IPC-SM-784 vs Other IPC Standards: When You Need This COB Guideline

If you’ve ever worked on a chip-on-board (COB) project, you’ve probably stared at a list of IPC standards wondering which one actually applies to your assembly. I’ve been there. After years of designing COB assemblies for LED lighting and consumer electronics, I can tell you that IPC-SM-784 fills a very specific gap that no other IPC standard addresses.

In this guide, I’ll break down exactly what IPC-SM-784 covers, how it compares to related IPC standards like IPC-7351, IPC-A-610, and J-STD-001, and when you actually need to reference it for your COB projects.

What Is IPC-SM-784?

IPC-SM-784, officially titled “Guidelines for Chip-on-Board Technology Implementation,” is a 37-page document published by the Association Connecting Electronics Industries (IPC) in November 1990. It remains the primary industry guideline specifically addressing chip-on-board technology.

The standard provides comprehensive guidelines for:

• Design specifications for bare die attachment
• Manufacturing processes for COB assemblies
• Wire bonding techniques including gold and aluminum wire bonding
• TAB (Tape Automated Bonding) implementation
• Flip chip designs and attachment methods
• Thermal transfer considerations for heat dissipation
• Board selection criteria for COB substrates
• Testing guidelines and reliability requirements

Unlike broader assembly standards, IPC-SM-784 zeroes in on the unique challenges of mounting unpackaged semiconductor dies directly onto PCBs—something that through-hole and surface mount standards simply don’t cover.

Why IPC-SM-784 Matters for COB Projects

Chip-on-board technology eliminates individual semiconductor packaging, which creates both opportunities and challenges. You get smaller form factors, lower costs at volume, and reduced inductance for RF applications. But you also need specialized knowledge about die attachment, wire bonding parameters, and encapsulation that traditional SMT guidelines won’t give you.

The COB manufacturing process fundamentally differs from traditional SMT assembly. Instead of placing pre-packaged components, you’re working with bare semiconductor dies that require precise die attach adhesive application, accurate die placement, wire bonding under controlled conditions, and protective encapsulation. Each of these steps has specific process windows and quality requirements that IPC-SM-784 addresses.

From a business perspective, COB technology offers significant advantages. Eliminating individual device packaging can reduce component costs by 30-50% at high volumes. The smaller footprint enables more compact product designs—critical for wearables, IoT devices, and space-constrained applications. And for RF designs, the shorter interconnect lengths improve high-frequency performance by reducing parasitic inductance.

Here’s where IPC-SM-784 becomes essential:

Bare Die Handling: Unlike packaged ICs, bare dies are extremely fragile. The die surfaces are unprotected, bond pads are exposed, and any contamination can cause reliability failures. IPC-SM-784 provides specific guidance on die attach adhesives, curing profiles, and substrate preparation that you won’t find in IPC-7351 or IPC-A-610. The standard addresses proper die storage, handling ESD considerations, and inspection criteria before wire bonding.

Wire Bonding Parameters: The standard covers critical parameters for both ball bonding and wedge bonding, including bond pad geometries, wire loop heights, and pull test requirements. It addresses both gold wire bonding (the traditional choice) and aluminum wire bonding (lower cost for high-volume applications). The document provides guidance on bond pad pitch, bond pad metallization requirements, and the relationship between wire diameter and bond pad size.

Thermal Management: COB assemblies often handle significant power (think LED lighting). IPC-SM-784 addresses thermal substrate selection and heat dissipation methods specific to direct die attachment. The standard discusses thermal interface materials, the importance of void-free die attach, and how substrate selection affects overall thermal performance. For power applications, proper thermal management can mean the difference between a reliable product and field failures.

IPC-SM-784 Compared to Other IPC Standards

One of the most confusing aspects of IPC standards is understanding which ones overlap and which serve distinct purposes. Let me walk you through how IPC-SM-784 relates to the standards you’re probably already familiar with.

