The Holzapfel Group, headquartered in Sinn near Herborn in the German state of Hesse, has been known as an innovative surface finisher for more than 75 years. It offers corrosion-protective, decorative, organic and functional process solutions for surface coating for almost all industries. With a new dynamic rotary tilting frame, the surface specialist ensures the efficient utilization of two important cleaning and production processes, but also fundamentally expands the possibilities for coating complex component geometries with this development. Just last year, the placement technology won first place in the "The Surface" competition at SurfaceTechnology.
The Holzapfel Group, which comprises four companies with a total of around 350 employees, develops process innovations and individual coating solutions. In addition to comprehensive contract services for coating components, the range of services also includes project planning, development and design services. To implement this holistic approach, the Group relies on strong, long-term partnerships with its customers and selected suppliers.
Nickel-plated high-performance heat sink in the installed state - Photo: stock.adobe.com/aicandy
Increasing demands on electroplating systems
The rapidly advancing development of electromobility and the increasing power density of increasingly compact electronic components are leading to ever-increasing demands on the components used. An undesirable but unavoidable by-product of this high performance is the process heat generated. In the past, it was often sufficient to dissipate this heat by means of air convection via cooling fins, but today it is often necessary to use closed liquid-carrying cooling systems. In addition, modern heat sinks for power electronics have to meet a variety of other requirements, which in their entirety go far beyond the simple dissipation of process heat.
In the past, it was often sufficient to simply "electroplate" components so that they shone, could be soldered or were protected against corrosion, but the tasks required of a modern job coater have changed significantly in recent decades.
The increasingly complex requirements placed on the overall product - the electroplated surface - are comprehensive. These include, for example
- ever tighter tolerances for the individual coating systems
- a steadily increasing number of measuring points on a single component and only a small permissible scatter over the total quantity of components produced simultaneously
- the demand for statistical process control (SPC) and the associated close monitoring and control of processes
- the fulfillment of even complex technical multiple requirements with a simultaneously high demand for a flawless visual appearance, even for purely technical components in the non-visible area
In many cases, the constantly increasing demands on the deposited surfaces correspond to those that can be achieved in small quantities with the effort and expense of manufacturing by appropriately trained specialists. However, high component quantities, strong international competitive pressure and fast and flexible response times require economically attractive and continuously reproducible solutions on a large industrial scale.
In order to meet these high requirements on an industrial scale for large series and at the same time ensure cost-effective production, it is therefore necessary for surface coaters to continuously develop their own processes.
In addition to the aforementioned problems, the following must also be taken into account
- rising energy prices
- rising costs for process chemicals
- rising costs for waste water treatment
- constantly increasing official requirements and regulations
- environmental protection
- CO2 footprint
- Shortage of skilled workers
- Rising personnel costs
Primary surface with 8µ nickel, secondary surface with 2µ nickel
Comparison of energy requirements per product carrier using the example of nickel deposition with Eta 98 %, 5.5 V bath voltage and a rectifier efficiency of 86 %Morethan electroplating: Pressure to innovate in process development
To be a modern, forward-looking and successful surface finishing company today, it is necessary to master more than just the originally primarily manual activity of electroplating. Industry 4.0, high volumes and international competition require economically scalable processes that do not lose sight of quality standards.
The recruitment and training of skilled workers, the (further) development of new methods and processes, the expansion of digitalization and the establishment and expansion of automation solutions are important building blocks for this.
It is necessary to initiate and accompany extensive projects and, as a competent partner, to support customers with our own expertise in the development of their products. From the idea to the finished product. After all, it is often only a few micrometers of surface area that ensure that the coated products function flawlessly for many years!
Technological solution: Variable rack technology
One specific example of a complex task is heat sinks made of copper with sophisticated geometries. Their rear side has a liquid-conducting structure that is surrounded on all sides by a rim several millimetres high, while the front side, on which the power electronics are soldered, is completely smooth and flat.
In addition to the scooping aspect, this geometry brings with it the problem that air bubbles can form depending on the component position - with uncleaned and uncoated areas along the entire process chain. In order to be able to manufacture economically, double-sided rack loading was also essential.
Another complicating factor was that the heat sinks are manufactured within a series using both cold and hot extrusion processes. Mechanical finishing is only carried out on partial surfaces. For the component surfaces, this means not only a visually differentiated appearance, but also differences in texture and oxide layer.
Solutions therefore had to be developed right from the pre-treatment stage to clean and prepare the surfaces on all sides in an efficient, economical and material-friendly manner - with the aim of achieving a uniform appearance and consistent quality for the subsequent coating process.
The Holzapfel Group developed the right solutions in collaboration with an efficient supplier network. As part of a joint development project with the Heilbronn-based rack construction specialist GS-Gestelltechnik, a unique PLC-controlled rotating and tilting rack was created - the heart of the HG-VRT (Variable Rack Technology).
This innovative technology was awarded first place in the Stuttgart Surface Technology Prize "The Surface" by Fraunhofer IPA at Surface Technology 2024.
The HG-VRT makes it possible to realize individual motion sequences depending on the process and position. Only with this key technology can the HG-USC (Ultra-Surface-Cleaning) and HG-PPT (Partial-Plating-Technology) processes developed by the Holzapfel Group be fully exploited.
