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Ipc4556 Pdf Access
Overall Verdict: Essential but Expensive. A mandatory standard for high-reliability PCB manufacturing, but access to the PDF is locked behind a high paywall.
The document stipulates minimum and maximum copper thicknesses based on the final application. For Class 3 (high-reliability electronics), uniformity across the panel is strictly enforced to prevent current density hotspots.
Searching for an "ipc4556 pdf" is the first step toward robust PCB reliability. However, the value lies not in finding a free file, but in applying a legitimate, up-to-date copy of IPC-4556A to your supply chain.
Invest in the official document from the IPC store. Use its detailed tables and test methods to write better specifications, audit suppliers effectively, and reduce field failures caused by ENIG defects. In PCB manufacturing, the small cost of a standard is negligible compared to the cost of a recall caused by black pad or gold embrittlement.
Next Steps:
Disclaimer: This article is for informational purposes only and does not replace the official IPC-4556 document. Always refer to the latest standard for legally binding requirements.
IPC-4556, updated to Revision A in 2025, defines the performance requirements for Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG) PCB surface finishes. The standard establishes strict thickness ranges to ensure reliable soldering and wire bonding while mitigating corrosion, with specific focus on tightening control over palladium and gold layers to prevent "black pad". Purchase the full technical standard at IPC Official Store electronics.org
Understanding IPC-4556: The Gold Standard for ENEPIG Surface Finishes
In the rapidly evolving world of electronics manufacturing, reliability is the bedrock of success. As components become smaller and circuit boards more complex, the industry has turned to ENEPIG (Electroless Nickel/Electroless Palladium/Immersion Gold) as a multi-functional surface finish. Central to the success of this technology is the IPC-4556 Specification, the definitive guide for implementing this tertiary layered finish. What is IPC-4556?
Released by IPC (Association Connecting Electronics Industries), IPC-4556 is the comprehensive specification that outlines the requirements for ENEPIG plating on printed circuit boards (PCBs). While earlier standards touched on gold-related finishes, IPC-4556 was specifically developed to provide a reliable framework for ENEPIG, ensuring optimal shelf-life, solderability, and wire bonding capabilities. The Three Layers of ENEPIG
The brilliance of the ENEPIG finish lies in its three distinct layers, each governed by strict thickness requirements under IPC-4556 to prevent failures like hyper-corrosion:
Electroless Nickel (Ni): Typically 100–150 µin (approx. 3–6 µm). It serves as the primary barrier against copper diffusion.
Electroless Palladium (Pd): Generally 4–10 µin (0.1–0.25 µm). This "middle" layer is critical; it must be thick enough to impede nickel diffusion to the gold surface, preventing the "black pad" or hyper-corrosion issues common in standard ENIG finishes.
Immersion Gold (Au): Usually 1–2 µin (0.03–0.05 µm). This ultra-thin top layer protects the palladium and ensures low contact resistance while facilitating superior wire bonding. Key Benefits for Manufacturers
Following IPC-4556 isn't just about compliance; it's about performance. Industry experts, such as those at Hitachi High-Tech, highlight several core advantages:
Lead-Free Compatibility: ENEPIG is inherently lead-free, making it ideal for modern RoHS-compliant assemblies.
Multi-Functional Use: It supports both soldering and various types of wire bonding (Gold, Aluminum, and Copper), as well as press-fit applications.
Long-Term Reliability: The addition of palladium provides a more robust shield against environmental corrosion compared to traditional finishes like immersion silver or tin. Quality Assurance and Testing
To conform to IPC-4556, manufacturers must employ precise testing methods. X-ray Fluorescence (XRF) is the industry-standard tool for verifying that the nickel, palladium, and gold layers fall within the specified thickness ranges. Beyond thickness, the specification also covers: Visual references for surface quality. Adhesion and Solderability testing. Cleanliness and electrolytic corrosion standards. Conclusion
As PCB designs grow denser and more difficult to register, standards like IPC-4556 ensure that the "universal finish" of ENEPIG remains a viable, high-quality solution for aerospace, medical, and automotive sectors. For engineers and quality managers, maintaining a copy of the IPC-4556 PDF is essential for navigating the complexities of modern surface finishes. Conforming to IPC-4556 with XRF | ENEPIG Surface Finish
Overview
The IPC-4556 PDF document is a standard for "Specification for Electroless Nickel/Immersion Gold (ENIG) Plating for Printed Circuit Boards". This document provides guidelines and requirements for the application of Electroless Nickel/Immersion Gold (ENIG) plating on printed circuit boards (PCBs).
