Plated through-hole barrels

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. 

Press-fit assemblies are generally designed to accommodate at least two connector replacement cycles. The two cycles are predicated on (1) the normal force exerted by the press-pin s compliant section on the PWB s plated through-hole barrel wall, and (2) the quality and condition of the PWB s plated through-hole barrel surface after subsequent press-fit connector removals and replacements. 

Follow the press-fit connector manufacturer s recommendation for PTH finished hole size, tolerances, and acceptable or tested surface finishes. Use cross-section sample boards with high-aspect-ratio (depthidiameter) holes to quaUfy the PWB vendor and determine typical PTH barrel profile. Ensure that wall thickness of plated through-holes are uniform throughout their depth and meet connector specifications. Make certain that the surface finish on the PTH annular ring does not interfere with insertion of the comphant press-fit pin. 

Conductor configuration (Fig. 16) is a critical variable in susceptibility to CAF formation. The hole-to-hole configuration was the most susceptible to CAF as shown in Ref 4. This is due to the direct contact of the plated through-hole (PTH) barrel with the e-glass fibers (Ref 4). The track-to-track configuration was the least susceptible (Ref 4). The susceptibility of other configurations is between these two extremes. The data (Ref 8) confirmed these findings. An... 

Another issue to consider is the effects that solder alloys have on voids in plated through-hole (PTH) barrels. SnAgCu has shown to be more prone to voiding than tin/lead and SnCuNi alloys. If the leads are used for high-power resistance or temperature dissipation, this can be problematic. For many other applications, these voids will not cause... 

In accordance with the Invention, therefore, the chamber has at Its front end a section of reduced cross-sectional area. Weight, size and cost are reduced without seriously affecting the efficiency of noise reduction. The silencer may be built as an attachment or, preferably, the rear porfion of the chamber may be built around the barrel of the firearm, with communicating holes through the barrel. The heat absorbing material may be metal screen, which may take the form of apertured discs, stacked one upon another and preferably held In compression. Plating the screen with some metal such as tin before punching the discs will increase the stability of performance. ... 

I tested the fit of this piece in each of the two culverts my next trip out to the site and was satisfied with the result. At the same time, I solidified the anchoring scheme. While the dam plate anchors needed to be strong, I also wanted them easy to remove. I could satisfy both factors by attaching ordinary barrel bolts (for doors or gates) to the top of the dam plate on each side and sliding the bolt through holes drilled in the sides of the culverts. With the dam plates pushed down into one of the... 

I was ready to install the culvert dams. The outflow of the northern culvert was not easily accessible—it exits on a steep, unstable grade—so I first drilled a hole in the top of the culvert near the lip. Here, I used a %-inch bolt to secure a fitting to the top to which I was able to attaeh a elip of my tower-climbing belt. This safety harness enabled me to work hands free while installing the culvert dam. I tested the fit of the plate and drilled the holes for the barrel bolts in the eulvert s wall. With each culvert dam in place, I joined the diversion (culvert dam-to-barrel) pipes without glue to eaeh eulvert dam through the appropriate adapter. I then slid back the barrel bolts and tested the extent to which I could shift, lift, turn, or remove the culvert dam assemblies for periodic cleanout (or replacement) and safely re-install them. 

The breaker plate is a metal disk located perpendicular to the melt flow at the barrel exit. Containing several holes through which the melt passes, it is generally a little larger in diameter than the screw and mounts in a recession in the barrel exit flange. The breaker plate has three main purposes 1) to seal the end of the barrel, 2) to hold the screen pack, and 3) to straighten out the flow. 

The breaker plate is positioned between the output end of the barrel and the head of the extruder. It usually is made from one or two steel plates drilled with a number of holes. Screen-packs are placed between the two plates (or where there is only one plate, between the plate and the screw). The thickness of the plates and screens should be adequate to slow down or stop the helical movement of the material initiated by the rotation of the screw. The size of the breaker plate holes and the screenpack mesh must be optimized for optimum flow and pressure. Also the distance between the end of the screw and first plate or screw is important to eliminate irregular flow through the screenplate.and prevent excessive heating times. 

The extruded material exits the extruder through a die plate. The die plate is the final assembly located at the end of the barrel that contains drilled orifices or holes. The die plate has two major functions producing backpressure and shaping the product exiting the extruder. The extrudate is cut by an independent assembly... 

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