Rogers FR4 PCB Components Assembly High Volume Circuit Board SMT Assy

Product Specification

Rogers FR4 PCB Assembly Service High Volume Circuit Board SMT ASSY

Often encountered materials in PCB assembly service

• FR-2, phenolic paper or phenolic cotton paper, paper impregnated with a phenol formaldehyde resin. Common in consumer electronics with single-sided boards. Electrical properties inferior to FR-4. Poor arc resistance. Generally rated to 105 °C.
• FR-4, a woven fiberglass cloth impregnated with an epoxy resin. Low water absorption (up to about 0.15%), good insulation properties, good arc resistance. Very common. Several grades with somewhat different properties are available. Typically rated to 130 °C.
• Aluminum, or metal core board or insulated metal substrate (IMS), clad with thermally conductive thin dielectric - used for parts requiring significant cooling - power switches, LEDs. Consists of usually single, sometimes double layer thin circuit board based on e.g. FR-4, laminated on aluminum sheet metal, commonly 0.8, 1, 1.5, 2 or 3 mm thick. The thicker laminates sometimes also come with thicker copper metalization.
• Flexible substrates - can be a standalone copper-clad foil or can be laminated to a thin stiffener, e.g. 50-130 µm
  • Kapton or UPILEX, a polyimide foil. Used for flexible printed circuits, in this form common in small form-factor consumer electronics or for flexible interconnects. Resistant to high temperatures.
  • Pyralux, a polyimide-fluoropolymer composite foil. Copper layer can delaminate during soldering.

PCB Process - Introduction to HDI
HDI (High Density Interconnect): High-density interconnection technology, mainly using micro-blind / buried vias (blind / buried vias), a technology that makes PCB prototype service distribution density higher. The advantage is that it can greatly increase the usable area of ​​the PCB circuit board, making the product as miniaturized as possible in PCB assembly service. However, due to the increase in line distribution density, it is impossible to use traditional drilling methods to drill through holes, and some of the via holes must be drilled with laser drilling to form blind holes, or cooperate with inner-layer buried vias to interconnect.

Generally speaking, HDI circuit boards use the build-up method (Build Up), first do or press the inner layers, laser drilling and electroplating on the outer layer are completed, and then the outer layer is covered with an insulating layer (prepreg). ) and copper foil, and then repeat the outer layer circuit making, or continue to laser drill, and stack the layers outward one at a time.

Generally, the diameter of the laser drilling hole is designed to be 3 ~ 4 mil (about 0.076 ~ 0.1 mm), and the insulation thickness between each laser drilling layer is about 3 mil. Due to the use of laser drilling many times, the key to the quality of the HDI circuit board is the hole pattern after laser drilling and whether the hole can be evenly filled after the subsequent electroplating and filling.

The following are examples of HDI board types. The pink holes in the picture are blind holes, which are made by laser drilling, and the diameter is usually 3 to 4 mil; the yellow holes are buried holes, which are made by mechanical drilling, and the diameter is at least 6 mil (0.15 mm).

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