What is IPC-AJ-820? Background, Scope, and Application

The IPC-AJ-820 is a valuable resource for electronic assembly and its requirements. Developed by the Association Connecting Electronics Industries, it explains the science behind every step of the process, from material selection to production and rework. We delved into the document to give you a glimpse of its contents, chapter by chapter.

Key Takeaways

• What It Is: The IPC-AJ-820 is a guidance handbook, not a specifications standard.
• Release Year and Revisions: First edition in 1997, followed by a revised update released in 2012.
• Key Purpose: It explains the how and why of manufacturing electronic assemblies.
• Scope and Coverage: The handbook covers everything involved in producing electronic assemblies (handling, design, materials, assembly, coatings, cleanliness, and rework).
• Who Needs It?: Non-professionals seeking insight into electronic assembly, process engineers as a reference tool, and trainers looking for a knowledge base to use.  

What is IPC-AJ-820?

The IPC-AJ-820 is a technical manual developed by the Association Connecting Electronics Industries (IPC). Titled “Assembly and Joining Handbook,” it explains the “how” and “why” of manufacturing electronic assemblies.

The AJ-820 does not set quality requirements. Instead, it addresses the manufacturing process itself, acting as a guide for design considerations, material choices, and production steps, and offering best practices.

IPC-AJ-820 Background and Development

The IPC develops quality and manufacturing guidelines for the electronics industry. Manufacturers adopt the standards to ensure product quality and compliance with customer requirements or application needs.

The organization first released the IPC-AJ-820 in 1997. Later, advancements in electronics necessitated a revision, which came out in 2012. The update (Revision A) added new content to the original document.

It specifically included content for lead-free soldering and advanced IC packages with bottom terminations. It also included guidelines for identifying counterfeit components and for avoiding them.

In 2019, a Chinese version of the handbook was released. The translation was intended for the vast and rapidly expanding Chinese electronics industry.

IPC-AJ-820 Contents Chapter by Chapter

The AJ-820 covers crucial phases involved in the production of electronic assemblies. It presents the content in a 14-chapter manual. Each chapter tackles a specific topic, answering “how” and “why” questions and providing a comprehensive overview of the requirements.

Chapter 1 Introduction and Scope

The first chapter introduces the reader to the manual and provides a breakdown of its topics. It also helps the reader understand IPC-AJ-820, its purpose as a guidance tool, and how to use it with other IPC documents.

The chapter further defines key terms used in the document and explains the fundamentals of electronic assembly, distinguishing between through-hole and surface-mount technologies.

Chapter 2 Handling Electronic Assemblies

Electronic assemblies are prone to damage by electrostatic discharges, moisture, heat, and physical handling. This chapter focuses on their protection through proper handling and prevention strategies. It specifically addresses the following:

• ESD protection (grounding, work space requirements, handling practices).
• Moisture protection for sensitive components (baking, floor life management).
• Heat damage protection (process control and other techniques).
• Physical handling (practices that prevent contamination and damage during production, packaging, and storage).

Chapter 3 Design Considerations

The third chapter focuses on design strategies, offering crucial information for component selection and placement. In other words, it emphasizes the need for DFM (design for manufacturability). It covers these major topics:

• Design for automated assembly by using fiducial markings.
• Component orientation, accessibility, and clearance.
• Considerations for packaged components.
• Lead configuration and land patterns for through-hole and surface-mount assembly needs.

Chapter 4 Printed Circuit Boards

Here, the handbook explains how printed circuit boards can satisfy mechanical, thermal, and electrical requirements. It includes material selection, with special emphasis on laminates and coatings. The following topics are discussed extensively.

• Circuit board laminate materials and their qualities.
• Copper foil (types and thicknesses).
• Resins and plating methods.
• Surface finish types and characteristics (HASL, ENIG, OSP, immersion silver, immersion tin).
• Handling strategies.

Chapter 5 Electronic Circuit Components

This section examines the different types of components and their various requirements. It describes lead termination finishes, moisture sensitivity, integrated circuits, and detecting counterfeit parts. Here is a summary of what the chapter covers.

• Component types (THT vs. SMT, leaded vs. leadless, active vs. passive, discrete vs. integrated, electronic vs. mechanical).
• Lead termination finishes (tin, tin-lead, and palladium).
• Moisture sensitivity (moisture sensitive levels, baking, and handling guidelines).
• Bottom-termination components (BGAs and flip chips, relevant standards).
• Detecting counterfeit components (visual inspection, testing, sourcing, and supply chain control).

Chapter 6 Solderability

Chapter 6 provides insight into one of the most critical aspects of PCB assembly: the solderability of metal surfaces. It examines the causes of wetting problems and how to diagnose them, with reference to various IPC testing standards.

• Wetting mechanism.
• Solderability factors (surface finishes, contamination).
• Troubleshooting solderability problems (visual inspection and tests).
• Solderability Tests (IPC-J-STD-002 and IPC-J-STD-003 guidelines).