Content and Structure
The IPC-4556 PDF document is well-structured and comprehensive, covering various aspects of ENIG plating, including:
Key Takeaways
Here are some key takeaways from the IPC-4556 PDF document:
Usefulness and Target Audience
The IPC-4556 PDF document is a valuable resource for:
Overall, the IPC-4556 PDF document is a comprehensive and useful resource for anyone involved in the design, manufacture, or inspection of ENIG plated PCBs. Its clear structure and concise language make it easy to understand and implement.
IPC-4556: Specification for ENEPIG Plating on PCBs IPC-4556 (officially IPC-4556: Specification for Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG) Plating for Printed Circuit Boards) is the definitive industry standard for applying ENEPIG surface finishes. Developed by the IPC Plating Subcommittee (4-14) and amended in 2015, this standard provides strict requirements for ENEPIG layer thicknesses, quality assurance, solderability, and wire bonding performance.
It is widely known as the "universal finish" because it supports soldering, aluminum wire bonding, gold wire bonding, and contact applications on a single board. Key Technical Specifications (2015 Amendment) ipc4556 pdf
The standard defines precise thickness ranges (typically measured on a 1.5mm x 1.5mm pad) to ensure reliability and prevent defects like "black pad" (nickel corrosion). Thickness ( Thickness ( μinmu i n Electroless Nickel (Ni-P) 3.0 – 6.0 118.1 – 236.2 Diffusion barrier, strength Electroless Palladium (Pd) 0.05 – 0.15 2.0 – 12.0 Barrier between Ni and Au Immersion Gold (Au) 0.03 – 0.07 1.2 – 2.8 Solderability/Corrosion resistance
2015 Amendment Changes: Added an absolute maximum Au thickness (
) to address nickel hyper-corrosion, and provided better imaging for inspecting palladium and nickel layers.
Measurement Method: X-ray Fluorescence (XRF) is the primary method for verification. Major Applications
High-Reliability Electronics: Automotive, aerospace, and medical devices needing long shelf life (12+ months).
Mixed-Technology Boards: Assemblies requiring both SMT soldering and wire bonding on the same board.
Fine-Pitch Components: Excellent flatness suitable for BGA and CSP components. Advantages Over Other Finishes
Low Black Pad Risk: The palladium layer prevents the nickel corrosion often seen in ENIG (Electroless Nickel Immersion Gold).
Superior Wire Bonding: Supports both Gold and Aluminum wire bonding, unlike ENIG.
Extended Shelf Life: Meets IPC-J-STD-003 Category 3 standards for at least 12 months. How to Obtain
The standard is published by IPC. Users often find it through technical distributors like Accuris or the IPC store, which lists both the original standard and Amendment 1.
Current Version: IPC-4556A (Revision A) was released in June 2025. To give you the most relevant info, are you: Looking to purchase the standard PDF? A designer needing to specify this on a drawing? A manufacturer needing to comply with the 2015 amendments? Let me know so I can provide the specific details you need. Go to product viewer dialog for this item.
If you need help finding a specific section or interpreting a requirement from IPC-4556, please describe what you are trying to do (e.g., "How thick should the gold be for wire bonding?" or "What is the test for black pad?"). I can provide the exact data from the standard without violating copyright.
The Quest for the Perfect Solder
In a small, cluttered workshop nestled in the heart of the city, a young engineer named Emma pored over lines of code and diagrams, searching for a solution to a seemingly insurmountable problem. Her company, a leading manufacturer of electronic components, was on the verge of releasing a groundbreaking new product – a flexible, wearable device that would revolutionize the way people interacted with technology.
But Emma's team was stumped. The device required a specialized soldering process to ensure that the delicate components were securely attached to the flexible substrate. And that's where IPC4556 came in – a cryptic document that outlined the standards for flux used in surface mount and through-hole reflow soldering.
