Micro injection molded part

Recently, the telecommunication industry has undergone rapid expansion, and a strong consumer trend towards smaller and lighter telecommunication devices, such as cellular phones and notebook computers, is indicated. Small connection sockets and chip carriers are micro-injection-molded parts requiring the high flowability, high mechanical properties and dimensional stability of LCPs. These merits are now thought to be another application field for LCPs in the electronics industry. 

Micro injection molding parts, in other words, small parts with low weight (mass in mg) and the smallest dimensions and structures (Eigure 1.256). 

In either case, different tolerance, surface features, and accuracy may be required. Eor the micro injection molded parts themselves, the same rules apply (e.g., avoidance of sink points, etc.) as for normal plastic parts. Experience in micro-mold making and preliminary testing is mostly necessary. Here, the collaboration with the customer is a priority, much more so than in the area of standard shapes. 

Especially in micro injection molded parts, the question of further processing always arises. The smallest parts are often difficult and cost-intensive to further process. Through the use of multi-component injection molding, such assembly operations can be prevented. In this method, two or more different materials can be injected either simultaneously or sequentially and thereby create a composite part. 

Handling systems that combine several injection molding machines in micro or standard and micro injection combination. The micro injection molded parts are positioned precisely in the mold and placed in a precisely defined position. This circumstance can be used very well. Handling units remove and further transport the parts to testing, inspection, control, packaging, and assembly processes. 

Hot Runner Solution for Small and Micro Injection Molded Parts... 

Interesting hot runner solutions have been specifically developed for multi-cavity, gateless injection of smaii and micro injection molded parts in a confined space. As a standard system, solutions with 4, 8, and 16 injection points and injection intervais of only 8,10, or 20 mm are offered. Special gauges are available on request. The minimal installation dimensions of hot runner systems enable tbe use in molds with outer dimensions of 75 x 75 mm. Therefore, even with mold solutions for mini-injection molding machines such as babyplast, modular, multi-cavity hot runner direct connections can be realized. The outer dimensions of mini hot runner systems, illustrated in Figure 2.59, are only 34 x 32 x 100 mm. 

Micro-injection molded parts provide a large contact surface for aerial oxygen, so that surface degradation will be dominant. 

Compared to bulk materials, fiber-reinforced composites have already proven to exhibit superior properties in numerous applications. However, various desired combinations of properties, e.g., strong reinforcing effects at high optical transparency combined with electrical conductivity or reinforced micro-injection molded parts, cannot be achieved by traditional composites. The further improvement of the fracture toughness of resin matrices is another important task. Nanocomposites possess the potential to fill this existing gap. 

Mold Temperature Control on Micro Injection Molded Parts with Aspect Ratio Micro-features , 1275, ANTEC 2006... 

P. Deng, K. Liu, L. Zhang, H. Liu, T. Wang, J. Zhang, Micro and macro injection molded parts of isotactic polypropylene/polyethylene blends Shear-induced crystallization behaviors and morphological characteristics. J. Macromol. Sci. Part B Phys. 53, 24-39 (2014)... 

Hierarchical fibrillar model [80] This model was proposed for drawn TLCP fibers. They are composed of bundles of macro fibrils (5 p,m), fibrils (0.5 (Jim), and micro fibrils (0.05 p.m) in a hierarchical order (see Figure 8.17). This type of highly oriented fibrillar morphology is also found in the inner skin region of the injection-molded parts, as illustrated in Figure 8.18. 

In certain cases it will be necessary to provide for preliminary experiments. Programs for the computer-aided simulation of the micro-injection molding can be helpful in the early stages of part development and mold design. Under certain circumstances, such programs are overwhelmed by the size of the parts or structures. The programs available on the market should therefore be subjected to a detailed evaluation and testing phase. 

Compared to conventional molds, the size of the inserts and injection molded parts are the real challenge for the designer in micro mold making. The durability of the insert in the injection molding compound after removal from the mold and the subsequent use must be taken into consideration. This can be achieved by constructive measures with special geometric shapes, but also by surface treatments of the inserts. 

