing. Flammability addressed by safe storage.
• Low cost important as used routinely in every batch.
• Residue testing essential to avoid any cleaner vestiges.

Field Maintenance/Rework

• Strong cleaners used but with emphasis on safety. Accessibility in aerosol cans useful.
• Non-flammable, non-hazardous cleaners may be mandated.
• Cleaners with corrosion inhibitors help protect cleaned boards.
• Evaporation time and residues lesser concerns with one-off usage.

Cleaning Methods for Circuit Boards

Some ways PCB cleaners are applied:

Manual Cleaning

• Cleaner applied manually using brushes, swabs, wipes.
• Used for prototype, on-demand cleaning.
• Labor intensive but good for limited, selective cleaning.

Ultrasonic Bath

• PCBs immersed in cleaning solution tank which is ultrasonically agitated.
• Provides consistent, thorough cleaning. Particularly good for odd board shapes.
• Allows high volume batch cleaning.

Spray In Air

• Cleaner sprayed using nozzles onto PCB held in a fixture.
• Automated using a conveyorised system with multiple spray/rinse stations.
• Facilitates selective cleaning of areas. Fast.

Vapour Phase Cleaning

• PCB exposed to cleaning solvent vapours which condense selectively on cooler residues dissolving them.
• Very effective at removing even microscopic surface contaminants.
• No residues left from drying. Expensive equipment.

Dishwasher type Batch Cleaners

• PCBs loaded in a cabinet with spray nozzles.
• Automated cleaning cycles with various solutions and rinses.
• Moderate throughput suitable for small batches.

Water-based vs Solvent Circuit Board Cleaners

Water-based cleaners are safer and non-flammable but slower at removing organics while solvents evaporate faster but are hazardous. Hybrid semi-aqueous offer a compromise. Typical comparison:

Parameter	Water-based	Semi-aqueous	Solvent-based
Cleaning Ability	Medium	Medium-High	Very High
Drying Time	High	Medium	Very Low
Flammability	None	Low	High
Performance on Organics	Medium	Medium-High	Excellent
Performance on Ionics	Excellent	Medium	Low
Environmental Impact	Non-hazardous	Marginally hazardous	Hazardous
Health/Safety	Safe	Use with caution	Risk of burns, inhalation
Residues after Cleaning	High chance of water residues	Low chance	None usually
Typical Usage	Light cleaning	General purpose	Strong contamination

Key Considerations for Choosing Circuit Board Cleaner

• Type and extent of contamination to be removed
• Allowable flammability based on usage environment
• Evaporation rate and potential for residue formation
• Effect on board materials like plastics, coatings
• Whether ulrasonic cleaning is to be used
• Environmental regulations for effluents and disposal
• Health hazards to operators during use
• Cost, availability, reusability factors

Careful selection of the right cleaner and cleaning process ensures thorough contaminant removal without any detrimental effects on the boards or personnel.

Best Practices for Cleaning Circuit Boards

Some good practices when cleaning PCB assemblies:

• Test cleaner compatibility on a non-critical area first.
• Follow manufacturer recommended dilutions and usage guidelines.
• Apply cleaner using brushes, swabs for selective cleaning.
• Use higher temperatures to improve cleaner action but within limits.
• Rinse boards thoroughly with clean water or solvent post-cleaning.
• Dry boards immediately after rinsing using compressed air flow.
• Allow sufficient cleaning time for immersed or sprayed boards.
• Use cleaning fixtures to access difficult areas like connectors.
• Wear nitrile gloves to prevent skin contact and contamination.
• Ensure the cleaner is not expired and container is sealed properly after use.

Properly implementing the material and equipment manufacturers’ instructions helps maximize cleaning efficacy while minimizing any detrimental effects.

Troubleshooting Cleaning Issues

Some common PCB cleaning problems and remedies:

Issue	Possible Causes	Corrective Actions
Incomplete cleaning	Too dilute cleaner concentration	Increase cleaner strength
Insufficient cleaning time	Use longer immersion time
Low cleaning temperature	Increase solution temperature
Excessive contamination	Do multiple-stage cleaning
Cleaner leaving residues	Low rinsing	Rinse more thoroughly with water/solvent
Cleaner has surfactants	Select cleaner without surfactants
Evaporation issues	Blow dry boards instead of air drying
Corrosion observed after cleaning	No corrosion inhibitors in cleaner	Use cleaners containing inhibitors
Water residues left after rinsing	Dry immediately after rinsing
Discoloration of boards	Chemical attack by cleaner	Reduce concentration and exposure time
Overexposure to cleaner	Optimize cleaner application parameters

Careful inspection of the cleaned boards reveals most cleaning issues for troubleshooting based on board appearance and testing.

Conclusion

PCB cleaning is a critical process needing careful selection of the right chemistry and method. Aqueous, semi-aqueous and solvent-based cleaners each have specific strengths and weaknesses. Usage environment, board materials, residue tolerance, cost and environmental factors guide the cleaner choice. Following manufacturer recommendations and industry best practices for parameters like concentration, temperature and rinsing while testing on non-critical boards ensures effective contaminant removal without board or personnel hazards. Cleaning validation using ionic residue testing confirms the cleaning process is working adequately. With the growing complexity of boards requiring high first-pass yields, proper cleaning is becoming even more indispensable for quality and reliability.

FAQs

Q1. Can isopropyl alcohol (IPA) be used to clean circuit boards?

Yes, isopropyl alcohol is an excellent general purpose cleaner for PCBs due to its strong solvency power, rapid evaporation and low cost. Care must be taken regarding its flammability.

Q2. What is the ideal PCB cleaning temperature?

For water-based cleaners, 45-55°C is typically used. Some engineered cleaners work well at room temperature. Solvent cleaners are also usually used cold.

Q3. When should ultrasonic cleaning be used for PCBs?

Ultrasonic cleaning effectively removes particulate contamination and cleans blind vias and odd-shaped boards. It should be used as needed based on inspection.

Q4. What is a quick test to verify post-cleaning board cleanliness?

Using reverse osmosis/deionized water and measuring resistivity provides a good quick cleanliness verification method. High resistivity indicates the board is clean.

Q5. How can one improve the drying rate after aqueous cleaning?

Use of higher water temperatures, spray/air impingement rinses and immediate forced hot air drying after rinsing improves drying rate and prevents water residues.