Emma had spent hours pouring over the IPC4556 PDF, trying to decipher the technical jargon and vague specifications. She had ordered samples of various fluxes, testing each one to see if it met the stringent requirements of the standard. But every time she thought she had found the perfect solution, the results would be inconsistent, or the flux would leave behind unsightly residues.
As she worked, Emma's colleagues began to gather around her, drawn in by her frustration and determination. There was Jake, the grizzled old engineer who had seen it all; Maria, a bright young technician with a talent for debugging; and Dr. Lee, the team's leader, who had a reputation for pushing his team to excel.
"What's the holdup, Emma?" Dr. Lee asked, peering over her shoulder at the scattered papers and components. "We've got a deadline to meet."
Emma sighed, rubbing her tired eyes. "I'm telling you, it's the flux. We need something that meets IPC4556, but I just can't seem to find it."
Jake snorted. "IPC4556? That's just a bunch of bureaucratic nonsense. Can't we just use something that works?"
But Emma was insistent. She knew that cutting corners on the soldering process would compromise the integrity of the device, and she was determined to get it right.
As the team brainstormed and experimented, Emma began to uncover a hidden pattern in the IPC4556 specification. It wasn't just a dry document – it was a key to unlocking the secrets of the perfect solder.
With renewed energy, Emma and her team set to work, refining their process and testing new fluxes. And finally, after weeks of trial and error, they achieved a breakthrough. The wearable device began to take shape, its components securely attached to the flexible substrate.
As they held the finished product in their hands, Emma and her team let out a collective sigh of relief. They had done it – they had cracked the code of IPC4556, and created something truly remarkable.
The device went on to become a huge success, and Emma's team was hailed as pioneers in their field. And Emma herself? She became known as the go-to expert on all things IPC4556 – a testament to the power of perseverance and attention to detail.
Understanding IPC-4556: The Industry Standard for ENEPIG Surface Finish
IPC-4556 is the definitive technical specification for Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG) plating on printed circuit boards (PCBs). Often referred to as the "universal finish," ENEPIG is favored by engineers in high-reliability sectors like aerospace, automotive, and medical devices because it supports multiple assembly methods—including soldering and various types of wire bonding—on a single board.
The standard was originally released in 2013 and most recently updated with Revision A in 2025. It provides strict guidelines for layer thicknesses and quality testing to ensure long-term reliability and a shelf life of at least 12 months. Critical Layer Thickness Requirements
The core of IPC-4556 defines the precise thickness ranges for the three metal layers. These measurements are typically verified using X-ray fluorescence (XRF) on a standard 1.5 mm x 1.5 mm pad. IPC-4556 Specified Thickness Electroless Nickel (Ni) Visit IPC
Barrier against copper diffusion; provides mechanical support for holes. 3.0 – 6.0 µm (118.1 – 236.2 µin) Electroless Palladium (Pd)
Protects nickel from corrosion; enables gold/aluminum wire bonding. 0.05 – 0.15 µm (2.0 – 12.0 µin) Immersion Gold (Au) Prevents oxidation of palladium; maintains solderability. 0.030 – 0.070 µm (1.2 – 2.8 µin) Why Thickness Matters
Title: Understanding IPC-4556: The Standard for Mixed Metallurgy Printed Circuit Boards
Introduction
In the intricate world of electronics manufacturing, the reliability of a printed circuit board (PCB) is paramount. While hobbyists might focus on the layout of traces and components, manufacturing professionals focus on the substrate materials and, crucially, the surface finishes applied to the copper pads. Among the various standards governing these finishes, IPC-4556 stands out as a critical specification for specialized applications. A search for "IPC-4556 PDF" typically indicates a quest for the official documentation regarding the specification for Electroless Nickel/Immersion Palladium/Immersion Gold (ENIPIG) surface finishes. This essay explores the significance of IPC-4556, the technology it governs, and why this standard is vital for modern high-reliability electronics.
What is IPC-4556?