Chapter 7 Assembly and Joining Materials

This chapter is one of the most extensive. It covers assembly and joining materials, including solder alloy types, solder pastes, fluxes, and adhesives. The revised version includes Pb-free solder as one of the choices and explains its characteristics.

• Pre-soldering chemicals (solder mask, coatings, and fluxes).
• Choosing flux chemistries (organic vs. inorganic, clean vs. no-clean).
• Solder and solder paste alloys (Pb-based vs. Pb-free).
• Types of resin-based adhesives (silicone, epoxy, acrylic).
• Adhesive selection (conductive vs. non-conductive).

Chapter 8 Component Mounting

Component mounting is another fundamental process in PCB assembly. Chapter 8 provides placement guidelines for components, addressing alignment and orientation requirements, among other needs, as summarized below.

• Component mounting techniques (manual vs. automated).
• Placement technologies (through-hole, surface-mount, mixed).
• Mounting and placement guidelines (proper techniques and accuracy).
• Mechanical support hardware (heat sinks, spacers).

Chapter 9 Soldering Techniques and Connections

In this section, the reader learns about soldering technologies, namely wave, reflow, laser, and hand soldering. It provides a detailed analysis of the process steps, outlining critical considerations for each method, including quality. Here’s a brief look at what is covered.

• Wave soldering (flux application, pre-heating, and solder wave).
• Reflow soldering (the profiles, control parameters, and atmosphere requirements).
• Laser soldering (usage, control, and typical applications).
• Hand soldering (the soldering iron, how to choose, maintenance tips, and the soldering process).

Chapter 10 Joining and Assembly Methods

Here, the handbook introduces you to other assembly methods apart from soldering. These range from compression to using adhesives. The chapter also explains when these methods are applicable, such as when soldering is not possible or appropriate.

• Wire wrapping and bonding.
• Press-fit technology.
• Mechanical fasteners.
• Adhesive bonding.

Chapter 11 Cleaning and Cleanliness

The theme of this chapter is the cleanliness of electronic assemblies. The content takes the reader through cleanliness validation (whether to clean or not), cleaning methods and chemistries, the types of equipment, and how to test cleaned assemblies.

• Cleaning validation (visual inspection, contamination test).
• Clean vs. no-clean fluxes (whether to clean or not clean).
• Cleaning methods (aqueous, solvent, ultrasonic, vapor degreasing).
• Cleanliness tests (ionic contamination measurement, ion chromatography, ROSE test, SIR test).

Chapter 12 Conformal Coating

Electronic assemblies may require a protective layer (conformal coating) to shield them from environmental factors, such as moisture, or for insulation. Chapter 12 covers this requirement in detail. It explains the following.

• The function of coatings (environmental protection, insulation).
• Coating materials and their characteristics (silicone, acrylic, epoxy, urethane, parylene).
• Coating application methods (spraying, dipping, brushing).
• Curing techniques (air drying, heat, moisture, UV light).

Chapter 13 Potting and Encapsulation

Sometimes, potting and encapsulation provide better protection than conformal coating by making coatings thicker and more durable. This chapter explains how the two methods work and when to use them.  

• Potting and encapsulation materials.
• Consideration when choosing materials.
• Application and curing methods.
• Process control during application.
• Use cases (harsh operating environments).

Chapter 14 Rework and Repair

The last chapter explains post-assembly rework and repair steps. These are aimed at correcting assembly defects or introducing modifications. It also highlights the governing criteria for rework and repair processes.

• Determining factors.
• Limitations (e.g., maximum rework cycles).
• Rework methods.
• The rework process (removal and replacement of components, coatings, etc.).

Who Can Benefit from the IPC-AJ-820?

Anyone working in or with the electronics industry can benefit from IPC-AJ-820, whether they are professionals or not. They include designers, process engineers, assembly operators, quality control inspectors, and rework technicians.

Others are trainers (in-house or external) and businesses or individuals ordering electronic assemblies. The handbook is a valuable information resource that covers every aspect of manufacturing electronic assemblies.

Practical Applications of the IPC-AJ-820 Handbook

Although not a specification standard, the IPC-AJ-820 can help manufacturers achieve compliance. It provides guidance on materials, manufacturing processes, and best practices.

The document helps designers understand material and component choices. For process engineers and inspectors, it offers helpful insight into the how and whys of manufacturing steps, including the soldering process.

Training staff can also use it to impart knowledge to new or existing workers. They can be departmental trainers within an electronics manufacturing company or external and specialized in IPC certifications.

In addition to industry experts, customers and electronics enthusiasts can read the handbook to learn more about electronic assemblies and the technologies that build them. It provides comprehensive information that can help them understand the science behind these products

Conclusion

The IPC-AJ-820 is a comprehensive reference for the manufacture of electronic assemblies. While not mandatory, it provides helpful information for industry experts and anyone looking to know more about the assembly process.

Are you looking to understand PCB assembly beyond the basics? Venture Electronics provides in-depth guides and technical resources to support your quest for knowledge. Browse through our articles to learn more.

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