Focusing on fundamentals to drive world-class quality and throughput.

Most electronic products incorporate surface mount technology (SMT). Consequently, it is a critical process to monitor in terms of quality and cost. Lean manufacturing principles provide a solid foundation for eliminating the variation that can create defect opportunities as well as methodologies for improving throughput. Lean manufacturing-related philosophies in SigmaTron International’s facility in Tijuana, Mexico, include good manufacturing practices (GMPs), the single-minute exchange of die (SMED) methodology and total productive maintenance (TPM).

GMP in SMT: The basis of quality. GMPs are a set of guidelines that ensure products are manufactured and controlled consistently, following quality standards. In the context of SMT, GMP areas of focus include:

• Incoming control and component handling. Ensure that all components meet specifications before entering the line. This includes visual inspection, moisture verification (for moisture-sensitive components) and proper handling to avoid electrostatic discharge (ESD) damage.
• Inventory and warehousing management. Maintain strict control over component inventory, including FIFO rotation (first in, first out) and storage in controlled environmental conditions to prevent degradation of materials, especially solder paste and sensitive components.
• Regular cleaning and maintenance. SMT machines are precise and fast. Regular cleaning of nozzles, feeders, stencils and ovens, as well as preventive maintenance according to the manufacturer's specifications, is crucial to avoid defects and prolong equipment life.
• Staff training. Staff must be fully trained in equipment operation, soldering process, visual inspection and troubleshooting. A well-trained workforce reduces errors and improves process efficiency.
• Documentation and traceability. Maintain detailed records of component batches, process parameters (programs, libraries, load sheets and oven profiles), inspection results and any incidents or concerns that arise. This enables complete product traceability and facilitates immediate problem identification and correction.
• Solder paste control. Solder paste is a critical material. GMPs require controlled handling, storage, preparation and application to ensure shelf life and optimal solder properties for improved paste print quality.

SMED: Reducing model changeover times in SMT. SMED is a methodology developed by Shigeo Shingo to drastically reduce the time required to change a process from one product to another. In the SMT process, this translates into minimizing downtime between the production of different printed circuit board assemblies (PCBAs). The key principles of SMED for the SMT area are:

• Separate internal from external. Identify and move as many setup operations as possible outside of machine downtime (external operations). For example, set up feeders, stencils, squeegees, pallets and programs for the next model while the machine is still producing the current model.
• Turning internal into external. Look for ways to transform internal operations (which require the machine to stop) into external operations. This could involve using preset templates or interchangeable feeder carriages.
• Simplify internal operations. If an operation must be internal, simplify it as much as possible. This includes the use of quick-release fasteners, single-turn screws and standardized tools or fixtures.
• Organization and standardization. Have all the necessary resources, tools and components available and within reach. Standardize changeover procedures to make them repeatable and efficient.

Implementing SMED methodology in the SMT area reduces changeover times, enabling smaller batch sizes, greater flexibility in scheduling and planning, and a faster response to changes in demand.

TPM: Maximizing equipment availability. TPM is a comprehensive approach that seeks to maximize equipment efficiency throughout its lifecycle. It goes beyond traditional maintenance by involving all employees in the process and focusing on prevention. The pillars of TPM applicable to SMT include:

• Autonomous maintenance (Jishu Hozen). Empower and assist operators with clear, simple visual aids to perform basic maintenance tasks such as cleaning, lubrication and inspection. This increases equipment ownership and permits problem identification before it has a major impact.
• Planned maintenance (Keikaku Hozen). Develop a preventive maintenance program based on time, usage and equipment condition or characteristics. This includes scheduled inspections, parts replacement and calibration, if necessary.
• Quality maintenance (Hinshitsu Hozen). Focus on preventing equipment-related defects. This involves analyzing defect patterns and adjusting maintenance or processes to control or eliminate them.
• Early team management (Shoki Kanri). Incorporate lessons learned from maintenance into the design and selection of new equipment to ensure maintainability and reliability from the start.
• Education and training (Kyoiku Kunren). Continuously train operators and technicians in the skills necessary to operate and maintain equipment effectively and dynamically.
• Safety, health and environment (Anzen Eisei Kankyo). Ensure a safe and healthy working environment and comply with environmental regulations.

Adopting TPM in the SMT area helps reduce machine downtime, improve product quality and extend the lifespan of its most valuable assets.

The combined implementation of GMPs, the SMED methodology and TPM represents a powerful strategy for optimizing operations in the SMT area. It improves quality and reduces costs, and it increases flexibility, responsiveness and competitiveness in a constantly evolving market.

Oswaldo Arguelles is a process engineer in SigmaTron International’s (sigmatronintl.com) facility in Tijuana, Mexico.

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