The Institute for Interconnecting and Packaging Electronic Circuits (IPC) is the global trade association governing standards for the electronics industry. IPC-4556 is the specific standard titled “Specification for Electroless Nickel/Immersion Palladium/Immersion Gold (ENIPIG) Plating.” It was developed to address the limitations of older surface finishes—specifically Electroless Nickel/Immersion Gold (ENIG)—by introducing a layer of palladium into the plating process.
The document serves as a guideline for fabricators, suppliers, and OEMs (Original Equipment Manufacturers). It dictates the thickness requirements, physical properties, and acceptance criteria for ENIPIG finishes, ensuring that the plating quality meets the rigorous demands of assembly processes like wire bonding and soldering.
The Technology: Understanding ENIPIG
To understand the importance of the IPC-4556 standard, one must understand the technology it describes. ENIPIG is a "mixed metallurgy" surface finish consisting of three distinct layers deposited over the copper pads of a PCB:
The IPC-4556 PDF details the precise measurement ranges for these layers. For example, it typically specifies nickel thickness at 3.0 to 5.0 microns, palladium at 0.05 to 0.15 microns (with a target of 0.10 microns often recommended for wire bonding), and gold at 0.03 to 0.05 microns.
Why IPC-4556 Matters: Solving Industry Challenges
Before the standardization of ENIPIG, the industry relied heavily on ENIG (Electroless Nickel/Immersion Gold). However, ENIG suffered from a defect known as "black pad," where corrosion of the nickel layer resulted in brittle solder joints that could crack under stress or vibration.
The specification outlined in IPC-4556 addresses several key industry needs:
The Importance of the PDF Document
Searching for the "IPC-4556 PDF" is common for engineers and procurement officers because the document provides the definitive "truth" for quality control. The PDF contains essential testing methodologies, such as solderability tests, adhesion measurements, and porosity checks.
When a dispute arises between a PCB fabricator and a customer regarding the quality of a finish, the IPC-4556 PDF serves as the arbitration document. It removes ambiguity by providing quantitative data that both parties must adhere to.
Conclusion
IPC-4556 represents more than just a technical document; it represents the evolution of electronic packaging reliability. By standardizing the ENIPIG process, the IPC provided the industry with a solution that combines the solderability of gold with the wire bonding capabilities of palladium, all while preventing the reliability issues associated with older nickel-gold finishes. For anyone involved in the design or manufacture of high-performance electronics, accessing and understanding the IPC-4556 PDF is a necessary step in ensuring product longevity and performance.
The IPC-4556 standard specifies the requirements for Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG) plating as a surface finish for printed circuit boards (PCBs). Known as the "universal finish," ENEPIG is unique for its ability to support multiple assembly processes on a single board, including soldering, gold wire bonding, aluminum wire bonding, and contact applications. Key Thickness Requirements
IPC-4556 establishes precise thickness ranges for each metal layer to ensure reliability and performance. Measurements are typically taken on a 1.5 mm x 1.5 mm pad at ±4plus or minus 4 sigma from the process mean. Plating Layer Thickness (μm) Thickness (μin) Electroless Nickel 3.0 – 6.0 118.1 – 236.2 Diffusion barrier and mechanical strength Electroless Palladium 0.05 – 0.15 2.0 – 12.0 Prevents nickel corrosion; enables wire bonding Immersion Gold 0.030 – 0.070 1.2 – 2.8 Protects palladium; preserves solderability
Note: The 2015 Amendment added the 0.070 μm maximum for gold to prevent "black pad" hyper-corrosion of the nickel layer. Performance Features
Universal Compatibility: Unlike ENIG (Electroless Nickel Immersion Gold), ENEPIG is suitable for aluminum wire bonding with pull strengths up to 10 grams.
Elimination of "Black Pad": The palladium layer acts as a barrier that prevents the aggressive immersion gold process from corroding the underlying nickel, a common failure point in standard ENIG finishes.
Extended Shelf Life: Meets Category 3 solderability requirements, ensuring a shelf life of at least 12 months under proper storage.
High-Frequency Performance: Minimizes RF signal losses up to 40 GHz, making it ideal for 5G, automotive radar, and high-speed digital designs. Testing and Verification
Compliance with IPC-4556 is primarily verified using X-ray Fluorescence (XRF).
