FR4 Tg 170 PCB Explained: Specifications, Benefits & High-Temperature Applications

In the PCB material hierarchy, 170°C isn’t just another number — it’s the industry-recognized threshold that separates standard materials from high-performance substrates. When your design involves automotive under-hood electronics, aerospace avionics, or high-power industrial systems, Tg 170 PCB becomes the baseline for reliable operation rather than an upgrade option.

After spending years specifying materials for everything from consumer gadgets to military-grade systems, I can tell you that understanding when and why to use high-Tg materials separates successful designs from field failures. This guide covers everything engineers need to know about Tg 170 PCB — from specifications to real-world applications.

What is Tg 170 PCB? The High-Tg Threshold Explained

The “Tg” in Tg 170 PCB stands for Glass Transition Temperature — the point where the FR4 substrate transitions from a rigid, glass-like state to a softer, more pliable condition. At 170°C, this material begins its phase change, but critically, it maintains structural integrity far longer than standard alternatives under thermal stress.

According to IPC-4101 standards, the industry classifies FR4 materials into three tiers based on glass transition temperature:

Classification	Tg Range	Industry Designation
Standard/Low Tg	130-140°C	Basic FR4
Medium Tg	150-165°C	Mid-Tg FR4
High Tg	≥170°C	High-Tg FR4, Tg 170, Tg 180

The 170°C threshold matters because it represents a significant jump in material performance. High-Tg materials use enhanced resin systems with denser molecular cross-linking, resulting in superior thermal stability, lower Z-axis expansion, and better resistance to the stresses of modern lead-free assembly processes.

Why 170°C Became the Industry Standard

The 170°C benchmark didn’t happen by accident. It emerged from practical requirements:

Lead-Free Soldering: RoHS compliance pushed reflow temperatures from 210-230°C (tin-lead) to 240-260°C (lead-free). Standard Tg 130 materials experience significant stress at these temperatures, while Tg 170+ materials handle the thermal excursion with margin to spare.

Multilayer Reliability: Complex 10+ layer boards undergo multiple lamination cycles at 180-200°C. High-Tg materials maintain dimensional stability through these repeated thermal exposures.

Operating Environment: Modern electronics in automotive, industrial, and aerospace applications routinely operate at 100-150°C ambient temperatures. The 25-30°C safety margin below Tg makes 170°C the minimum for these environments.

FR4 Tg 170 Technical Specifications

Understanding the technical specifications helps you evaluate whether Tg 170 PCB meets your design requirements. These values represent typical ranges across major manufacturers.

Thermal Properties

Property	Typical Value	Test Method	Comparison to Tg 130
Glass Transition Temp (Tg)	170-175°C	DSC (IPC-TM-650)	+40°C higher
Decomposition Temp (Td)	340-350°C	TGA (5% weight loss)	+30-40°C higher
CTE (X/Y axis)	12-14 ppm/°C	IPC-TM-650	Similar
CTE (Z axis) below Tg	40-55 ppm/°C	IPC-TM-650	15-25% lower
CTE (Z axis) above Tg	150-180 ppm/°C	IPC-TM-650	20-30% lower
Thermal Conductivity	0.3-0.4 W/m·K	—	Similar
T260 (Time to Delamination)	>60 minutes	IPC-TM-650	2x longer
T288 (Time to Delamination)	>30 minutes	IPC-TM-650	2x longer
Max Operating Temperature	~145°C	—	+40°C higher

Electrical Properties

Property	Typical Value	Test Method
Dielectric Constant (Dk) @ 1MHz	4.2-4.5	IPC-TM-650
Dissipation Factor (Df) @ 1MHz	0.015-0.020	IPC-TM-650
Volume Resistivity	10⁸-10¹⁰ MΩ·cm	IPC-TM-650
Surface Resistivity	10⁷-10⁹ MΩ	IPC-TM-650
Dielectric Breakdown	45-55 kV/mm	IPC-TM-650
CTI (Comparative Tracking Index)	≥175V	IPC-TM-650

