The Root Cause Analysis Process

What is Root Cause Analysis?

Root Cause Analysis (RCA) is a systematic process used to identify the underlying causes of defects, failures, or inefficiencies in manufacturing and business operations. Instead of merely addressing symptoms, RCA focuses on finding and eliminating the fundamental reason behind an issue to prevent it from recurring. It is widely used in electronics manufacturing, healthcare, engineering, and other industries where quality and reliability are critical.

The RCA process typically involves defining the problem, gathering data, and analyzing potential causes using structured techniques such as the 5 Whys Method, Fishbone (Ishikawa) Diagrams, and Failure Mode and Effects Analysis (FMEA). These tools help manufacturers trace issues back to their origin, whether they stem from supplier defects, process inefficiencies, equipment failures, or human errors. Historical data analysis and statistical methods are often used to validate findings and uncover trends that could indicate systemic issues.

By implementing root cause analysis processes, manufacturers can improve product quality, reduce costs, and enhance operational efficiency. It helps prevent defects from affecting production, minimizes waste, and ensures compliance with industry standards. Additionally, RCA strengthens supplier relationships by encouraging corrective and preventive actions that lead to better materials and components. 

How Root Cause Analysis Works

Root cause analysis is a systematic approach to identifying the underlying reason why a defect or failure occurred in a process or product. While organizations will tend to have highly customized processes to match their market needs and manufacturing processes, below is a basic example of an RCA process. 

Key Steps in RCA

1. Identify the Problem

• Define the issue clearly (e.g., “PCB failing functional test at power-up”).
• Gather data on when, where, and how the defect occurs.
• Quantify the impact (e.g., “10% of units exhibit this failure during final testing”).

2. Contain the Issue

• Isolate defective parts to prevent further production issues.
• Implement a temporary fix if necessary to continue production while RCA is conducted.

3. Investigate & Analyze Causes

Use a structured problem-solving technique to isolate the main cause of the issue (we have outlined three potential methods):

a) The 5 Whys Method

• Repeatedly ask “Why?” to trace back the issue to its root cause.
• Example:
  1. Why did the PCB fail power-up? → Capacitor failed.
  2. Why did the capacitor fail? → It was improperly rated.
  3. Why was it improperly rated? → Incorrect specification in the Bill of Materials (BOM).
  4. Why was the BOM incorrect? → Engineering design error.
  5. Why did the design error occur? → Lack of review process for new components.

b) Fishbone Diagram (Ishikawa Diagram)

• Organize potential causes into categories:
  • Materials (e.g., defective components)
  • Methods (e.g., incorrect assembly process)
  • Machines (e.g., soldering defects due to reflow oven issues)
  • Manpower (e.g., human error during inspection)
  • Environment (e.g., static discharge damaging sensitive ICs)

c) Fault Tree Analysis (FTA)

• Work backward from the failure, mapping out logical pathways that could have led to it.

4. Identify & Implement Corrective Actions

• Based on the root cause, apply Corrective Actions (to fix the current issue) and Preventive Actions (to stop recurrence).
• Example:
  • Corrective Action: Update the BOM to use correctly rated capacitors.
  • Preventive Action: Implement a design review checklist for component selection.

5. Verify Effectiveness

• Monitor production to ensure the issue does not return.
• Track defect rates before and after the fix.
• Conduct audits to ensure compliance with the new corrective actions.

The Value of Root Cause Analysis

Performing root cause analysis for incoming inventory and finished products provides manufacturers with several benefits that enhance product quality, reduce costs, and improve supply chain efficiency. By systematically identifying and addressing the underlying causes of defects or failures in received parts, companies can prevent recurring issues, leading to fewer production delays and rework. RCA helps maintain high product reliability by ensuring that only quality components enter the manufacturing process, reducing the risk of failures in the final product. Additionally, it strengthens supplier relationships by providing data-driven feedback, allowing vendors to improve their processes and maintain compliance with quality standards. Cost savings are another significant advantage, as RCA helps minimize material waste, warranty claims, and production downtime by proactively addressing defects before they impact assembly. 

RCA also contributes to continuous improvement efforts, helping manufacturers refine inspection procedures, enforce stricter quality controls, and implement preventive measures that enhance long-term operational efficiency. By leveraging historical RCA data, manufacturers can identify trends and make informed decisions about supplier selection, inventory management, and process improvements, ultimately leading to a more resilient and optimized supply chain.