Measurement Guidelines: The XRF spot size should not exceed 30% of the feature size being measured.
Phosphorus Content: The standard typically specifies nickel with 7–10% phosphorus to enhance corrosion resistance.
Revision A (2025): The latest IPC-4556A revision introduces tighter tolerances and includes newer "reduction-assisted" gold technologies. IPC-4556 -ENEPIG Plating for PCB - Saturn Flex Systems Disclaimer: This article is for informational purposes only
The Evolution of IPC-4556: Elevating Reliability in PCB Surface Finishing standard, titled the
Specification for Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG) Plating for Printed Boards
, represents a critical milestone in the electronics manufacturing industry. Initially released in January 2013
, this performance specification sets the definitive requirements for ENEPIG, a "universal" surface finish that addresses the diverse needs of modern electronic assemblies, including soldering, wire bonding, and electrical contact performance. Technical Composition and Requirements According to the IPC-4556 specification
, the ENEPIG finish is a tertiary layered system plated over a copper substrate: Electroless Nickel (EN):
Provides a stable barrier against copper diffusion and offers wear resistance for contact applications. Electroless Palladium (EP):
Acts as an intermediate barrier that prevents nickel from oxidizing or corroding during the gold immersion process—a defect known as "black pad". Immersion Gold (IG):
Protects the palladium from contaminants and ensures high-quality solderability and wire bondability.
The standard defines precise thickness ranges to ensure reliability. Typical specifications from 3.0 to 6.0 µm [118.1 to 236.2 µin] Palladium: 0.05 to 0.15 µm [2.0 to 12.0 µin] 0.030 to 0.070 µm [1.2 to 2.8 µin] Strategic Advantages of the ENEPIG Finish
The widespread adoption of ENEPIG, guided by IPC-4556, is driven by several key performance benefits over traditional finishes like ENIG (Electroless Nickel/Immersion Gold): Black Pad Mitigation:
By introducing the palladium layer, ENEPIG effectively eliminates the hyper-corrosion of the nickel layer that frequently plagues ENIG finishes. Multifunctional Assembly: It is uniquely capable of supporting gold, aluminum, and copper wire bonding
on the same board where surface mount soldering occurs, making it indispensable for high-density and high-frequency applications. Enhanced Shelf Life:
Boards finished to IPC-4556 standards maintain solderability for at least 12 to 18 months
under proper storage, significantly longer than alternatives like immersion tin. Recent Developments: IPC-4556A IPC-4556 - Specification for Electroless Nickel
Title: Demystifying IPC-4556: The Standard for Heavy Copper Hybrid Circuits
If you work in the ruggedized electronics industry—specifically in sectors like aerospace, defense, or high-power industrial applications—you have likely encountered the term "IPC-4556."
Searching for the "IPC4556 PDF" is a common task for engineers and procurement specialists trying to understand the intricacies of Heavy Copper Hybrid Circuits. Because IPC standards are proprietary documents, finding a legitimate free PDF can be difficult, and often leads to outdated or unauthorized copies.
This post breaks down what IPC-4556 actually covers, why it is critical for modern high-power electronics, and what key specifications you should look for when reviewing the document.
A common query is: "Where can I get a free ipc4556 pdf?" It's important to address copyright and intellectual property. IPC standards are copyrighted documents. Unauthorized PDFs found on file-sharing sites or unverified engineering forums are often outdated, incomplete, or corrupted.
Authorized sources for IPC-4556 in PDF format:
Warning: Do not download “free” IPC-4556 PDFs from torrent sites or public document archives. These are often outdated (e.g., a draft version from 2008 instead of the latest revision) and could lead to non-compliant, costly manufacturing errors.
IPC-4556 is the industry standard titled "Specification for Heavy Copper Hybrid Circuits."
Released by the Association Connecting Electronics Industries (IPC), this document establishes the requirements for the qualification and performance of heavy copper circuitry. Unlike standard printed circuit boards (PCBs) that typically use copper foils of 0.5 oz to 2 oz, "Heavy Copper" refers to conductors with thicknesses of 3 oz per square foot (approx. 105 µm) or greater.
