Molded interconnect device

As Molded Interconnect Devices (English for: Molded interconnect devices ), short- MID electronic components are referred to, in which metallic conductors are applied to injection molded plastic support.

The main areas for the MID technique are the automotive, industrial automation, medical equipment, household appliances, telecommunications technology, measurement and analysis technology and the aerospace industry. The market volume of MID technology is subject to constant growth (market volume in 2004: € 10.7 million; 2005: € 14.1 million; forecasted volume for 2008: € 56.2 million ).

Benefits of MID technology

The advantages of the MID technology are both improved freedom of design, and environmental, as well as in a potential with respect to rationalization of the manufacturing process of the final product.

The improved design flexibility and the integration of electrical and mechanical functions in an injection molded part can lead to miniaturization of the module. In addition, new functions are implemented and any shape can be customized.

The rationalization potentials lie in reducing the number of parts ( material savings ) and the shortening of process chains. May further be increased by the reduction of assembly steps, the reliability.

By using the MID technique, the material mix a combination of PCB and mechanical component ( conventional approach ), which usually consists of many materials can be replaced by a metallized plastic part ( MID). MIDs are made of recyclable thermoplastics and are less susceptible to the disposal as conventional circuit boards. The base material for printed circuit board, however, is generally a difficult to dispose of and not recyclable thermoset.

MID production process

MIDs may be produced in various ways. The most important method for applying the interconnects as well as sending or shielding surfaces are the two-component injection molding, hot embossing, the mask exposure method, the laser structuring and film back injection. A distinction is made between subtractive and additive structuring metallizing process.

Two -component injection molding

One way is to produce the circuit carrier in the two-component injection molding. A plastic forms the main body, another is metallized and depicts the interconnect layout. From two- component injection molding, there is a large number of variants. The most common are the PCK and the SKW process.

When PCK method ( PCK = engl. (Printed Circuit Board Kollmorgen ) is used for the first shot a Metallizable, not electrically conductive plastic used. The conductor geometry of the MID is mapped sublime. During the second shot, the areas between the tracks with a are not metallizable plastic filled.

When SKW method ( SKW = engl. Sankyo Kasei Wiring Board) is injected, the conductor track structure as a depression of the non- metallizable component in the first shot. In the second shot, these areas are filled with the metallizable component.

After the second shot of the MID - based part in its final form and will be applied, the corresponding metals on the metallizable plastic in the subsequent steps. Here, the surface of the metallizable plastic is first activated. On this surface copper is applied to the desired thickness electroplated.

MID hot stamping

The hot embossing process is a fully additive manufacturing, which manages with very few steps. The injection-molded part, which has the final geometric shape already, is inserted into a stamping press. A surface-modified metal foil is punched simultaneously with the embossing tool, and bonded using pressure and heat to the molding. The stamping foils are provided with an adhesive layer or have a black oxide coating, which provides for the liability.

Hot stamping is characterized by the following points:

• Single-component
• Structuring by embossing
• A few steps
• Low investment costs
• Layout changes low
• Limited three-dimensionality

Laser MID method

In laser MID process, a distinction laser direct structuring (additive) and subtractive laser structuring:

Laser Direct Structuring ( LDS)

The LDS method uses a thermoplastic material, doped with a laser-active metal-plastic additive. The basic component is produced in single-component injection molding, almost without limits with respect to the 3D design freedom. A laser beam now writes the course of the conductors directly to the plastic. Where the laser beam strikes this plastic, the metal additive forms a micro-rough track. The metal particles that track form the nuclei for the subsequent metallization. In an electroless copper bath occur exactly on these tracks, the conductor layers. Succession can be so layers of copper, nickel and gold finish muster.

The LDS method is characterized by:

• Einkomponentenspritzguss
• There is a wide range of materials available
• Full three-dimensionality in a ball sphere
• Most flexibility: For a changed pattern of the traces only new tax data must be sent to the laser unit. This may arise from a base component different functional components
• Precision: Finest traces with a diameter of <80 microns are possible

The LDS process is patented by LPKF Laser & Electronics AG. Through a special paint with a LDS additive is any body can be structured. Thus, a component constructed in a 3D printer, and coated with the varnish LDS, the laser can be made such as in the injection molding Direktstukturierung component. The components are as create prototypes and can be used as a functional model or installation attempts. Thus, the LDS method closes the gap between the layout and series production.

Subtractive laser structuring

In the subtractive laser structuring the entire component surface is metallized and then applied etch resist. With the help of the laser, the etch resist is patterned and etched away the exposed copper layer.

Mask exposure method

After the injection molding of the plastic part and the surface activation is carried out first of all over the entire surface, a chemical base metallization with a thin copper layer. Thereafter, a photoresist is applied.

The exposing is carried out using a three-dimensional photo-mask and UV light. The exposed photoresist is developed and in the next step, the interconnect geometry is electrolytically reinforced the desired layer thickness. After application of an etch mask and removing the photoresist, the initially applied and no longer needed the copper is etched away.

The mask exposure method is characterized by the following points:

• Single-component
• Many process steps
• Fine wire widths possible
• Layout change cost possible

Film back injection

When a film insert molding, a multi-layer flexible printed image or sheet separately prepared is inserted into an injection molding tool and back-molded with suitable plastics.

The film insert molding is characterized by the following points:

• Single-component
• Structuring process prior to injection molding
• A few process steps
• Suitability for decorative surfaces

Flamecon ® process

Flamecon the method, a continuously supplied copper wire is melted and sprayed with compressed air to the supports. Major advantages are the chemical and maskless production, and the high degree of flexibility; it can be realized at low cost batch sizes of 1 through software-controlled robot. The method is developed by the Leoni AG and is designed to replace the manual cable harness production in a few years.

Research Association Molded Interconnect Devices 3- D MID eV

The Research Association Gung Molded Interconnect Devices 3 -D MID eV with 65 member companies and 18 research institutes of the largest industrial research association in the field of 3D-MID technology worldwide.

The Research Association was founded in 1993 in Erlangen. The aim of the research association is the promotion and development of MID technology. These projects are carried out to the community research, to promote exchange of experiences among the members and encouraged by appropriate publicity to implement the new technical possibilities. A particular concern is assisting small and medium-sized companies.