Patent Application
20170127580
The present principles relate generally to electronic devices and, more particularly, to electronic devices having a radiofrequency tuner shield on a printed circuit board.
The market preference for electronic devices such as set top boxes and the like (e.g. computers, game consoles, DVD players, CD players, etc.) is to have such devices be small, compact, and versatile. However, such preferences increasingly challenge the designers, because set top boxes and the like are required to perform more functions, which require the need for more internal components such as tuners and smart card assemblies in limited interior housing spaces.
Unfortunately, tuners and other components often require shielding within the interior of the housing to shield against radiofrequency interference and/or electrostatic discharge. The introduction of shielding essentially is an additional component which further complicates the designers of such electronic devices.
Additional considerations for designers is the fact that there is increasing pressure to make electronic devices at low cost and to make these devices in a manner that is rapid and easy to inspect.
To appropriately guard at-risk internal components, the common closed polygon vertical wall metal structures or shields have been employed, which are secured generally to a printed circuit board. These have been employed in the high volume manufacturing environments. Some electronic devices of particular interest have satellite receiver functions and include at least one F-connector requiring radiofrequency (RF) interference suppression. Because F-connectors tend to be larger than other components needing suppression or protection and F-connectors tend to have vertical height positions higher than the other components, RF interference suppression designs in devices with F-connectors has often been dictated by the F-connector. For example, one past design was a shield having a single height for the entire tuner shield that was dictated solely by the F-connector which was located at the back wall of the set top box and was located at a vertical position above the planar top surface of the horizontally oriented printed circuit board. Other past designs incorporated two separate tuner shields in which a first shield was a full height shield that covered the F-connector and a second shield had a lower height that covered other components. Another past design simply used a custom or specialized F-connector that had different spatial constraints, but is less preferred because of its higher cost.
With this background in mind, dual height shields for devices with conventional F-connectors have been recently favored over past designs. These dual height shields have thus been employed to accommodate the need to adequately shield higher and/or larger components and also shield adjacent lower and/or smaller components. These dual height shields provide shielding, reduce material use, and further aid in inspection, because the lower height regions of the shield make it easier to see components and connections. An example dual height shield design which is similar to the dual height shield described and used in the current principles is provided in the International Application PCT/US2014/067272 having an international filing date of Nov. 25, 2014.
A benefit of the dual height shield is that once the shield itself is installed, the structure makes it easier to repair or resolder the shield itself, the structure makes it easier to access and repair components within the perimeter of the shield, and the structure makes it easier to view the shield and components. The increase in solderability with such a design is facilitated by having regions with shallow walls. Additionally, the shallow walls make it easier for one to inspect the shield and components following thermal processing and/or other processing steps. Although dual height shields provide many benefits, dual height shields have also had issues. Some of the issues are associated with the nature of manufacturing variability that permits some degree of deviation from perfectly flat printed circuit board mounting surfaces and some degree of deviation from perfectly flat shielding bottoms and/or contact edges. Such deviates from absolute flatness makes it more difficult to solder a tuner shield to the printed circuit board over the entire length of the internal and external walls of the shield, thereby permitting gaps to form between the walls of the shield and the printed circuit board. These gaps can compromise circuit performances and often require a radiofrequency engineer to determine the critical areas that may need to be resoldered or otherwise may need additional attention. In mass production, such gaps have caused the need to design the shield with connection pins at specified regions along the shield contact edges at these critical points in which the pins engage and extend through corresponding mating plated-thru holes that are added to the printed circuit board. Solder paste will be applied only in these areas rather than the entire length of the wall. Due to the length of the pins being large enough to account for the expected variation between the tuner shield contact edges and the printed circuit board mounting surface, the pins which extend through the printed circuit board are guaranteed to provide solder connections in the critical areas. It should be noted that the lower height areas of the dual height shield can be more difficult to keep straight during shipping which can enhance variability.
Further, because of the difficulty of obtaining a large, perfectly flat tuner shield, especially along the bottom edges, and because of the difficulty of obtaining a large perfectly flat printed circuit board, it is difficult to get a tuner shield to solder to a printed circuit over the entire length of the internal and external walls of the shield. This has occurred even when it was deemed necessary to solder an entire wall edge. In other words, gaps between the printed circuit board surface and the shield edges appear to consistently exist that influence the quality of soldering.
At one point, it was thought that complete soldering around the entire peripheral walls would enhance shielding. However, attempts to completely solder the periphery were ineffective in mass production, because, as suggested above, not all gaps could be appropriately soldered to facilitate reliable shielding and some of these gap locations have been in areas critical to circuit performance causing the manufactured device to not operate properly.
The reality is that dual height shields have typically been applied to circuit boards by reflow-soldering which has required 100% inspection of the solder connections in the walls and often required the operators on the production line to rework or “touch-up” the solder connections. The “touch up” soldering is typically done with conventional soldering irons that tend to be large in comparison to the electronic components within the shields. This then would guarantee that the critical areas were soldered. Because of the large number of small surface-mounted components near the solder connections, such components are vulnerable to damage and, in fact, have been damaged during work.
One technique to improve soldering of shields to boards involved the implementation of solder pellets which provides an additional volume of solder in the critical area. The sizes of the pellets have been around the size of a chip component. The added solder was able to bridge moderate gaps between the shield and the board. Although this process worked well, the solder pellets add costs to the manufacturing process.