The micro injection molding process is similar to the conventional injection molding in terms of environment and continuing processes. The size of the parts has an additional influence on the MST process. Here are some examples ... 

In addition to continuing processes, the issue of cleanliness is also an important part of the environment. Clean rooms or clean room cabins are used or are mandatory in many fields of the micro injection molding technique. 

Micro injection molding differs from conventional injection molding in particular with respect to the surface/volume of the parts produced. Conventional injection molded parts with 2 mm wall thickness typically have a surface/volume ratio of 1 mm b Thin injection molded products such as compact discs may exhibit a 2 mm ratio. For micro components, typical surface/volume ratios range from 5 to 15 mm b... 

In this study, the dynamic mold surface temperature control is utihzed to achieve a rapid mold surface temperature variation to assist the injection molding of the LGP. When the mold temperature exceeds 140°C for the injection molded parts of the LGP, the dimensional accuracy of the micro-featirre achieved a rating of about 94.66% to 98.22%, so that reasonable accuracy in micro-feature replication can be achieved, residual stress can be reduced and litminance values can be increased by about 33.50% near the light soitrce and 49.40% farther from the hght. 

However, the microstructure of injection molded parts with micro-scale features is not fully understood. Microstructure of PC in the injection molded parts with micro-scale features characterized by Raman spectroscopy was discussed the relationship between microstructure and replication [5]. It has been clear that microstructure of the v-groove consists of multi layers, which are high molecular orientation layer and low molecular orientation layer. Molecular orientation of the surface layer close to the mold wall is higher than other area. 

For evaluating replication of the injection molded parts with micro-scale v-groove, the dimensions were measured using a non-contact 3-D laser measuring system Mitaka Kohki NH-3 and compared with dimensions of the mold cavity. The replication was defined as follows. Where... 

Figure 2. Micro tool manufactured by micro milling (above) and optical microscope image of an injection molded part (material polycarbonate).

Figure 7 shows that the micro-injection molded polyethylene parts exhibit typical skin-core morphology similar to that observed for conventional injection molding parts. While the interface between the skin layer and the transitional shear zone is apparent, the interface between the transitional shear zone and the spherulitic core is hard to locate. The skin layer probably has shish-kebab structural characteristics. The Kebabs , which are crystalline lamellae, fill the crystalhzed space. Fibrous crystals, or the Shishs , are ahgned parallel to the injection direction. They penetrate those lamellae. The fibrillar structure follows the direction of the flow, as shown in Figure 7. The transitional shear zone may be thought of as crystalline ribbons that branch and fill crystallized space with some loss of orientation. Crystallization occurring at the sites of both the skin layer and the transitional shear zone is significantly influenced by shear or elongational stress history. On the other hand, the influence of shear on the crystalhzation occurring in the spherulitic core is negligible. The crystalline structure...

All four processes have the abihty to replicate nano and micro sized features in a substrate material (see Table 1). Even though the features themselves may be at the nano scale, the substrate sizes and feature aspect ratios should be considered when selecting a process for replication. For example, hot embossing may be performed on substrates less than 0.5 mm thick, while injection molded parts generally need to have a thickness ofatleast2mm[ll]. 

Typical cycle times are 1-3 minutes for micro injection molding [1]. Gad aard et al. [12] state they were able to form their factor of 5 aspect ratio, nano scale parts with total cycle times betwem 30 and 45 seconds. In the cases where the micro features have low aspect ratios, micro injection molding can be much faster than hot... 

In micro-injection molding, similar to other manufacturing processes, one important objective is to obtain a consistent part quality. However, physically inspecting micro-parts is usually more difficult than inspecting conventionally molded parts primarily because of the difference in size[l]. Inspecting micro-parts requires extra attention because the defects are smaller and therefore more difficult to detect. To address this issue, a number of microscopic and surface evaluation... 

Processing window for micro-injection molding is smaller than in conventional injection molding process. Also, the time from polymer melt started filling the cavity to the part freezing happened in just a few seconds. Rapid freezing of polymer melts are easily noticeable among all the trials. 

---