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Case Study: Dual spindle technology- Should it be a trend?

Oct 13, 2011

How are drilling and routing machines and equipment manufacturing companies performing? What strategies do they employ? What is the value of dual spindle technology and is it a global trend? To answer the third question, first you'll have to keep on reading about this fascinating technology which is becoming more and more important in the US, as well as in Asia.

Drilling departments had sometimes been seen as a kind of "stable environment", but the drilling process turned out to be a real “bottle neck” for most circuit board production processes. Development of automation concepts and linear drives improved the performance of drilling departments in the past.

Dual spindle technology is based on the fact that two spindles drill simultaneously on the same panel. Today’s panels contain multiple images of the same circuit i.e. for cell phones, other mobile equipment, USB sticks, or substrates. In the case of substrates the number of individual circuits on a panel can run as high as several hundred. By drilling with two spindles at the same time the drilling time is divided by approximately two, therefore the productivity is doubled.

About 20 years ago, players in the industry started building up experience with dual spindle Technology. Some German PCB manufacturers started early to find new ways to increase productivity and grow their production capacity in the same or limited floor space. These days, they sought individual Swiss drilling machines with up to 80 spindles. But the spindle position could not be changed and tolerances worked out to be a real challenge. Over time, experience with equipment manufacturers had been built up and technology, machines and systems evolved.

For a long time it appeared as though laser technology would be able to replace traditional mechanical processing. Today both processes complement each other seamlessly. Mechanical circuit board processes have some advantages like easy adjustments or lower costs. Today with new drilling machines and new technologies like dual spindle technology, drilling productivity can still be heavily increased (up to 100%).

Beside productivity, the increasing board requirements are the second challenge for mechanical processing. With new designed circuit boards one has to deal with increasing complexity and smaller tolerances. That is why today’s dual spindle technology developments are concentrating on the issue of process accuracy.

The Swiss dual spindle machine tested below allows drilling with two independent X-axes (2 spindle drills at the same time) on the same station. It drills with an accuracy of  +/- 15.0 um. Up to now the greatest strength of a single drilling machine was the accuracy performance compared to dual spindle machines. Nevertheless, improved tolerances in the dual spindle technology allow for very thin circuit boards and structures to be processed with precision.

An extensive and detailed verification test can help to verify a dual spindle machine as a real and beneficial alternative. To share some valuable customer experiences with you, please find the summarized results of a performed test below.


Customer board test and dual spindle machine comparison

I would like to share with you an example of a Korean customer’s product test and evaluation project, with a machine from an equipment manufacturer in Europe's electronics supply chain and a well used Japanese drilling machine.

The Swiss drilling and routing machine which had been used for the comparison can be configured with 5-6 spindles, single or dual. It has full range linear spindles ranging from 200,000- 300,000 rpm. The X- and Y-axis run with 3150”min and  accelerates with up to 12.0 m/s2 which equals 1.22g. It enables an axis positioning accuracy of <+/- .4 mil” um, whereby the tolerances are continuously checked during processing. The Z-axis is capable of remarkably high rates of acceleration, up to 4.1g, enabling hit rates of up to 850 strokes per minutes. The motion system uses maintenance-free linear motors in all three axes. The linear motors allow for high process speeds, because very little mass needs to be accelerated and stopped.
The precise contact drill function (depth control accuracy of +- .6 mil”) offers an alternative to laser drilling. In addition, the Swiss dual spindle machine is equipped with an integrated new software revision, providing drill wear optimization and control system.

Positive effects of the new advanced software design are a shorter process cycle time and improved drilling and routing accuracy. It optimizes NC-part programs for dual spindle operation, improves distance and number of hits and targets even drill wear (on both spindles). Standard part programs can be used and the software manages the necessary changes. Preparation of the dual program does not need operator programming. The dynamic software 'balances' the tools and all tools are used 100%. The system can easily handle part programs with repeated images like mobile phones, HDI or substrates.
No repeat or step programming is needed and the program running time is very short. In addition, to better control tool yields, tolerances and maintain better transparency, an automatic accuracy check has been integrated. For best results, the reference holes are drilled with just one spindle to minimize measurement uncertainty. The check is done automatically after the production process and the operator is informed immediately and visually supported with the data’s to minimize maintenance. With this, spindle distance adjustments are merely done when needed and take only 5 to 10 minutes.
The software of the Asian machine does not combine it in one software tool. A second step and module needs to be run to achieve a new NC-program.

Within the Korean PCB manufacturer evaluation project, process capability cpk and productivity of the Asian single mode machine, had been compared with the Swiss machine. An average delta of -49% cycle time had been tested.

