{"id":22790,"date":"2019-07-10T22:51:27","date_gmt":"2019-07-10T14:51:27","guid":{"rendered":"\/blog\/?p=22790"},"modified":"2023-12-01T14:38:10","modified_gmt":"2023-12-01T06:38:10","slug":"9-must-know-pcb-assembly-pcba-equipment","status":"publish","type":"post","link":"https:\/\/www.seeedstudio.com\/blog\/2019\/07\/10\/9-must-know-pcb-assembly-pcba-equipment\/","title":{"rendered":"9 Must-Know PCB Assembly (PCBA) Equipment"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n

When a large number of PCBs have to be made, chances are that components won\u2019t be manually soldered by hand. This is where professional assembly houses like Seeed will step in, to help fabricate both the bare boards and assemble all the parts onto the Printed Circuit Boards, or PCBs.<\/p>\n

But have you ever wondered how your manufacturers are able to stick that massive number of tiny components onto your PCBs? I have, but that was until I had to plow through paragraphs of technical jargon online about the machinery that gets the job done. While there\u2019 s nothing sexy about PCBA manufacturing, understanding how the brains of all electronics are made definitely brings joy and a sense of accomplishment. Lots of thought goes into each stage of the assembly process in order to deliver a perfectly functioning board. And with the electronics getting more and more advanced, machinery used to manufacture PCBs are ever-improving and more exciting than ever.<\/p>\n

In this blog post, we shall explore what goes behind the scenes in PCB assembly!<\/p>\n

In PCB assembly, there are 4 main stages of SMT, or Surface Mount Technology assembly using the reflow method, which are paste application, automated component placement, soldering,<\/strong> and inspection<\/strong> (plus testing, if requested). The basic equipment required for PCB assembly includes:<\/p>\n

    \n
  1. Solder Paste Printing machine<\/li>\n
  2. Solder Paste Inspection (SPI) machine<\/li>\n
  3. Glue Dispensing machine<\/li>\n
  4. Pick-and-Place machine<\/li>\n
  5. Reflow Soldering machine<\/li>\n
  6. Wave Soldering machine (for through-hole components)<\/li>\n
  7. Automatic Optical Inspection (AOI) machine<\/li>\n
  8. In-Circuit Test (ICT) Fixture<\/li>\n
  9. Functional Validation Test (FVT) Fixture<\/li>\n<\/ol>\n\n\n

    Stage 1: Paste Application<\/strong><\/h2>\n\n\n\n

    1. Solder Paste Printing Machine<\/h3>\n\n\n

    The first step in PCB assembly is the application of solder paste onto the board. Solder paste is a gray-colored goo made from a mixture of tiny particles of metal alloys; usually of tin, lead and silver. Think of it as a glue that will hold your completed board together. Without it, components wouldn\u2019t stick to your bare board.<\/p>\n

    <\/p>\n\n\n

    \"\"
    Solder paste (left), PCB stencil laser-cut holes (right)<\/em>
    (source: Chip Quik)<\/em><\/figcaption><\/figure>\n\n\n

    Before the paste is applied, a PCB stencil is placed over the board. A PCB stencil is a stainless-steel sheet that has small laser-cut holes that allow solder paste to be applied only to the areas of the board where the components contacts will eventually sit on the finished PCB, i.e. the SMD pads.<\/p>\n\n

    \n
    \"\"
    The solder paste printing machine in action<\/figcaption><\/figure><\/div>\n\n

    During the application of solder paste, the PCB stencil and the PCB are locked into place in the automated paste printer. A squeegee then applies lead-free solder paste on the pads in precise amounts. The machine then drags a blade across the stencil, to spread and deposit the paste evenly in the desired areas. After the stencil is removed, the solder paste will be exactly where we want it to be (hopefully).<\/p>\n\n\n

    2. Solder Paste Inspection (SPI) machine<\/h3>\n\n\n
    \n
    \"\"
    A Solder Paste Inspection machine<\/em>
    (Source: ce-exchange)<\/em><\/figcaption><\/figure><\/div>\n\n

    Numerous industry studies have pointed out that up to 70% of SMD soldering issues are traced back to improper or substandard solder paste printing. Hence, the next step is to check if the solder paste is printed properly onto the board. While employing good solder paste printing methods are often enough for PCBs in low volumes, SPI should be considered when churning out higher volumes of PCB to avoid high rework costs.<\/p>\n

