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HDI Technology

HDI – HIGH DENSITY INTERCONNECT PCB
HDI boards, one of the fastest growing technologies in PCBs, are now available at Reada. HDI Boards contain blind and/or buried vias and often contain microvias of .006 or less in diameter. They have a higher circuitry density than traditional circuit boards.

There are 6 different types of HDI boards, through vias from surface to surface, with buried vias and through vias, two or more HDI layer with through vias, passive substrate with no electrical connection, coreless construction using layer pairs and alternate constructions of coreless constructions using layer pairs.

Key HDI Benefits
As consumer demands change, so must technology. By using HDI technology, designers now have the option to place more components on both sides of the raw PCB. Multiple via processes, including via in pad and blind via technology, allow designers more PCB real estate to place components that are smaller even closer together. Decreased component size and pitch allow for more I/O in smaller geometries. This means faster transmission of signals and a significant reduction in signal loss and crossing delays.

Via Fill Types
There are many different types of via fill material: non conductive epoxy, conductive epoxy, copper filled, silver filled and electrochemical plating. These all result in a via buried within a flat land that will completely solders as normal lands. Vias and microvias are drilled, blind or buried, filled then plated and hidden beneath SMT lands. Processing vias of this type requires special equipment and is time consuming. The multiple drill cycles and controlled depth drilling adds to process time.

Cost Effective HDI
While some consumer products shrink down in size, quality remains the most important factor for the consumer second to price. Using HDI technology during design, it is possible to reduce an 8 layer through-hole PCB to a 4 layer HDI microvia technology packed PCB. The wiring capabilities of a well-designed HDI 4 layer PCB can achieve the same or better functions as that of a standard 8 layer PCB.

Although the microvia process increases the cost of the HDI PCB, the proper design and reduction in layer count reduces cost in material square inches and layer count more significantly.

Building Non-Conventional HDI Boards
Successful manufacturing of HDI PCBs requires special equipment and processes such as laser drills, plugging, laser direct imaging and sequential lamination cycles. HDI boards have thinner lines, tighter spacing and tighter annular ring, and use thinner specialty materials. In order to successfully produce this type of board, it requires additional time and a significant investment in manufacturing processes and equipment.

Laser Drill Technology
Drilling the smallest of micro-vias allows for more technology on the board's surface. Using a beam of light 20 microns (1 Mil) in diameter, this high influence beam can cut through metal and glass creating the tiny via hole. New products exist such as uniform glass materials that are a low loss laminate and low dielectric constant. These materials have higher heat resistance for lead free assembly and allow for the smaller holes to be used.

LDI & Contact Imagery
Imaging finer lines than ever before and using semiconductor Class 100 Clean rooms to process these HDI parts is costly but necessary. Finer lines, spacing and annular ring requires much tighter controls. With use of finer lines, touch up rework or repair becomes an impossible task. Photo tool quality, laminate prep and imaging parameters are necessary for successful process. Using a clean room atmosphere decreases defects. Dry film resist is still the number one process for all technology boards.

Contact imaging is still widely used due to cost of laser direct imaging; however, LDI is a far better option for such fine lines and spacing. Currently most factories still use contact imaging in a SC100 room. As the demand expands, so does the need for laser drilling and laser direct imaging. All of Reada's HDI production facilities use the latest in technology equipment to produce this advanced PCB.

Products such as cameras, laptops, scanners and cell phones will continue to push technology to smaller and lighter requirements for the consumer's daily use. In 1992, the average cell phone weighed 220-250 grams and was strictly for making phone calls; we now call, text, surf the net, play our favorite songs or games and take pictures and videos on one tiny device weighing 151grams. Our changing culture will continue to drive HDI technology and Reada will be here to continue to support our customer needs.

  • HDI 1-N-1
  • HDI 1-1-N-1-1
  • HDI 1-1-1-N-1-1-1
  • HDI 1-1-N-1-1 micro via

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