IPC-SM-784 vs IPC-7351: Design Guidelines Comparison

When to use which: If you’re designing a board with packaged surface mount components, IPC-7351 is your go-to for land pattern dimensions. If you’re mounting bare dies directly to the board with wire bonding or flip chip attachment, you need IPC-SM-784.

IPC-SM-784 vs IPC-A-610: Process vs Inspection

When to use which: IPC-SM-784 tells you how to implement COB technology correctly. IPC-A-610 helps your QC team determine if the finished assembly is acceptable. You’ll likely need both—IPC-SM-784 during design and manufacturing, IPC-A-610 during final inspection.

IPC-SM-784 vs J-STD-001: Complementary Standards

When to use which: J-STD-001 covers soldering processes for your board’s SMT and through-hole components. IPC-SM-784 covers the non-solder attachment methods used in COB (die attach adhesives, wire bonding, conductive epoxies). For a mixed assembly with both COB and SMT, you’ll reference both.

IPC-SM-784 vs IPC-SM-782: Historical Context

IPC-SM-782 was the predecessor to IPC-7351 and focused on surface mount land patterns. It’s now superseded, but you might still see it referenced in older documentation.

When You Need IPC-SM-784: Common Applications

Based on my experience, here are the situations where IPC-SM-784 becomes essential:

COB LED Lighting Assemblies

COB LEDs are everywhere now—high-bay industrial lighting, street lights, track lighting, and studio fixtures. These assemblies mount multiple LED dies directly onto aluminum-core PCBs for thermal management. IPC-SM-784’s guidance on thermal substrates and die attachment is directly applicable.

The LED industry has driven much of the recent growth in COB technology. A single COB LED module can contain 9 or more individual LED dies, all wire-bonded to a common substrate and covered with phosphor-loaded encapsulant. The thermal management requirements are demanding—LED efficiency drops significantly with temperature, and improper thermal design leads to accelerated lumen depreciation and color shift.

IPC-SM-784’s reliability testing requirements (thermal cycling from -55°C to +125°C) align well with LED qualification testing. Many LED manufacturers use IPC-SM-784 as their baseline, adding application-specific requirements for their particular products.

Consumer Electronics with COB Modules

Calculators, remote controls, and low-cost electronic toys often use COB to reduce costs. That black blob of epoxy you see on cheap PCBs? That’s a COB assembly, and IPC-SM-784 covers the encapsulation requirements.

The glob-top encapsulation process requires careful material selection and process control. The encapsulant must protect the wire bonds from mechanical damage and environmental contamination while maintaining acceptable thermal performance. IPC-SM-784 provides guidance on encapsulant properties, dispensing patterns, and cure requirements.

Automotive Sensor Modules

Many automotive sensors use COB for reliability and compactness. The standard’s reliability testing guidelines (thermal cycling, humidity testing, high-temperature storage) align with automotive qualification requirements.

Medical Devices

Implantable and portable medical devices benefit from COB’s size reduction. IPC-SM-784’s emphasis on reliability testing makes it relevant for Class 2 and Class 3 medical device assemblies.

RF and Microwave Applications

COB reduces parasitic inductance and capacitance compared to packaged ICs, making it ideal for RF applications. The standard addresses the specific substrate requirements for high-frequency performance.

Read more IPC Standards:

MIL-PRF-38534: Hybrid Microcircuits Military Specification Guide for Engineers

MIL-PRF-31032: The Definitive Guide to Military-Grade PCB Requirements

MIL-PRF-19500: Military Semiconductor Device Specification Explained

MIL-PRF-123: High-Reliability Ceramic Capacitor Military Standard

MIL-I-46058CMIL-I-46058C: Military Conformal Coating Specification Complete Guide

MIL-HDBK-263: ESD Control Handbook & Implementation Guide

J-STD-075 Guide: PSL Classification for Passive Components & Assembly Process Limits

J-STD-035 Guide: Acoustic Microscopy for IC Package Inspection & Defect Detection

