Shengyi S1155 Mid-Tg FR-4: Datasheet, Properties & Design Tips

Selecting the right laminate for a modern PCB is no longer just about meeting a cost target. With environmental regulations tightening and lead-free assembly becoming the global standard, engineers are increasingly looking for “Halogen-Free” materials that don’t sacrifice processability or thermal reliability.

Shengyi S1155 is a mid-Tg, halogen-free FR-4 laminate that has become a staple for engineers who need a “green” material without the headaches often associated with high-Tg specialty substrates. In this guide, we will dive into the technical datasheet, compare its performance to standard FR-4, and provide practical design tips for integrating S1155 into your next stackup.

What is Shengyi S1155?

Shengyi S1155 is a high-performance, halogen-free, and lead-free compatible FR-4 material. It is engineered to meet the IPC-4101/21 specification sheet, offering a balance of environmental compliance and robust thermal properties.

Unlike conventional FR-4 (like S1141), S1155 does not contain toxic halogens (Bromine or Chlorine), Antimony, or Red Phosphorus. This makes it a preferred choice for companies adhering to strict “Green” initiatives while requiring a material that can withstand the high-temperature peaks of lead-free reflow cycles.

Key Features of S1155

Halogen-Free: Complies with JPCA-ES-01-2003 standards for green electronics.

Lead-Free Compatible: Specifically designed for assembly processes utilizing SAC305 and other lead-free solders.High Thermal Resistance: Boasts a decomposition temperature (Td) significantly higher than standard FR-4.

Excellent CAF Resistance: Enhanced resin chemistry improves Conductive Anodic Filament resistance, making it suitable for high-density designs.

UV Blocking & AOI Compatible: Seamlessly integrates into standard fabrication workflows.

Shengyi S1155 Technical Datasheet Overview

As an engineer, the “Typical Values” on a datasheet are your guardrails. Below are the critical parameters for S1155 that will define its behavior in your CAD software and on the assembly line.

Thermal & Mechanical Properties

The thermal robustness of S1155 is its standout feature, particularly its Td and delamination times.

Property	Test Method	Typical Value	Engineering Significance
Tg (DSC)	IPC-TM-650 2.4.25	140°C	The point where the material softens.
Td (TGA 5% W.L.)	IPC-TM-650 2.4.24.6	380°C	High headroom for multiple reflows.
T260 (Delamination)	IPC-TM-650 2.4.24.1	60+ Minutes	Incredible resistance to pad cratering.
T288 (Delamination)	IPC-TM-650 2.4.24.1	60+ Minutes	Far exceeds standard FR-4 (usually <10m).
CTE (Z-axis, Pre-Tg)	IPC-TM-650 2.4.24	41 ppm/°C	Low expansion protects via barrels.
CTE (Z-axis, Post-Tg)	IPC-TM-650 2.4.24	235 ppm/°C	Moderate expansion at high temps.
Water Absorption	IPC-TM-650 2.6.2.1	0.10%	Very low; prevents “popcorning.”

Electrical Properties

While S1155 isn’t marketed as a “high-speed” low-loss material, it provides a stable dielectric constant (Dk) and dissipation factor (Df) that are superior to many mid-Tg counterparts.

Property	Condition	Typical Value
Dielectric Constant (Dk)	1GHz (RC 55%)	4.22
Dissipation Factor (Df)	1GHz (RC 55%)	0.011
Volume Resistivity	After Moisture	2.52 x 10⁸ MΩ-cm
Surface Resistivity	After Moisture	3.68 x 10⁷ MΩ
Dielectric Breakdown	D-48/50+D-0.5/23	55 kV

Design Tips for Engineers using S1155

Integrating S1155 into your design requires a slight shift in how you view the stackup and fabrication.