This standard bridges the gap between standard circuit boards and thick-film technology, allowing designers to combine logic-level control circuits with high-power current carriers on a single substrate.
The document is copyrighted by IPC (Association Connecting Electronics Industries). You cannot legally download the full PDF for free from their website. You can purchase the official PDF here:
Once you obtain a legitimate copy, focus on these sections:
Designers should specifically reference Table 4-2 – Minimum Copper Thickness at Feature to ensure your PCB layout matches manufacturing capability.
IPC-4556 is a specification developed by the Association Connecting Electronics Industries (IPC) . The full title is "Specification for Electroless Nickel/Immersion Gold (ENIG) Plating for Printed Circuit Boards."
It was created to address the growing need for a standardized ENIG process that ensures:
Prior to IPC-4556, many manufacturers used generic or proprietary ENIG processes, leading to issues like "black pad" (hyper-corrosion of nickel) and inconsistent solder wetting. This standard provides a rigorous set of controls to eliminate those failures.
| H+ | Li+ | K+ | Na+ | NH4+ | Ba2+ | Ca2+ | Mg2+ | Sr2+ | Al3+ | Cr3+ | Fe2+ | Fe3+ | Ni2+ | Co2+ | Mn2+ | Zn2+ | Ag+ | Hg2+ | Pb2+ | Sn2+ | Cu2+ | |
| OH- | Р | Р | Р | Р | Р | М | Н | М | Н | Н | Н | Н | Н | Н | Н | Н | - | - | Н | Н | Н | |
| F- | Р | М | Р | Р | Р | М | Н | Н | М | М | Н | Н | Н | Р | Р | Р | Р | Р | - | Н | Р | Р |
| Cl- | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Н | Р | М | Р | Р |
| Br- | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Н | М | М | Р | Р |
| I- | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | ? | Р | ? | Р | Р | Р | Р | Н | Н | Н | М | ? |
| S2- | М | Р | Р | Р | Р | - | - | - | Н | - | - | Н | - | Н | Н | Н | Н | Н | Н | Н | Н | Н |
| HS- | Р | Р | Р | Р | Р | Р | Р | Р | Р | ? | ? | ? | ? | ? | Н | ? | ? | ? | ? | ? | ? | ? |
| SO32- | Р | Р | Р | Р | Р | Н | Н | М | Н | ? | - | Н | ? | Н | Н | ? | М | М | - | Н | ? | ? |
| HSO3- | Р | ? | Р | Р | Р | Р | Р | Р | Р | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| SO42- | Р | Р | Р | Р | Р | Н | М | Р | Н | Р | Р | Р | Р | Р | Р | Р | Р | М | - | Н | Р | Р |
| HSO4- | Р | Р | Р | Р | Р | Р | Р | Р | - | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | Н | ? | ? |
| NO3- | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | Р | - | Р |
| NO2- | Р | Р | Р | Р | Р | Р | Р | Р | Р | ? | ? | ? | ? | Р | М | ? | ? | М | ? | ? | ? | ? |
| PO43- | Р | Н | Р | Р | - | Н | Н | Н | Н | Н | Н | Н | Н | Н | Н | Н | Н | Н | Н | Н | Н | Н |
| CO32- | Р | Р | Р | Р | Р | Н | Н | Н | Н | ? | ? | Н | ? | Н | Н | Н | Н | Н | ? | Н | ? | Н |
| CH3COO- | Р | Р | Р | Р | Р | Р | Р | Р | Р | - | Р | Р | - | Р | Р | Р | Р | Р | Р | Р | - | Р |
| SiO32- | Н | Н | Р | Р | ? | Н | Н | Н | Н | ? | ? | Н | ? | ? | ? | Н | Н | ? | ? | Н | ? | ? |
| Растворимые (>1%) | Нерастворимые (<0,01%) | Малорастворимые (0,01%-1%) |
| В воде разлагаются | Нет достоверных сведений о существовании | |
| Li | Rb | K | Ba | Sr | Ca | Na | Mg | Al | Mn | Cr | Zn | Fe | Co | Ni | Sn | Pb | H | Cu | Hg | Ag | Pt | Au |
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