Mechanical Properties

Property	Typical Value	Test Method	Notes
Tensile Strength	420-480 MPa	IPC-TM-650	5-10% higher than Tg 130
Flexural Strength (25°C)	520-580 MPa	IPC-TM-650	Better rigidity
Flexural Strength (150°C)	340-400 MPa	IPC-TM-650	Maintains strength at temp
Peel Strength	1.0-1.4 N/mm	IPC-TM-650	Good copper adhesion
Moisture Absorption	≤0.10%	IPC-TM-650	Low absorption
Flammability	UL94 V-0	UL	Self-extinguishing

Key Benefits of Tg 170 PCB Material

The enhanced specifications translate into real-world performance advantages. Here’s what high-Tg material delivers for demanding applications.

Superior Lead-Free Soldering Performance

This is the primary driver for Tg 170 PCB adoption. Lead-free soldering creates thermal stresses that standard materials struggle to handle:

Assembly Scenario	Standard Tg 130	High Tg 170
Single reflow cycle	Marginal	Excellent
Double-sided reflow	Stressed	Very Good
Multiple reflow (rework)	Not Recommended	Good
Wave soldering	Acceptable	Excellent
Resin weight loss per cycle	1.5-3%	<0.5%

The higher decomposition temperature (Td ~340°C vs ~310°C) means less resin degradation during the 240-260°C lead-free reflow peaks. This translates to fewer assembly defects and improved long-term reliability.

Lower Coefficient of Thermal Expansion

The Z-axis CTE improvement is critical for via reliability and component attachment:

Below Tg: Tg 170 materials exhibit 40-55 ppm/°C Z-axis expansion compared to 55-70 ppm/°C for standard FR4. This 20-25% reduction decreases stress on plated through-holes during thermal cycling.

Above Tg: When temperatures exceed Tg (during soldering), standard materials can spike to 200-250 ppm/°C expansion. High-Tg materials stay in the 150-180 ppm/°C range, significantly reducing barrel cracking risk in vias.

Enhanced Dimensional Stability

High-Tg materials maintain tighter dimensional tolerances during PCB manufacturing:

• Better layer-to-layer registration in multilayer stackups
• Reduced bow and twist after lamination
• More consistent impedance control
• Improved fine-pitch component alignment

Improved Moisture and Chemical Resistance

The denser resin cross-linking in Tg 170 materials provides:

• Lower moisture absorption rates
• Better resistance to processing chemicals
• Reduced susceptibility to Conductive Anodic Filament (CAF) formation
• Longer shelf life before assembly

Anti-CAF Performance

CAF (Conductive Anodic Filament) formation causes electrical shorts through copper migration along glass fibers. This failure mode is accelerated by moisture, voltage, and temperature. High-Tg materials with enhanced resin systems significantly reduce CAF susceptibility — a critical factor for high-reliability applications with long service life requirements.

Tg 170 PCB vs Tg 130 vs Tg 150 vs Tg 180: Comprehensive Comparison

Choosing the right Tg level requires balancing performance requirements against cost and manufacturability.

Side-by-Side Comparison Table

Factor	Tg 130	Tg 150	Tg 170	Tg 180
Material Cost	Baseline	+5-10%	+15-25%	+20-30%
Max Operating Temp	~105°C	~125°C	~145°C	~155°C
Lead-Free Margin	Marginal	Good	Excellent	Excellent
Z-axis CTE	High	Moderate	Low	Very Low
Td (Decomposition)	~310°C	~320°C	~340°C	~350°C
Multilayer Support	≤8 layers	≤12 layers	≤20+ layers	≤24+ layers
Drilling Difficulty	Easy	Easy	Moderate	More Difficult
Availability	Excellent	Very Good	Good	Good
Anti-CAF	Standard	Improved	Very Good	Excellent

When to Use Each Tg Level

Tg 130 (Standard FR4):

• Basic consumer electronics
• Operating temperatures below 100°C
• Simple 2-4 layer designs
• Cost-critical applications
• Tin-lead soldering (legacy processes)

