BT Resin IC Substrate
Dk 3.4-4.0 | Tg 185-225C | BGA/CSP standard — the Mitsubishi-developed resin system underlying most flip-chip and BGA package substrates.
3.4-4.0
Dk @ 1 GHz
185-225
Tg (C)
BGA/CSP
Primary Use
Mitsubishi
Origin
What is BT Resin Substrate?
BT (Bismaleimide Triazine) resin, developed by Mitsubishi Gas Chemical, is the dominant substrate material for semiconductor IC packaging — the thin circuit boards inside BGA, CSP, and flip-chip packages that route signals between the silicon die and the PCB. Over 70% of organic IC package substrates use BT-based laminate systems.
BT resin provides the high glass transition temperature (185-225C), low moisture absorption, and fine-line patterning capability required for IC package substrate fabrication. Its thermal stability survives the multiple reflow cycles that package assembly demands — die attach reflow, underfill cure, lid attach, and final board-level reflow.
The IC package substrate market represents a specialized segment between PCB fabrication and semiconductor wafer processing. Line widths of 10-30um (versus 75-100um for standard PCB) and via diameters of 50-100um (versus 200-300um for PCB) demand clean-room fabrication environments and advanced photolithography.
High Tg 185-225C
Survives multiple reflow cycles during package assembly.
Fine Line 10-30um
Advanced lithography enables high-density signal routing.
Low Moisture <0.5%
Prevents popcorn cracking during package-level reflow.
Industry Standard
70%+ market share in organic IC package substrates.
BT Resin Substrate Key Properties
Representative values from the manufacturer datasheet.
| Property | Value | Why it matters |
|---|---|---|
| Dielectric constant (Dk) | 3.4-4.0 @ 1 GHz | Suitable for IC package signal routing. |
| Dissipation factor (Df) | 0.004-0.010 @ 1 GHz | Adequate for package-level interconnect lengths. |
| Glass transition (Tg) | 185-225 C (DSC) | Multiple reflow survivability for package assembly. |
| Moisture absorption | 0.3-0.5% | Low uptake prevents MSL delamination and popcorning. |
| CTE x/y | 12-16 ppm/C | Moderate — managed with underfill for die CTE matching. |
| Line/space capability | 10/10 to 30/30 um | SAP and MSAP patterning for high-density routing. |
| Via diameter | 50-100 um laser | Microvia and stacked via for vertical interconnect density. |
| Layer count | 2-12 layers | From simple 2L CSP to complex 12L flip-chip substrates. |
| Core thickness | 40-200 um | Ultra-thin cores for package height reduction. |
BT Substrate in Modern IC Packaging
Every BGA package in your computer — CPU, GPU, memory, chipset — sits on a BT resin substrate. The substrate redistributes the fine-pitch die bumps (40-130um pitch) to the coarser BGA ball array (400-1000um pitch) that interfaces with the main PCB. This fan-out routing is the fundamental function of the package substrate.
Modern BT substrates have evolved far beyond simple redistribution. They now incorporate embedded passives (capacitors, resistors), stacked microvias for vertical routing density, and asymmetric constructions optimized for warpage control during package assembly. 8-12 layer BT substrates support the most complex server and networking ASICs.
The substrate industry is transitioning from legacy subtractive patterning (50um L/S minimum) to SAP (Semi-Additive Process) enabling 10-15um L/S. This enables higher I/O density, smaller package footprints, and denser signal routing for next-generation chiplet architectures.
IC Package Standard
Underneath every BGA in computing, mobile, and networking devices.
Stacked Microvias
Vertical routing density matching die bump pitch requirements.
SAP Fine-Line
10-15um L/S for next-generation chiplet routing density.
Embedded Components
Passives integrated into substrate for power delivery optimization.
IC Package Substrate Comparison
BT resin versus alternative package substrate technologies.
| Material | Dk | Df | Best For |
|---|---|---|---|
| BT Resin (Standard)This page | 3.8 | 0.008 | Mainstream BGA/CSP — 70%+ market share, proven. |
| BT Resin (Low-Loss) | 3.4 | 0.004 | High-speed packages — HBM, networking ASIC. |
| ABF (Ajinomoto) | 3.0 | 0.004 | Ultra-fine L/S — chiplet interposers, advanced nodes. |
| Glass Core | 4.6 | 0.003 | CTE-matched — AI accelerator, HBM interposer. |
| LTCC Ceramic | 7-8 | 0.002 | Hermetic — military, space, extreme reliability. |
BT Resin Substrate Applications
BGA substrates, flip-chip packages, CSP interposers, memory module substrates, SiP package carriers
Processor Packages
Desktop, server, and mobile CPU BGA substrates.
ASIC Packages
Networking, AI accelerator, and custom ASIC substrates.
Memory Packages
DDR5, HBM, and storage controller BGA substrates.
5G RF Modules
System-in-Package (SiP) substrates for 5G front-end modules.
Automotive SiP
ADAS processor and sensor fusion package substrates.
Medical Sensors
Compact sensor SiP packages for implantable and portable medical.
BT Substrate Design Guidelines
BT substrate design follows IC packaging rules rather than PCB rules. Minimum features are defined by the fabricator's SAP or MSAP capability (typically 15-30um L/S for production). Work closely with the substrate vendor's DFM team during layout — their process capability defines your routing density.
Warpage management is critical for BT substrates. Asymmetric copper distribution between top and bottom causes bow during reflow. Design copper balance within 15% between sides, and work with the substrate vendor to select appropriate core/prepreg combinations for your specific package construction.
Get Instant QuoteFollow IC Package Rules
15-30um L/S production. Work with vendor DFM for layout.
Warpage Management
Balance copper within 15% between sides for flat packages.
Microvia Stack Planning
Max 3-4 stacked microvias without fill reliability risk.
MSL Compliance
Design for MSL-3 minimum to avoid moisture-related failures.
Genuine BT Resin Substrate, Verified on Every Order
Material CoC
Certificate of Conformance with lot number ships with every order.
Stock Verified
We confirm laminate availability before order confirmation.
No Substitutions
Specified material guaranteed — never swapped without written approval.
FAQ
BT Resin Substrate Questions
What is BT resin substrate?
A Bismaleimide Triazine resin system (developed by Mitsubishi Gas Chemical) used as the base material for 70%+ of organic IC package substrates — the circuit boards inside BGA and CSP packages.
BT vs ABF substrates?
BT uses standard core-based construction for 2-12 layer substrates at 15-30um L/S. ABF is a build-up film enabling 2-5um L/S for advanced chiplet packages. BT is mainstream; ABF is advanced.
What line/space can BT achieve?
Production: 15-30um L/S with SAP/MSAP. Advanced: 10-15um with modified semi-additive. Below 10um typically requires ABF.
Is BT substrate the same as PCB?
Similar materials but different scale. BT substrates use 10-30um features, 50-100um vias, and clean-room processing — 3-10x finer than standard PCB fabrication.
Can AtlasPCB produce BT substrates?
We offer BT substrate fabrication for BGA and CSP packages, from 2-layer simple to 8-layer complex, with SAP fine-line capability to 15um L/S.
Need IC package substrate fabrication?
BT resin substrates — BGA, CSP, flip-chip — with SAP fine-line to 15um L/S. Prototype to production.
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