J-STD-033 Guide: MSD Handling, Floor Life, Baking & Dry Storage Requirements

J-STD-032 Explained: Ball Grid Array Ball Construction & Performance Specs

J-STD-027 Guide: Mechanical Outline Standard for Flip Chip & CSP Packages

J-STD-020 Guide: MSL Classification, Reflow Profiles & Moisture Sensitivity Testing

IPC/WHMA-A-620 Explained: Complete Guide to Cable & Wire Harness Standards

IPC-SG-141: Complete Guide to S-Glass Fabric Specifications for PCB Laminates

IPC-QF-143: Complete Guide to Quartz Fabric Specifications for RF/Microwave PCB Laminates

Key Topics Covered in IPC-SM-784

Chip Types and Selection

The standard covers three primary die attachment methods:

1. Wire Bonding: Gold or aluminum wire connecting die pads to substrate traces
2. TAB (Tape Automated Bonding): Die attached via patterned tape carriers
3. Flip Chip: Bumped die attached face-down via solder or conductive adhesive

Each method has different requirements for substrate metallization, pad geometries, and process parameters.

Board Selection Criteria

IPC-SM-784 provides guidance on selecting appropriate substrates:

• FR-4: Standard choice for consumer applications
• Ceramic (Al₂O₃, AlN): High thermal conductivity for power applications
• Metal-core PCBs: Aluminum or copper core for LED and power electronics
• Flexible substrates: For flex-rigid COB assemblies

Wire Bonding Guidelines

The standard addresses critical wire bonding parameters:

• Bond pad dimensions and metallization requirements
• Wire materials (gold, aluminum, copper)
• Loop height and bond pull strength requirements
• Bonding tool selection and process windows

Thermal Management

For power COB applications, IPC-SM-784 covers:

• Thermal via design and placement
• Die attach material thermal conductivity
• Heat sink attachment methods
• Thermal interface materials

Reliability Testing Requirements

The standard references reliability tests including:

• Thermal cycling: -55°C to +125°C, 1000 cycles
• Humidity testing: 85°C/85% RH, 500-1000 hours
• High-temperature storage: 125°C, 500-1000 hours

How to Access IPC-SM-784

Official Purchase Options

IPC Membership Benefits

IPC members receive discounts on standards purchases. If your company regularly purchases IPC standards, membership often pays for itself.

Related Standards to Consider

When working with COB technology, you may also need:

• ASTM F219: Test methods for fine wire used in wire bonding
• ASTM F487: Specification for aluminum bonding wire
• IPC-FA-251: Assembly guidelines for flexible circuits (references IPC-SM-784)
• JEDEC standards: For semiconductor die specifications

Practical Tips for Using IPC-SM-784

After working with this standard for years, here’s my advice:

Start with the scope section: IPC-SM-784 clearly defines what it covers and what it doesn’t. This helps you understand when to reference other standards. The scope section establishes that this document focuses specifically on COB implementation—not general PCB design, not SMT assembly, not soldering processes. Understanding this boundary helps you build a complete standards framework for your project.

Cross-reference with your assembly house: Many contract manufacturers have internal procedures based on IPC-SM-784. Ask for their process specifications to ensure alignment. Good communication between design and manufacturing is critical for COB success. Wire bonding equipment capabilities, die attach material qualifications, and encapsulation processes vary between manufacturers.

Don’t ignore the reliability tests: The thermal cycling and humidity test parameters in IPC-SM-784 are less stringent than automotive (AEC-Q100) or space (MIL-STD) requirements. Know your end application’s requirements. For consumer electronics, IPC-SM-784’s test conditions may be adequate. For automotive or aerospace applications, you’ll need to define more stringent test conditions based on your application’s environmental profile.

Consider substrate limitations: IPC-SM-784 was written when FR-4 was the default. Modern applications often use metal-core PCBs or ceramic substrates that require additional considerations. The standard’s principles apply, but you may need to work with your substrate supplier to define specific requirements for surface finish, thermal conductivity, and bondability.