Tg 150 (Mid-Tg):

• Industrial controls at ambient temperature
• Automotive interior electronics
• 4-10 layer moderate complexity designs
• Lead-free assembly with single/double reflow
• Budget-conscious industrial applications

Tg 170 (High-Tg):

• Automotive under-hood electronics
• Industrial equipment in elevated temperatures
• Aerospace and defense systems
• 10+ layer complex multilayer designs
• High-reliability commercial products
• LED lighting with high heat dissipation
• Server and networking equipment

Tg 180+ (Premium High-Tg):

• Mission-critical aerospace/military
• Extreme temperature environments
• Maximum reliability requirements
• Very high layer count (20+ layers)
• Multiple sequential lamination cycles

Read more Different PCB Tg types:

High-Temperature Applications for Tg 170 PCB

The Tg 170 PCB finds its home in applications where thermal performance is non-negotiable. Here are the primary industries and use cases.

Automotive Electronics

Modern vehicles contain extensive electronics operating in challenging thermal environments:

Under-Hood Applications (Tg 170 required):

• Engine Control Units (ECUs)
• Transmission controllers
• Powertrain electronics
• Underhood sensors
• Battery Management Systems (EV/Hybrid)
• DC-DC converters

Ambient temperatures in engine compartments can reach 125-150°C, with thermal spikes even higher. Tg 170 material provides the necessary margin for reliable operation.

Interior Applications (Tg 150-170):

• Advanced Driver Assistance Systems (ADAS)
• Infotainment systems
• Instrument clusters
• Body control modules

Aerospace and Defense

Aerospace applications demand the highest reliability under extreme conditions:

• Avionics systems
• Flight control computers
• Radar and communication systems
• Satellite electronics
• Navigation equipment
• Missile guidance systems

These systems experience temperature ranges from -55°C at altitude to 100°C+ on the ground, often with rapid thermal cycling. Tg 170+ materials maintain dimensional stability through these transitions.

Industrial Automation

Factory floor equipment operates in harsh thermal environments:

• Motor drives and inverters
• PLC controllers
• Robotics control systems
• Furnace and oven controls
• Process automation equipment
• Power distribution systems

Telecommunications Infrastructure

5G and network equipment generates significant heat during continuous operation:

• 5G base station controllers
• High-speed routers and switches
• Optical transceivers
• Data center equipment
• Server motherboards

LED and High-Power Lighting

LED drivers and controllers experience sustained elevated temperatures:

• High-brightness LED drivers
• Outdoor lighting controllers
• Industrial lighting systems
• Automotive lighting

Many engineers choose Tg 170 FR4 over metal-core PCB (MCPCB) for LED applications where the thermal requirements don’t justify the MCPCB cost premium.

Medical Devices

Equipment requiring sterilization or operating in demanding environments:

• Surgical instruments (autoclave exposure)
• Medical imaging equipment
• Patient monitoring devices
• Diagnostic equipment

Design Guidelines for Tg 170 PCB

Proper design practices maximize the benefits of high-Tg material.

Layer Stack Recommendations

Tg 170 material excels in complex multilayer constructions:

Layer Count	Typical Thickness	Tg 170 Suitability	Notes
4 layers	1.0-1.6mm	Excellent	Often overkill unless thermal
6 layers	1.2-2.0mm	Excellent	Good balance
8 layers	1.4-2.4mm	Excellent	Standard for complexity
10 layers	1.6-2.4mm	Very Good	High-Tg recommended
12-14 layers	1.8-3.2mm	Very Good	High-Tg required
16-20 layers	2.0-3.2mm	Good	Consider Tg 180
20+ layers	2.4-4.0mm	Acceptable	Tg 180 preferred

Via Design for High-Tg Materials

The improved Z-axis CTE of Tg 170 material allows more aggressive via designs, but good practices still apply:

• Aspect ratio: Maintain below 12:1 for reliable plating
• Via diameter: 0.15mm minimum for laser drilling; 0.25mm+ for mechanical
• Thermal vias: Use arrays under hot components (0.3mm diameter, 0.8-1.0mm pitch)
• Via-in-pad: Fully supported with proper filling and planarization

