{"id":2444,"date":"2025-09-08T08:51:05","date_gmt":"2025-09-08T08:51:05","guid":{"rendered":"https:\/\/flj-pcb.com\/?page_id=2444"},"modified":"2025-09-26T03:44:18","modified_gmt":"2025-09-26T03:44:18","slug":"resin-filled-via","status":"publish","type":"page","link":"https:\/\/flj-pcb.com\/vi\/pcb-manufacturer\/resin-filled-via\/","title":{"rendered":"L\u1ed7 th\u00f4ng qua \u0111\u01b0\u1ee3c l\u1ea5p \u0111\u1ea7y b\u1eb1ng nh\u1ef1a"},"content":{"rendered":"
\n\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t

Background<\/h2>

The resin-filled via process is used more and more in PCB making. It is common in boards with many layers and in high-precision PCBs. Resin filling can solve many problems that solder-mask plugging or lamination filler resins cannot solve. At the same time, the resins used in this process have special properties. Those properties bring many hard points in the board making steps.<\/p>

\"Resin-Filled<\/p>

Definition<\/h2>

Resin plugging means using resin to fill buried vias on inner layers, then doing lamination. This method is widely used in high-frequency boards and HDI boards. There are two main types: traditional screen-printed resin plugging and vacuum resin plugging. Most products use the traditional screen-print resin method. This is also the most common method in the industry.<\/p>

What is a \u201cplugged via\u201d on a PCB?<\/h2>

Via function and industry need<\/h3>

A via (plated through hole, PTH) connects different layers on a board. The growth of the electronics industry pushes PCB technology forward. It also raises the need for better board making and surface mount work. The plugged via process appears to meet these needs. Plugging must meet these rules:<\/p>

  1. The via must have copper inside. The via can be filled or not filled under the solder mask.<\/p><\/li>

  2. The via must have solder (tin-lead) inside with a certain thickness (for example 4 \u03bcm). Solder mask ink must not enter the hole and cause trapped solder beads.<\/p><\/li>

  3. The via must be covered by solder mask so that light cannot pass. The hole must not have solder rings or solder beads. The filled hole must be flat.<\/p><\/li><\/ol>

    As electronic products become lighter, thinner, shorter, and smaller, PCBs also move to high density and higher difficulty. This brings many SMT<\/a> v\u00e0 BGA<\/a> boards. When customers assemble parts, they often ask for plugged vias. Plugging serves five main purposes:<\/p>

    1. To stop solder from passing through the via during wave solder and shorting the part side. This is key when a via is placed on a BGA pad. Then plugging is done first, then gold plating, to make BGA soldering easier.<\/p><\/li>

    2. To avoid flux residue left inside the via.<\/p><\/li>

    3. To allow vacuum pick-and-place or vacuum test steps after surface mount and assembly. A sealed top is needed for vacuum to work.<\/p><\/li>

    4. To stop paste from flowing into the via and cause weak solder joints or poor placement.<\/p><\/li>

    5. To stop solder balls from popping out during wave solder and causing shorts.<\/p><\/li><\/ol>

      \"Cross-section<\/p>

      Advantages of Resin-Filled Vias<\/h2>

      1. On multi-layer boards with BGA, resin plugging can reduce the gap between vias. This helps routing and trace layout.<\/p><\/li>

      2. For buried vias in inner HDI layers, resin fill helps balance the thickness control of the prepreg during lamination and the resin fill design of the buried via.<\/p><\/li>

      3. For thick boards with large through holes, resin filling improves product reliability.<\/p><\/li>

      4. Resin-filled vias are often used because of BGA parts. In traditional BGA, a via may route from pad to the back side. If the BGA is dense and the via cannot route out, you can drill a via in the pad and route to another layer. Then you fill the hole with resin and plate copper to make it a pad. This is called the VIP process (via in pad). If you drill a via in the pad and do not use resin fill, solder may leak and cause a back-side short or a poor joint on the pad.<\/p><\/li><\/ol>

        Process Flow for Resin-Filled Vias<\/h2>

        General resin-filled via process:<\/p>

        1. Drill holes.<\/p><\/li>

        2. Plate through holes with copper.<\/p><\/li>

        3. Fill holes with resin and bake.<\/p><\/li>

        4. Grind or mill flat (planarize).<\/p><\/li><\/ol>

          After grinding, the resin part has no copper. Then a new copper plating step is needed to turn the filled area into a pad. This plating step is done before the normal drilling for other holes. In short, handle the vias that will be filled first, then drill other holes and follow the normal flow.<\/p>

          Below are some key steps and stations you may see in a factory:<\/p>