Document your deviations: If you deviate from IPC-SM-784 guidelines (and you probably will for specific applications), document why and what testing validated your approach. A well-documented deviation with supporting test data is far better than silently ignoring a standard requirement. This documentation becomes critical if you face customer audits or field failures.

Build relationships with your wire bonding equipment supplier: Wire bonding is often the most critical process in COB manufacturing. Your equipment supplier can provide guidance on optimizing bond parameters for your specific materials and configurations. They often have application engineers who can help troubleshoot bonding issues.

Frequently Asked Questions About IPC-SM-784

Is IPC-SM-784 still current despite being from 1990?

Yes, IPC-SM-784 remains the active standard for chip-on-board technology. While it hasn’t been revised since 1990, the fundamental principles of COB assembly—die attach, wire bonding, and encapsulation—haven’t changed dramatically. Many companies supplement it with internal specifications for newer technologies like copper wire bonding.

Can I use IPC-SM-784 for LED COB assemblies?

Absolutely. IPC-SM-784’s guidance on thermal management, die attachment, and reliability testing directly applies to LED COB assemblies. The thermal cycling and humidity test parameters in the standard are commonly used for LED reliability qualification.

What’s the difference between IPC-SM-784 and IPC-7351 for COB design?

IPC-SM-784 covers bare die attachment and wire bonding—the unique aspects of COB technology. IPC-7351 covers land patterns for packaged surface mount components. For a board with both COB modules and SMT components, you’d reference IPC-SM-784 for the COB area and IPC-7351 for the SMT land patterns.

Does IPC-SM-784 cover flip chip assembly?

Yes, IPC-SM-784 includes guidelines for flip chip designs, including bump requirements and attachment methods. However, for advanced flip chip technologies with fine-pitch bumps, you may need to supplement with more recent industry guidelines.

How does IPC-SM-784 relate to IPC-A-610 inspection?

IPC-SM-784 provides design and manufacturing guidelines. IPC-A-610 provides visual acceptance criteria for the finished assembly. Use IPC-SM-784 during design and process development, then IPC-A-610 during final inspection. IPC-A-610 includes some COB-specific acceptance criteria, but IPC-SM-784 provides the deeper technical guidance.

Conclusion: Choosing the Right IPC Standard for Your COB Project

IPC-SM-784 fills a specific niche in the IPC standards library. It’s not a replacement for IPC-7351 (land patterns), IPC-A-610 (inspection), or J-STD-001 (soldering). Instead, it addresses the unique requirements of chip-on-board technology that those standards don’t cover.

If you’re working on any project involving bare die attachment—whether it’s COB LEDs, automotive sensors, consumer electronics, or RF modules—IPC-SM-784 should be on your reference shelf. Combined with the appropriate inspection standards and your application-specific requirements, it provides the foundation for reliable COB assemblies.

For COB projects, I recommend this approach:

1. Design phase: Reference IPC-SM-784 for COB-specific guidelines and IPC-7351 for any SMT components
2. Manufacturing: Use IPC-SM-784 for COB process parameters and J-STD-001 for any soldering operations
3. Inspection: Apply IPC-A-610 acceptance criteria for the complete assembly
4. Reliability: Use IPC-SM-784’s test parameters as a baseline, modified for your application’s requirements

Understanding when to use IPC-SM-784 versus other IPC standards will save you time, reduce confusion with your manufacturing partners, and help ensure your COB assemblies meet the quality and reliability standards your application demands.

Useful Resources

Official IPC Standards Stores:

• IPC Official Store: shop.ipc.org
• ANSI Webstore: webstore.ansi.org
• GlobalSpec Standards Database: standards.globalspec.com

Related Standards Reference:

• IPC-7351B Land Pattern Calculator (free tool on IPC website)
• IPC-A-610J Acceptability of Electronic Assemblies
• J-STD-001J Requirements for Soldered Electrical and Electronic Assemblies

Technical Resources:

• IPC Knowledge Center: ipc.org
• IPC PCB Tools and Calculators (free resources)
• JEDEC Standards: jedec.org