    The SPI machine utilizes cameras capable of capturing 3D images, to evaluate the quality of the solder paste through factors such as solder volume, alignment, and height. The machine then rapidly identifies unsuitable solder volumes or imperfect alignment, allowing for manufacturers to quickly come down on bad solder paste printings and rectify the problem. When used together with Automated Optical Inspection (more on this later..), this enables manufacturers to effectively monitor and control the solder printing process, and therefore cut down on costs from rework and enable more efficient production of high-quality PCBs.<\/p>\n\n\n

    Stage 2: Automated Component Placement<\/strong><\/h2>\n\n\n\n

    3. Glue Dispensing machine<\/h3>\n\n\n
    \n
    \"\"
    A glue dispensing machine<\/em>
    (source: Fritsch)<\/em><\/figcaption><\/figure><\/div>\n\n

    Prior to component placement, the glue dispensing machine applies dots of glue onto the PCB where the body of the components will sit, to hold them in place until the leads and contacts are soldered. This is important for wave soldering where the force of the solder wave may dislodge larger components, or for double-sided wave or reflow soldering to stop components from dropping off.<\/p>\n\n\n

    4.<\/strong> Pick-and-Place machine<\/h3>\n\n\n\n
    \"\"<\/figure>\n\n\n

    The pick-and-place machine is probably the most mesmerizing machine in the whole assembly line. As its name suggests, the pick-and-place machine picks up components and places them onto a bare board. Traditionally, this stage of the PCB assembly process is done by hand, where a human would painstakingly pick and place components using a pair of tweezers. But fortunately, PCB manufacturers nowadays have this step automated using the pick and place machine, as machines are more accurate than humans and can work around the clock.<\/p>\n

    Pick-and-place machines suction up SMT components and place them accurately at their pre-programmed positions on top of the solder paste. They are thrown down at lightning speeds, with machines easily achieving speeds of 30,000 components per hour. As the machine places components in an organized but almost frantic manner, watching pick and place machines doing their job is certainly the most amusing to watch!<\/p>\n\n\n

    \"\"
    The little suction cups used to pick up components (left), and the automatic arm rapidly throwing parts down (right)<\/em>
    (Source: Essemtec, Youtube)<\/em><\/figcaption><\/figure>\n\n\n

    Also, we weren\u2019t exaggerating about the tininess of SMD components.<\/p>\n

    Here\u2019s a closeup of the opening where we feed components into the pick-and-place machine. Now, can you see where the SMD components are in this picture?<\/p>\n\n

    \n
    \"\"<\/figure><\/div>\n\n

    A little closer…<\/p>\n\n

    \n
    \"\"<\/figure><\/div>\n\n

    THERE THEY ARE.<\/p>\n\n

    \n
    \"\"<\/figure><\/div>\n\n

    Shown in the picture are small surface-mount resistors. In fact, there exists SMD components that are much smaller than this one. So, boy are we thankful for pick-and-place machines!<\/p>\n\n

    \n
    \"\"
    Tiny SMD resistors on the <\/em>Grove Infrared Temperature sensor<\/em><\/a><\/figcaption><\/figure><\/div>\n\n\n

    Stage 3: Soldering<\/strong><\/h2>\n\n\n\n

    5. Reflow Soldering machine<\/strong><\/h3>\n\n\n
    \n
    \"\"
    A Reflow Soldering Machine<\/figcaption><\/figure><\/div>\n\n

    Reflow soldering is the most widely used soldering technique for PCB assembly. Once the board is fully populated with components, the assembly is moved along a conveyor, through a long, giant oven called the reflow soldering machine. The PCB boards travel through various zones at carefully controlled temperatures, so that the solder paste melts and hardens steadily to form strong electrical connections between the components and their respective pads.<\/p>\n

    \"\"<\/a><\/p>\n

    The conveyor system drives the circuit board through each set temperature zone in the equipment, and the solder paste is dried, preheated, melted, wetted, and cooled, and the components are soldered to the printed board. The core part of reflow soldering is to use an external heat source to heat, so that the solder melts and flows and infiltrates again to complete the soldering process of the circuit board.<\/p>\n

    Reflow soldering has a series of advantages:<\/b><\/strong><\/p>\n