Data Created from the RCA Process

When analyzing defects or failures in incoming parts or finished goods, manufacturers store various data points to track trends, improve supplier quality, and prevent future issues. Below is a breakdown of key data categories:

1. Basic Part Identification Data

• Part Number & Description (e.g., Resistor 10kΩ, IC Model XYZ123)
• Supplier Information (Name, Vendor Code, Location)
• Purchase Order (PO) Number (To track specific shipments)
• Batch/Lot Number (Essential for traceability and recalls)
• Date of Receipt (When the part was received in the facility)

2. Inspection & Testing Data

• Visual Inspection Results (Pass/Fail, defect descriptions, photos)
• Dimensional Measurements (For mechanical parts, connectors, or enclosures)
• Electrical Testing Data (Voltage, resistance, capacitance, signal integrity)
• Functional Testing Results (Does the part perform as expected in a circuit?)
• Automated Optical Inspection (AOI) Findings (Solder quality, component alignment)
• X-Ray & Microscopy Reports (For internal defects like solder voids or cracks)

3. Defect & Failure Data

• Defect Type & Description (E.g., cracked components, missing leads, incorrect labeling)
• Failure Rate (%) (How many defective parts per batch)
• Failure Mode Analysis (Open circuit, short circuit, out-of-spec values)
• Images of Defects (Captured via AOI, X-ray, or microscope)

4. Root Cause Analysis (RCA) Findings

• Root Cause Classification (Supplier issue, shipping damage, storage conditions, etc.)
• 5 Whys Analysis Summary (Why the defect occurred)
• Fishbone (Ishikawa) Diagram Data (Identifying contributing factors)
• Correlation Analysis Results (E.g., defect rate vs. humidity, supplier)
• Supplier Performance Trends (Comparing past RCA reports for recurring issues)

5. Corrective & Preventive Action (CAPA) Data

• Corrective Actions Implemented (E.g., supplier process change, internal handling adjustments)
• Preventive Actions Taken (E.g., stricter incoming inspection, supplier audits)
• Disposition Decision (Accept with deviation, reject, return to supplier)
• Supplier Corrective Action Request (SCAR) Response (If the supplier was asked to address the issue)
• Effectiveness Review (Tracking if defect rates improve after implementing corrective actions)

6. Traceability & Reporting Data

• RCA Report ID (Unique identifier for tracking past investigations)
• Responsible Teams (Who conducted the analysis—quality, engineering, supply chain)
• Time to Resolution (How long it took to identify and fix the issue)
• Historical Trends (Tracking defect rates over multiple shipments)

Managing Root Cause Analysis with the Right Software

As seen above, root cause analysis is a data intensive process. A purpose-built software system is the most effective way to manage the process and the data it creates because it streamlines data collection, analysis, and reporting, ensuring consistency and accuracy. Unlike manual or spreadsheet-based approaches, managing the RCA process through software centralizes all relevant information, including defect reports, inspection data, and corrective action plans, making it easier to track recurring issues and identify trends over time. 

Properly utilized software also standardizes RCA methodologies, ensuring that investigations follow best practices leading to more precise root cause identification and resolution. Standardized workflows within the software ensure that issues are assigned to the right personnel, deadlines are met, and follow-up actions are completed, preventing problems from being overlooked. 

Another key advantage of RCA software is its ability to integrate with other manufacturing systems, such as Material Requirements Planning (MRP) systems. This integration allows real-time data exchange, enabling automated defect tracking, supplier performance monitoring, and predictive analytics. With combined systems, manufacturers can visualize failure trends, correlate defects with specific variables (e.g., production shifts, supplier batches, or environmental conditions), and make data-driven decisions to improve quality control and reduce costs. Additionally, integrating RCA into greater manufacturing management software enhances collaboration across departments by providing a shared platform like Aligni’s DiscussAnywhere for engineers, quality control teams, and suppliers to document findings and corrective actions. 

By maintaining a digital record of all RCA investigations, companies can also demonstrate compliance with industry regulations and quality standards, such as ISO 9001, ensuring accountability and continuous improvement. Overall, a purpose-built RCA software system not only increases efficiency but also drives long-term quality and operational excellence.

Bringing It All Together

Ultimately, root cause analysis is a proactive, standardized approach that fosters continuous improvement, leading to a more reliable and optimized manufacturing process. The data intensive process does this by identifying the causes rather than the symptoms of part defects or failures. In order to efficiently operate RCA procedures, manufacturers need to have the right tools in place to collect and analyze the large amounts of data these processes create to uncover the insights needed to make appropriate changes.

Looking to learn the why’s of part and product failures? The first step is to get a software platform that can manage the data you need to find the ‘why.’ It’s time to sign up for Aligni MRP!