Press-in pin

The flexible type of press-in pin has become established on account of various technological advantages. Figure 5.5 compares the advantages and disadvantages specific to flexible and rigid press-in pins. 

The press-in pin (soiid orfiexibie) has a speciaiiy shaped zone (press-in zone) of a design suitabie for the estabiishment of a press-in connection. 

By means of a suitabie press-in tooi (machine), the press-in pin is pressed into the through-piated hoie in the printed-circuit board. 

A gas-tight connection must be made between the press-in zone of the press-in pin and the metaiiization of the hoie waii. 

FtGURE 5.5 Technological comparison of rigid and flexible press-in pins [48]... 

The requirements for the press-in zone of a press-in pin are high. The connection between the plated via and the press-in pin must be gas-tight, without the plated hole being subjected to excessive strain. A pin must also test to a certain holding force and must not exceed a maximum permissible volume resistance. Even an elastic press-in pin will undergo some degree of plastic deformation when pressed into a through-hole of small diameter close to the bottom limit of tolerance, so even elastic pins can be pressed in only once. In a sleeved hole, by contrast, a new pin can be inserted in the event of repair or replacement. [37]... 

Applied to the press-in connection technique, this means that the holding force of the press-in pin in the through-plated hole in the MID has to satisfy precisely defined minimum requirements in order to ensure sufficient security of the connector with regard to insertion, pull-out, and contact forces. The tolerances applicable to production of the interconnect device are stated in Fig. 5.16 reference to a 1.00 mm hole diameter. 

Another research project examined the reliability of press-in connections as a viable alternative connection technique for injection-molded interconnect devices. Unlike the project outlined above, in which the test program and selected methods were tailored to the object of examination, a test program set out in DIN EN 60352 Part 5 was definitive for qualification of the reliability of press-in pins. See Fig. 6.18. The test program is subdivided here into an assessment program for basic qualification of individual connections and an application program for checking connections that are part of a component/parent system. 

General check of press-in pins and interconnect device (> 220 specimens) ... 

FIGURE 6.18 Test program for ascertaining the reliability of press-in pins to DIN EN 60352 Part 5 (2001)... 

With regard to the components, vendors have methods of protecting them in transit from manufacture to installation. Vendors press the pins of ICs into antistatic foam to keep all the pins at the same potential. Also, circuit boards are shipped in antistatic bags, discussed earlier. However, keep in mind that unlike antistatic mats, antistatic bags do not drain the charges away, and they should never be used in place of an antistatic mat. 

Back-pressure regulators function by pressing a pin or a diaphragm into or over a relatively small hole. The gap between pin and hole is no more than a few tens of nanometers to hold 100-300-bar pressures at flow rates between 1 and 100 g/min of carbon dioxide/methanol. The expansion of the fluid down toward atmospheric pressure occurs in the hole just downstream of the pin or diaphragm. From 50 mL/min ( 45 g/min) at a density of 0.9 g/cm ), the fluid expands to up to 25,000 cm /min at atmospheric conditions. 

A sturdy barrel coupling or mounting ring is essential to proper operatioa This should be made to fit tightly around the barrel and threaded and screwed on or pressed and pinned in place. The designs shown here utilize threads to secure it However, many installations would be satisfactory pressed on and pinned. If the coupling hole is made... 

Screw feeders are used as independent units, or in combination, for many process operations. They are also used as integral components of equipment, such as roller presses and pin mills, and other powder processing machines. Their ubiquitous use is an essential feature of modern solids handling plant. Over this wide range of duties, users require a basic understanding of key performance-related features, in order to select equipment providing the best performance. 

Approximately one-fourth of all operating presses in the United States have a mechanical-type clutch (full revolution) which presents difficult and costly safety and maintenance repairs. If a mechanical clutch on a press is clicking while the flywheel or the bull gear is rotating, this indicates a potential problem. Immediate repairs should be made to safeguard the press operators. If not, the clutch pin may drop in, causing an unintended press cycle with possibly disastrous results. 

Charles Bernheimer, Decadent Subjects The Idea of Decadence in Art, Literature, Philosophy, and Culture in Pin-de-siecle Europe (Baltimore, Md. Johns Hopkins University Press, zooz), p. 109. 

Reitter, Paul. The Anti-Journalist Karl Kraus and Jewish Self-Fashioning in Pin-de-Siecle Europe. University of Chicago Press, 2008. 