Thermal Management Integration

Even with high-Tg material, proper thermal design extends board life:

1. Copper pours: Maximize exposed copper for heat spreading
2. Thermal via arrays: 25-30 vias per cm² under high-power components
3. Heavy copper option: Consider 2oz+ copper for power planes
4. Component placement: Distribute heat sources; avoid thermal concentration

Manufacturing Considerations

High-Tg materials require adjusted fabrication parameters:

Process	Standard FR4	Tg 170 FR4
Lamination temperature	175-185°C	185-200°C
Lamination pressure	Standard	+10-15% higher
Lamination cycle time	90-120 min	120-150 min
Drill bit wear	Normal	Faster (harder material)
Drill spindle speed	Standard	Reduced 10-15%

Communicate with your fabricator about using Tg 170 material — they may need to adjust process parameters for optimal results.

Common Tg 170 Material Options

Several manufacturers produce high-quality Tg 170 PCB materials. Here are commonly specified options:

Manufacturer	Material	Tg (DSC)	Td	Key Features
Shengyi	S1170	170°C	340°C	Industry standard, good availability
Shengyi	S1000-2	170°C	340°C	Enhanced version, better CAF
ITEQ	IT-170	170°C	340°C	Good electrical properties
ITEQ	IT-180A	180°C	350°C	Premium option
Isola	IS420	170°C	340°C	Aerospace/defense qualified
Isola	FR406	170°C	340°C	Widely available
Nan Ya	NP-170	170°C	335°C	Cost-effective option
Panasonic	R-1755V	175°C	350°C	Low CTE variant
Ventec	VT-47	175°C	340°C	Good HDI support

When specifying materials, always request the manufacturer’s datasheet and verify specific values for your application requirements.

Cost Factors for Tg 170 PCB

Understanding cost implications helps you budget accurately and justify material selection.

Material Cost Premium

Material Grade	Relative Cost	Notes
Standard Tg 130	1.0x (baseline)	Most economical
Mid Tg 150	1.05-1.10x	Modest premium
High Tg 170	1.15-1.25x	Significant premium
High Tg 180+	1.20-1.35x	Premium materials

Additional Manufacturing Costs

Beyond material pricing, Tg 170 PCB incurs additional manufacturing considerations:

Factor	Cost Impact	Reason
Longer lamination cycles	+5-10%	Higher temp, longer cure
Drill bit consumption	+10-15%	Harder material = faster wear
Process setup	Minor	Parameter adjustments
Lead time	+1-3 days	Specialized processing

When the Premium is Justified

The 15-25% material premium is justified when:

• Field failure costs exceed material savings
• Operating temperatures require thermal margin
• Lead-free assembly reliability is critical
• Multilayer complexity demands dimensional stability
• Application standards mandate high-Tg material
• Product lifetime expectations are long (10+ years)

Quality Control and Testing for Tg 170 PCB

Proper testing ensures your Tg 170 PCB meets performance requirements and application standards.

Material Verification

Before production, verify laminate quality:

• Request Certificate of Compliance (CoC) from laminate supplier
• Confirm Tg value using DSC measurement method
• Verify Td, CTE, and T260/T288 values against specifications
• Check moisture content for stored materials

Fabrication Quality Checks

Test	Purpose	Standard
Cross-section analysis	Via quality, plating thickness	IPC-6012
Thermal stress test	Delamination resistance	IPC-TM-650 2.6.8
Solder float test	Assembly compatibility	IPC-TM-650 2.4.13
Bow and twist	Dimensional flatness	IPC-TM-650 2.4.22
Impedance testing	Signal integrity	IPC-TM-650 2.5.5.7

Reliability Testing

For high-reliability applications, additional testing may include:

• Thermal cycling: -40°C to +125°C for automotive; -55°C to +125°C for aerospace
• Highly Accelerated Life Testing (HALT): Stress screening for design validation
• CAF testing: IPC-TM-650 2.6.25 for moisture resistance
• IST (Interconnect Stress Testing): Via reliability under thermal stress