Technological synergies
The possibility of process-specific component movement is not limited to the respective active process. The lifting and lowering processes can also be controlled individually for each process.
All processes, from the movement cycles to the tilting angle, are controlled and monitored in real time using a dedicated PLC and are fully digitally logged and archived. Material-friendly component handling and process reproducibility are ensured at all times.
Comparison of CO2 emissions generated for the electrolytic separation of nickel at 10,000 WT p.a. (380 grams CO2/kWh, Federal Environment Agency, as of 5.7.2024 for the energy mix in Germany)
Comparison of savings in drag-out losses in kg/p.a. using the example of a nickel electrolyte through variable component positioning during the extraction processVariety of applicationsfor variable rack technology
The application possibilities resulting from the technological innovations of the rotating and tilting rack technology, the variable rack technology, open up completely new finishing options for a large number of components. Almost every surface finishing company is regularly faced with the challenge of finding practicable and profitable solutions for increasingly complex components and coating system requirements.
Today's wide range of manufacturing and processing options enables the industry to produce increasingly complex geometric designs with multi-sided bores, in particular blind bores, surfaces that are scooped on all sides and extremely tight tolerances, while at the same time increasing demands are placed on the functionality, look and feel of the surface coating.
However, surface finishers are largely bound by physical and chemical conditions. Variable rack technology solves many of the aforementioned problems. The variable component positions in all processes make it possible to align the surfaces to be coated with the anode in a targeted manner. Whether this is done statically, in a continuous sequence of movements or with different, time-controlled movement patterns depends solely on the geometry of the component to be coated, its geometric characteristics and the requirements of the coating system to be produced.
Practical example: High-performance heat sinks made of copper
Liquid-carrying high-performance heat sinks made of copper, which are equipped with power electronics, place high demands on the coating: it must be absolutely pore-tight, even at low layer thicknesses, in order to prevent the release of copper ions and contact-corrosive reactions in the cooling circuit, which usually contains aluminum. At the same time, an even layer distribution is essential in order not to impair flow behavior and heat transfer - while at the same time ensuring that the opposite side can be soldered.
Classic static racks reach their limits here, especially for series with several million components per year. Highly scooping geometries also lead to air bubbles, uncoated areas and increased discharge of process fluids - with significant effects on quality, the environment and costs.
Additional challenges arise with multi-layer systems, as different electrolyte types require a reduced placement density or extended tolerances. Double-sided assembly is hardly economically feasible.
Variable rack technology addresses these problems in a targeted manner: it enables reliable, uniform coating of even complex geometries, increases cost-effectiveness, reduces environmental impact and significantly improves theCO2 footprint.
With the new rack technology, the technological balancing act of scaling manufacturing requirements to industrial standards while maintaining a high degree of flexibility has been achieved. The variable rack technology can be quickly and individually adapted to component-specific geometries and customer requirements.
Holistic approach to innovation
Innovative solutions such as variable rack technology represent an important and indispensable further development for the tasks of tomorrow. The development of ever more compact and technologically complex products and their individual components, combined with the ever more extensive requirements for surface finishing, makes it necessary to drive forward the further development of processes, procedures and technologies to the same extent. The Holzapfel Group is meeting these challenges with its Future Solutions. The Future Solutions division covers everything from prototype management for individual parts to the development of innovative system coating technologies for large-scale production. The Holzapfel Group also develops tailor-made component-related automation concepts and industrializes development projects.CO2-optimized solutions are also available on request. With the extensive know-how of its technical experts, the Holzapfel Group also offers comprehensive electroplating support as part of its Future Solutions.
More than just rack technology
Solutions such as variable rack technology offer much more than just the solution to a single problem. They combine the solution of a variety of technical problems and for a variety of components. Variable rack technology also makes it possible to conserve resources and actively contribute to environmental protection by reducing the carry-over of process fluids and improving theCO2 footprint.
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Advantages of the technology at a glance
The advantages of this technology can be used independently or in combination and generate different synergetic effects depending on the range of items:
- The variable rack technology makes it possible to double the output quantity per product carrier by equipping both sides of the rack without disruptive glare effects from the components on the front and rear of the rack.
- Robust and chemically resistant components and sophisticated mechanical functions reduce maintenance and servicing costs to a minimum.
- Interchangeable shelves ensure fast and cost-effective variability with multiple use of the variable rack technology.
- Touch contacts with triple redundancy per coating level ensure maximum reliability and process safety when transferring current to the components to be coated.
- Soft-drive for completely jerk-free motion sequences prevents damage, even to the most sensitive components made of soft base substrates.
- The variable rack technology makes it possible to reduce the drag-out losses of process chemicals by up to 78 % compared to a conventional static rack. This protects the environment through lower consumption of chemicals, lower salt loads in waste water and a significantly reduced amount of process water that needs to be treated.
- Depending on the component geometry and galvanic coating, partial plating technology enables a reduction of the active surface area by up to 52%* without upstream, intermediate or downstream mechanical masking and unmasking of the components. This makes it possible to save up to 65%** of the deposited metal as well as a proportional saving of energy*** for electrolytic deposition.
(* Percentage reduction of the component surface depending on the article geometry, **Percentage metal saving depending on article geometry, coating requirements and process ***Energetic saving depending on *, ** and cathodic efficiency of the electrolyte)