1. Stackup Planning and Impedance Control

S1155 has a Dk of approximately 4.22 at 1GHz (at 55% resin content). This is slightly lower than standard FR-4 (usually 4.5–4.7). If you are transitioning a design from a standard <a href=”https://www.pcbsync.com/Shengyi-pcb/“>Shengyi PCB</a> material like S1141 to S1155, you must recalculate your trace widths to maintain impedance. Failing to do so could result in a 5–8% mismatch.

2. Microvia Reliability

The Z-axis CTE of S1155 (41 ppm/°C before Tg) is excellent for a mid-Tg material. However, for boards with stacked microvias or layer counts exceeding 10 layers, always check with your fabricator regarding the aspect ratio. S1155 is highly reliable for PTH (Plated Through Hole) but should be handled carefully in ultra-thin HDI designs.

3. Thermal Management

Because S1155 has such a high Td (380°C), it is much more “forgiving” of manual rework than standard FR-4. If your board requires heavy hand-soldering of large connectors or high-mass components, S1155 will significantly reduce the risk of pad delamination or localized scorching.

4. Copper Weight Considerations

S1155 supports copper foil weights up to 105µm (3oz). For power electronics, the high thermal resistance of this material makes it a great choice for boards that will run “hot” but don’t quite require a high-Tg substrate like S1000-2.

S1155 Applications and Use Cases

Where should you specify S1155? Based on its halogen-free nature and thermal profile, it dominates in several key sectors:

Consumer Communication: Routers, switches, and base station modules where environmental regulations (like RoHS and REACH) are strictly enforced.

Instrumentation & Medical: Diagnostic equipment that requires long-term signal stability and low moisture absorption.

Computer & Networking: Servers and peripherals where mid-range signal integrity is required alongside lead-free assembly.

Automotive Electronics: Infotainment and dashboard controllers that need to survive repeated thermal cycles in non-extreme environments.

S1155 vs. Standard FR-4: The Engineering Trade-off

If S1155 is so good, why use anything else? The answer, as always, is cost and stiffness.

Patents and research suggest that halogen-free materials like S1155 can sometimes exhibit slightly lower rigidity (stiffness) compared to standard DICY-cured FR-4 (like S1141). This means that for very large, thin panels, warpage control becomes critical during the baking and reflow stages. Always ensure your design utilizes a balanced stackup with symmetrical copper distribution to mitigate this.

Useful Resources for Readers

Shengyi Technology Official Product Center: The source for the latest official TDS and safety certificates. Visit Sytech

UL iQ Database: Use UL File Number E109769 to verify the flammability and thermal ratings for S1155. UL Search

IPC-4101 Standard: S1155 falls under slash sheet /21. Reviewing this will give you the industry-minimum performance requirements.

Frequently Asked Questions (FAQs)

1. Is Shengyi S1155 considered a “High-Tg” material?

No, S1155 is technically a Mid-Tg material with a Tg of 140°C. However, its thermal decomposition temperature (Td) of 380°C is comparable to many High-Tg materials, giving it superior lead-free reliability.

2. Can I use S1155 for high-speed digital designs?

Yes, up to a point. With a Df of 0.011 at 1GHz, it performs better than basic FR-4. It is suitable for signals like DDR3/4 and PCIe Gen 3, but for 25Gbps+ or high-frequency RF, you should look at Shengyi’s high-speed line (e.g., S7439).

3. What is the difference between S1155 and S1165?

S1165 is the “High-Tg” version of the halogen-free line (Tg 170°C). If your application involves high-layer-count HDI or extreme operating environments, S1165 is the better choice. For most consumer/industrial applications, S1155 is more cost-effective.

4. Why is S1155 noted for having “excellent CAF resistance”?

Halogen-free resins generally have a different molecular structure that forms fewer hydrogen bonds with water. This results in lower moisture absorption and a stronger bond between the resin and the glass fibers, which is the primary path for Conductive Anodic Filament (CAF) growth.

5. Does S1155 require special drilling parameters?

Generally, no. One of the benefits of S1155 is that its processing is very similar to conventional FR-4. Fabricators do not usually need to swap out drill bits or drastically change feed rates, which helps keep fabrication costs low.