Useful Resources for PCB Engineers

Industry Standards

• IPC-4101: Specification for Base Materials for Rigid and Multilayer Printed Boards
• IPC-6012: Qualification and Performance Specification for Rigid Printed Boards
• IPC-TM-650: Test Methods Manual

Material Datasheets

• Shengyi S1170/S1000-2 Datasheet: High-Tg FR4 specifications
• ITEQ Material Selector: IT-170, IT-180A specifications
• Isola Laminate Guide: IS420, FR406 specifications

Design Tools

• Saturn PCB Toolkit: Free thermal via and impedance calculator
• IPC-2152: Current carrying capacity standard

Frequently Asked Questions About Tg 170 PCB

What is the maximum operating temperature for Tg 170 PCB?

The practical maximum continuous operating temperature is approximately 140-145°C. Industry guidance suggests operating at least 25-30°C below the Tg value for long-term reliability. Brief temperature excursions during soldering (240-260°C for lead-free) are acceptable since they’re transient, but sustained operation near Tg accelerates material degradation.

Is Tg 170 PCB required for lead-free soldering?

Not absolutely required, but strongly recommended for reliable lead-free assembly. Standard Tg 130 materials can survive lead-free reflow, but they experience significant stress and resin weight loss (1.5-3% per cycle). Tg 170 materials handle lead-free temperatures with minimal degradation (<0.5% weight loss), making them essential for products requiring multiple reflow cycles, rework capability, or high long-term reliability.

How many layers can be reliably manufactured with Tg 170 material?

Tg 170 material reliably supports 20+ layer designs. The improved dimensional stability and lower thermal expansion make it the standard choice for complex multilayer boards with 10+ layers. For very high layer counts (24+ layers) requiring multiple sequential laminations, some engineers prefer Tg 180+ materials for additional thermal margin during repeated processing.

What’s the difference between Tg and Td in PCB materials?

Tg (Glass Transition Temperature) is the point where the material transitions from rigid to flexible — this change is reversible when cooled. Td (Decomposition Temperature) is where the resin chemically breaks down, losing mass — this is irreversible and permanent. For high-reliability applications, both values matter: high Tg maintains mechanical stability during operation, while high Td ensures survival during lead-free soldering without permanent damage.

When should I choose Tg 180 instead of Tg 170?

Consider Tg 180+ when: operating temperatures consistently exceed 130°C, your design requires 20+ layers with multiple lamination cycles, the application is aerospace/military grade with maximum reliability requirements, or thermal cycling is extreme (wide temperature swings). For most high-temperature industrial and automotive applications, Tg 170 provides adequate margin at lower cost. The Tg 180 premium is best reserved for truly demanding scenarios.

Conclusion: Making the Right Tg 170 PCB Decision

The Tg 170 PCB represents the entry point into high-performance PCB materials. It’s not the most expensive option, but it delivers the thermal stability, dimensional control, and assembly reliability that demanding applications require.

Use Tg 170 PCB when:

• Operating temperatures exceed 100°C sustained
• Lead-free assembly with reliability requirements
• Multilayer designs with 10+ layers
• Automotive under-hood or aerospace applications
• High-power electronics with thermal management needs
• Products with long service life expectations

Standard Tg 130 may suffice when:

• Operating temperatures stay below 85°C
• Simple 2-6 layer consumer electronics
• Cost is the primary constraint
• Short product lifecycle

The 15-25% material cost premium for Tg 170 is insurance against field failures, assembly defects, and reliability issues. For applications where performance and reliability matter, it’s typically money well spent.

When in doubt, discuss your specific application with your PCB fabricator and laminate supplier. They can provide guidance based on your operating conditions, assembly process, and reliability requirements. The right material choice at the design stage prevents expensive problems later.

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This guide reflects practical engineering experience with high-Tg PCB material selection. Specific properties vary by manufacturer — always verify values against your laminate supplier’s current datasheet for production material.