A significant reduction in process cycle time had been documented. The study shows a result of 148 minutes with the Swiss machine. This is approximately 70% less than the Japanese machine.

Environmental conditions of course, having an effect on production and test results and therefore the manufactures specs, should be used to re-produce highest quality. I will share some of the test and production conditions:

As is valid for all drilling processes, the room temperature must be stable. A maximum temperature fluctuation of ±1.8 °F should be the target. The absolute temperature can be between a min. temperature of +20 °C/+68 °F and a max. temperature of +25 °C/ + 77 °F.
The compressed air should be >7.5 bar at 1410 Nl/min. The cooling water used in the test had been <14°C, 60 l/min at 3.5 bar.
Vacuum with pressure -2'000 to -2'500 mmAQ, a flow of 25 Nm3/min and a floor with a flatness: < 4mm/m and min thickness of 500 mm (no antistatic covering).

Some insights on the R + D Management view

During my last discussions, Mr. Van der Klink  (R + D Technical Manager of the Swiss Equipment manufacturer) and I talked about the test results, conclusions, further strategies and projects.

Today, faced with the customer’s needs for productivity, better costs and capacity growth with less space, the company is working on some major initiatives.

First, they are pursuing what is called the "Product Design for Supply Chain." The initial goals were to reduce customer costs and drilling process time. During the last couple of years, machine productivity doubled and customer investment for the same spindle capacity (on a dual spindle machine) was reduced by 30%. This was achieved by the dual spindle product design (with more spindles on a machine) and through adjustment of the internal R + D processes. The philosophy always aimed at producing faster, cheaper machines and now it aims at more capabilities with equal and better performance, i.e., more spindles in the same floor space.

Secondly R+ D initative is "Design for Accuracy". On the Technology Roadmap and controlling matrix I have seen a current target and focus to get drill tolerances down to +/- 3.0 um (compared to single spindle machines) with the dual spindle technology. “This of course is an aggressive milestone but to achieve results, we want to close the gap with better single spindle machines. By achieving the goal, even denser and more complex products could be handled” Mr. Van der Klink  explained. This to me seems to be well connected to customer requirements and trends.

"We are working closely with our customers in our development projects" he said. "This combined with the fact that we spend approximately 15 % in R&D will ensure that we will maintain and further develop our technology leadership in the future. Our efforts are focused on generating higher speeds and the highest quality, providing the lowest maintenance and process costs for our customers."

In Conclusion

Dual spindle technology is ideal for drilling symmetrical patterns like substrates. Though, most PCB design processes focused on Supply Chain can be influenced to improve the productivity results even more. With an even number of columns on the board, productivity can be increased by exactly 100%. Some dual-spindle machines are suitable not only for drilling microvias but also for routing processes. Dual routing so far is just possible if the design includes an even number of columns, otherwise a manual routing step has to be added.

With a current average board mix, a dual spindle system reduces drill cycle time to a value between 60 to 100 % (depends on the program layout base) as compared with a machine (same type) in single mode.

The dual spindle technology supports a market with the need for productivity, process stability and the need for simply implemented capacity growth.

Key markets for the machines include: industrial design, telecommunications, as well as niche markets such as optoelectronic products, watches and hearing aids.

A dual spindle system uses half of the floor space of two standard machines. If drilling capacity needs to be increased in the same building/ department, a dual spindle system can add 100% more capacity without space consumption or investing in a new building. This too makes a dual-spindle machine much more cost effective from an investment point of view.

In terms of quality, the current machine capabilities are already delivering very good yields. However if a drill or operating problem occurs, it probably shows up on the doubled amount of spindles and boards.

Designed and built with high volume dense boards in mind on five to six station machines, and low volume lot sizes, as well as prototyping for one to three stations, dual spindle technology provides a cost and process effective solution for drilling and routing departments.

---- Foot notes ----

Machine 1 in the test had been a Posalux Ultra Speed G-line dual drilling and routing machine.
Posalux is a leading Swiss equipment manufacturer. The company builds high-tech drilling and routing machines for the PCB industry and special EDM and laser drilling machines for the machining of holes into nozzles for direct fuel or diesel injection for the automotive industry.

Machine 2 in the test had been a single drilling and routing machine of a major Asian manufacturer who offers drilling and routing machines for the PCB industry and is active in several other industries/ branches.

Volker Feyerabend is President of APROS Int. Consulting and Services ( He has a degree in Engineering and Economics. He has worked for Hewlett Packard, Agilent Technologies, Groz-Beckert in various international senior management positions. He also headed a European Outsourcing Organization with the focus on EMS/ PCB companies.

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