{"id":7892,"date":"2015-05-22T05:12:56","date_gmt":"2015-05-22T05:12:56","guid":{"rendered":"https:\/\/www.techdesignforums.com\/practice\/?p=7892"},"modified":"2015-05-26T10:59:41","modified_gmt":"2015-05-26T10:59:41","slug":"pcb-manufacturing-eight-steps-part-two","status":"publish","type":"post","link":"https:\/\/www.techdesignforums.com\/practice\/technique\/pcb-manufacturing-eight-steps-part-two\/","title":{"rendered":"Eight steps for efficient PCB manufacturing and assembly – Part Two"},"content":{"rendered":"

In the first part of this series<\/a>, we looked at the first four of the eight crucial steps that will help you achieve truly effective printed circuit board (PCB) manufacturing and assembly. Just to recap, those were:<\/p>\n

    \n
  1. Know your product<\/strong><\/li>\n
  2. Do only what needs to be done – and only when it needs to be done<\/strong><\/li>\n
  3. Be ready to make anything in any quantity at anytime<\/strong><\/li>\n
  4. Know exactly what you are doing at each stage in the process<\/strong><\/li>\n<\/ol>\n

    Now let\u2019s take a look at the remaining steps towards achieving success in PCB manufacturing and assembly. These are:<\/p>\n

      \n
    1. Stay on top of materials<\/strong><\/li>\n
    2. Develop efficient exception management<\/strong><\/li>\n
    3. Ensure assurance, conformance, and compliance<\/strong><\/li>\n
    4. Deploy seamless operational management<\/strong><\/li>\n<\/ol>\n

      As before, I’ll discuss each in turn, looking at technologies we can use to make them happen.<\/p>\n

      5. Stay on top of materials<\/h3>\n

      The price of holding excess stocks of raw materials in the factory can rival labor cost differentials in manufacturing in different locations across the world. Issues with PCB materials shortages have progressively shifted from the shopfloor to the warehouse. That does not mean they have been resolved, simply that they have been moved somewhere else.<\/p>\n

      Relatively frequent stock checks have become essential across the\u00a0entire\u00a0factory because significant discrepancies can accumulate between volumes recorded\u00a0in the ERP system and the physical volume of raw materials held on site. As a result, the minimum stock thresholds set for the warehouse by manufacturing resource planning (MRP) systems\u00a0are typically higher than necessary. The MRP managers want to ensure there are enough materials to cover any re-order\u00a0lead times in the additional context\u00a0of materials that may be ‘lost’\u00a0between physical stock checks.<\/p>\n

      Problems related to\u00a0material logistics have also spun out of control as raw material volumes have become unmanageable on the shopfloor. There are often\u00a0partially-used and improperly accounted material reels left around at the end of work-orders. Specific PCB management requirements\u00a0for materials used in surface mount technology (SMT) processes (e.g., progressive moisture contamination) are often compromised, leading to quality shortfalls.<\/p>\n

      As a result, customers’ requests for changes to delivery schedules are sometimes deemed impossible to meet\u00a0because of the high risks associated with the unknowns around physical material availabilities. Then,\u00a0there is the heavy workload involved in removing\u00a0and\/or reallocating kits of materials.<\/p>\n

      To regain some control, new tools uniquely identify all materials in the PCB assembly factory using barcodes. These are attached to each material carrier, be it a reel or something else. Each material has assigned attributes that inform\u00a0advanced stock management and tracking procedures, including support for SMT-specific issues such as the baking and dry storage of materials that are particularly sensitive to moisture. These software solutions enable lean materials management, including Kanban<\/em> control across\u00a0multiple warehouses and managed locations on the shop-floor, as well as the proper use and scheduling of just-in-time (JIT) deliveries.<\/p>\n

      Material selection from the warehouse is optimized for FIFO and many other configurable rules to reduce obsolescence, reduce search, improve location management efficiency, eliminate stock pick mistakes, and offer\u00a0specialist oversight\u00a0such as LED bin control. The correct stocks are verified in position on machines at setup to prevent those machines executing with a wrongly\u00a0located material. Accurate live materials consumption information is synchronized with ERP tools to adjust re-order quantities and ensure the integrity of the inventory.<\/p>\n

      This eliminates the need for periodic physical stock checks, minimizes machine setup errors, and reduces re-work and quality failures. It also cuts the volume of material stocked both on the shopfloor and in the warehouse while increasing productivity and making it easier to rework production schedules.<\/p>\n

      6. Develop efficient exception management<\/h3>\n

      Successful PCB manufacturing can be thought of as the creation, one after another, of perfect products. Variation that affects the quality of those finished products threatens that overarching goal.<\/p>\n

      The PCB\u00a0test-and-analysis regime has been developed to address defects that occur as a result of production processes gradually or suddenly going out of control. Let’s say, for example, that there is a change in the material supplier. Although the new company may be qualified to supply under a common internal part number, the switch can cause a sudden increase in placement errors if there is just a small difference in, perhaps, height. Machines’ visual detection algorithms can often detect\u00a0these problems, which is\u00a0good in terms of reducing placement errors but also results in an \u2018invisible\u2019 spoilage of materials at the machine.<\/p>\n

      Many other problems and defects\u00a0can slip through manufacturing, only to be discovered at test or even later in the market. Along with material-related issues, process issues around screen printing, SMT mounting accuracy, and reflow can all lead to\u00a0some degree of variation. The ideal scenario has the test process act as a filter, ensuring that no defective products make it out of the factory. However, the nature of PCB test means that this can never be guaranteed. Statistically, the greater the defect rate found inside the production operation, the greater the corresponding defect rate in the market.<\/p>\n

      A key factor in reducing defects through test and repair is the speed with which defects are detected and how quickly their prevalence across the factory is determined. Any delay between the defect occurring and being detected increases the likely number\u00a0of defective units. Several factors determine\u00a0the\u00a0time involved. They include:<\/p>\n