Backplanes are special cases of multilayer PCBs.They tend to contain large qnantities of connectors that have been installed using press fit pins. In addition, backplanes are used to distribute large amounts of dc power to the system. This is accomplished by laminating several power planes inside the backplane and by bolting bus bars onto the outside surfaces. Some applications require that active components, such as surface-mount ICs, be soldered to their surfaces. This greatly increases the difficulty of assembly as a result of the need to solder fine-pitch parts to a large, thick PCB. 

The plated through-hole barrel is slightly deformed from the mechanical interference of the press-fit pin against it. The resultant forces from the collapsed press-fit lead against the PTH barrel waU result in stable, long-term mechanical and electrical contact. 

Instead, the press-fit pin is anchored solely by the mechanical interference between connector lead and the PTH barrel of the PWB. Oxides on the surface of the press-fit pin and mating PTH barrel are broken loose by the high frictional forces associated with the press-fit assembly operation, so nobility of materials, oxide build-ups, and material shelf-life are less critical considerations than in soldering. If conditions are proper in terms of sizing and materials, the press-fit process results in a gas-tight contact between the connector pin and the FTH barrel wall. 

Excessive plating on PTH barrel walls and annular pads (see Fig. 49.6c, d) can cause premature collapse of the compliant section of the press-fit pin. This condition may result in excessive pressing force to get the pin into the hole as well as insufficient normal contact force from the collapsed press-fit pin section to the barrel once fully seated in the hole. This condition poses an electrical contact reliability risk, as shown in Fig. 49.6e, where the pin is not actually in contact with the PTH barrel walls. 

Figure 49.7a shows a precoUapsed press-fit pin that is making only intermittent contact due to the PWB condition as depicted in Fig. 49.7b. 

FIGURE 49.7 (a) Excess nickel plate on a PTH annular ring has caused two problems. First, it has shaved material from the press-fit pin (arrows labeled x ). Additionally, it caused compression of the compliant section of the pin. When fully seated in the FIH, the pin was too loose for reUable contact The y labels demark a gap between the press-fit pin and the PTH wall. Compare this to (b), where pin shaving is evident but the pin is in intimate contact with the PTH barrel. (Scanning electron microscope (SEM) micrographs courtesy of A. Alexander, Jabil Circuits Penang, Malaysia.)... 

Use pressing equipment to remove or install press fit pins or link plates. Keep tooling in good condition and use it properly. If pressing equipment is not available, contact the chain manufacturer for additional guidance. 

If pressing equipment with appropriate tooling is available, mount the chain in a chain vise (Figure 14-4). Then press the pins out of one pin link plate (Figure 14-5). If pressing equipment is not available, the pins may be pressed out of the pin link plate with a pin extractor (Figure 14-6). The pin links removed from the chain normally are not reusable. 

If the chain is a riveted type, grind off the pin heads on one side of an outside link. If the chain has retainers or cotter pins, remove the retainers or cotters in one outside link. Not doing this can damage the chain bushings when the headed pins are pressed out. Support the top sidebar of the outside link. Then press the pins out of the top sidebar (Figure 14-16). 

Place a drilled anvil under the hole in the sidebar on the proper side of the chain. Carefully align the holes in both sidebars and the narrow end of the next link. Insert the pin by hand as far as it will go. Carefully align any flats or keys on the pin with the corresponding recesses in the sidebar holes. Press the pin into the holes of the sidebars (Figure 14-20). Then install the retainers into the connecting pin. Be sure that the joint flexes freely after the connection is finished. 

Many steel flat-top chains have the pin press fitted in one curl. Determine which end of the pin is in the press fit curl. Then press the pin out of the chain from the end with the press fit curl (Figure 14-21). 

To connect steel flat-top chain, find if the chain has a press fit curl. If so, press the straight pin into the chain from the end opposite the press fit curl (Figure 14-22). If all of the curls have the same size hole, the chain will need a shouldered connecting pin. In this case, press the pin into the chain with the smaller diameter leading (the same as for plastic chain as shown later). Be sure that the joint flexes freely after the connection is finished. 

Three-dimensional design freedom is restricted in the case of hot embossing. Vertical interconnects necessitate the use of additional processes. This entails inserting the film into preshaped holes in the substrate. Pins then press in enough conductive paste to fill the holes. 

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