PCB Technical - LDI technology for mass production of HDI blind and buried via circuit boards

The advantage of LDI in these cases is that it can complete the precise alignment of the imaging on a large panel in one step without wasting time on multiple steps.

1. Output-The latest technological development of electronic products along with the improvement of laser power supply (from 4W to 8W) can now enable LDI to meet the high output requirements of HDI blind-buried circuit board production. The doubling of the laser power supply allows PCB manufacturers to obtain high imaging output while continuing to use their traditional dry film. Table 1 shows the comparison between the daily output obtained by a manufacturer using LDI with 8W laser (22-hour production) and the output obtained by using LDI with 4W laser from the same manufacturer. The energy settings are different (15 mj/cm2, 30 mj/cm2, 45 mj/ cm2, and 60 mj/cm2), the smallest body size is 50 μm.

The output improvement that can be achieved by using 8W laser is 50% to 80%, while using traditional dry ink, this is great for advanced HDI blind and buried via circuit boards with ring width less than 75 μm and precise alignment requirements. Improve. When using 15 mj/cm2 LDI dry film, LDI machine using 8W laser, the output can reach 3,500 prints/day, and at the same time, it can meet the high accuracy requirements of precise alignment. It is very surprising to see this. Table 2 compares the daily output of the 8W laser and the 4-step (used to achieve the required accuracy in the advanced HDI design) shutter exposure machine. The table shows that in some cases, for some very high accuracy requirements, an 8W laser LDI machine can exceed the daily output of a set of 2 shutter exposure machines! The output of the shutter exposure machine in Table 2 is calculated as [4 * (positioning time + exposure time) + operation time]. Positioning time=10 seconds, exposure time=3 seconds, operation time=6 seconds.

Automatic control-Obviously, automatic control is the basic requirement of any imaging method used in mass production and a necessary condition for achieving high throughput. For the requirements of automatic control, the requirements of each customer in various aspects are different.

*Automation concept―stand alone or inline, with flipper or without;

*Automatic control equipment suppliers-different PCB manufacturers want to cooperate with their respective automatic control equipment suppliers, and:

*Other specific requirements of customers-machine size restrictions, panel size, panel thickness and more.

In order to meet all the different requirements, automatic control interface solutions for LDI have been developed in the industry. Users all over the world have adopted different automatic control measures of the LDI machine. There are two main usage modes: Stand-alone automatic control equipment-automatic control equipment connected to a machine for picking and placing

Separated automatic control ―Automatic control equipment that connects two machines for picking and placing. One of the two machines is a plate turning machine, which forms an exposure unit with one side of the board, exposure in both machines, and one side of the board.

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2. Low-cost operation-Thest dual laser power supply (8W) technology not only enables higher output but also enables the use of low-sensitivity dry film. In fact, manufacturers can use their existing low-cost dry film. There is no need to replace the dry film with a faster and more expensive LDI dry film. Continue to use the dry film used in the current process while maintaining the same output. In some cases, it can even improve the output compared with other imaging methods such as shutter exposure machines. This is a good option for HDI blind buried vias. The LDI system used in mass production is a big breakthrough.

3. Compatible with existing processes --- Introducing LDI technology into mass production, manufacturers usually find it difficult and troublesome. The latest LDI technology solves some common problems for manufacturers who are considering introducing LDI into production:

"Do I have to replace the dry film I use now?" - The development of 8W laser technology in the 355 nm industry standard band enables suppliers to continue to use the existing dry film while achieving the required daily output .

"LDI's dynamic scaling function is very good for outer graphics, but will it cause more problems with the exposure of the solder mask?" ―In order to solve this requirement, several measures are used:

*Solder mask exposed by LDI-this is the ultimate solution to this problem. Major solder mask manufacturers, such as Sun Ink, Tamura, Huntsman, SUN Chemical, have developed fast LDI solder masks with a sensitivity range from 40 to 70 mj/cm2, especially for HDI applications.

*Different scaling modes-when the newly developed LDI group flux is not applicable, or when it takes time to verify the new group flux, the developed advanced LDI scaling mode allows the operator of the LDI machine to limit the dynamic scaling Scale the groups in segments, so that there are only a few groups of panels in each batch. In the later stage of the process, it is easy to generate a photographic plate (film) to expose each group, because it is known to use LDI to generate the scale factor of each group and it has been printed on the panel during the exposure of the outer layer pattern.

"For mass production, traceability tools are necessary. Can LDI support this requirement?" ―LDI's latest technology includes special tools to support mass production. The digital printing of LDI has special functions, and these functions are impossible to obtain using the photographic plate. The imaging method of each panel eliminates the need to cover all panels in a batch/batch with a "negative film", which gives LDI special personalized functions:

*Serial number imprint-this function can print a dynamic serial number for each PCB on each panel and or face to 134 pages and 132 pages.
*Date: This function can print the actual date of the printing plate.

*Scaling imprint: This function can print the actual scale factor of each board (X scale factor and Y scale factor), which is used for the production needs in the later process.
Summarize

As the alignment requireme

nts become stricter and more precise, it requires a replacement of the traditional exposure method. The latest developments in LDI technology, such as tasks, all requirements for mass production can be met through LDI, including accuracy, output, automatic control and traceability.