In the past, tuner shields had been added to boards after the reflow process and then the shields were later wave soldered. The tabs for the tuner shields would extend through the board and were then soldered when the printed circuit board ravels over a wave of solder. This process worked well assuming the tabs are in critical areas. The challenge, however, was this technique, as well as others that involved clearance holes in the printed circuit board, caused designers to make sure that bottom side components were kept laterally away from the shielded area and also caused the manufacturer to shield the bottom side components from the wave solder process. However, in recent designs, because of consumer demand for smaller devices, the sizes of the circuit boards must decrease resulting in the need for more of the circuit board area to be utilized. This makes it difficult to include some components in the devices such as smartcard connectors in the vicinity of the shield.
Hence, the current principles can include a shield design and process that avoids underside processing of the shield and permits underside components such as smartcard assemblies to overlap laterally with the shield.
In light of the above mentioned background, the current principles can provide an improved cost effective electronic device having a printed circuit board, electronic components requiring shielding, and a shield and to provide a method of manufacturing the improved electronic device that addresses the above mentioned drawbacks and disadvantages.
An electronic device in one embodiment of the present principles is disclosed that includes a vertical chassis wall having an aperture; a horizontal circuit board that extends toward the vertical chassis wall; an F-connector connected to the horizontal circuit board and extending out of the vertical chassis wall through the aperture; and an inner shield that can generally be used to contain or shield the radiofrequency circuit components mounted on the circuit board. The inner shield can comprise two parts: a proximal part near the F-connector that has a larger height and a distal part away from the F-connector that has a smaller height. The inner shield includes tabs that extend partially into solder plated clearance holes in the horizontal circuit board and are soldered into the clearance holes.
Another aspect of the present principles provides a method of manufacturing an electronic device such as a set top box or the like that includes providing a circuit board that supports electronic components on a first or top surface and providing a tuner or radiofrequency shield that will surround the electronic components, wherein the tuner shield can be the dual height shield. The method can include determining locations on the surface of the circuit board and corresponding locations along a bottom or contact edge of the shield that correspondingly serve as holes in the circuit board and pins or mating extensions of the shield, wherein the locations are positions that are critical regions for shielding the electronic components from radiofrequency interference. Further, the feet can be formed to extend at least partially through the circuit board and wherein the holes can be plated in preparation for soldering in which the soldering can occur in reflow oven. The method can include forming the radiofrequency shield to have a higher height shield region that forms at least one higher height shield room and a lower height shield region that forms a lower height shield room. The method can include forming the radiofrequency shield to have shield rooms and attaching portions of less than 100% of straight interior vertical walls of the shield rooms to the printed circuit board by reflow-soldering.
The present principles may be better understood in accordance with the following exemplary figures, in which:
The invention will now be described in greater detail in which embodiments of the present principles are illustrated in the accompanying drawings.
An advantage of this shield design is that the lower height region 317 makes it easier to repair, optically inspect and troubleshoot the shield 312 and the components contained within the shield 312 after the shield is affixed. Further, this lower height region 317 makes it easier to finish and/or complete the manufacture of the electronic device 1. The lower height region 317 allows for easier soldering and inspecting of the components within the shield and the shield 312 itself, wherein the ease of soldering is enhanced, because the lower height region 317 can have relatively shallow walls. The shallow walls make it easier to see inside the walls of the shield 317 at various stages of manufacturing and after some of these stages, which include thermal processing stages, that can often cause components to move and/or change in some respects. It should be noted that the positioning of the solder pins or feet 502 depends on the requirements of the electronic device and the components therein. Thus, the number and position of the solder pins or feet 502 and corresponding contact points 520 in the printed circuit board 501 can depend and/or be dictated by the wavelengths of the applicable radiofrequency waves.
The shield 312 can be a unitary structure of one folded metal sheet with designed bends and joints, which can be analogous to Origami art in which the solder pins or feet 502 can be formed with the metal sheet. Folded corners 319 can be present and can increase stability. The folded corners 319 include adjacent vertical wall portions and can include a horizontal wall portion 319H extending from the vertical wall portions.
The shield 312 in
The shield back wall 318 can be parallel to and adjacent to the vertical chassis rear wall 3, the shield front wall 320 can be opposite the shield back wall 318, and at least two outside vertical side wall portions 321 can extend from the shield back wall 318 to the shield front wall 320. The shield walls can be linear or can have bends. The shield back wall, shield front wall, and outside vertical side wall portions comprise the series of vertical peripheral walls. The proximal portion 316 of the vertical peripheral wall is the back wall 318 and the portions of the outside vertical side wall portions connected to the back wall 318 in proximity of the back wall. The proximal portion 316 of the shield near or toward the back wall 318 has a larger height than the distal portion 317 of the vertical peripheral wall near or toward the front wall 320. The outside vertical side wall portions 321 can have an intermediate region 315 in which the proximal portion transitions to the distal portion. In this intermediate region 315, the height of the peripheral wall reduces from a larger height to a lower height.
Referring to
The electronic device can further include a top or shield cover 311 for the shield 312 in which the top or shield cover includes at least three portions: a proximate cover portion 330 that covers the proximal portion or the higher height region 316 of the vertical peripheral walls, a distal cover portion 331 that covers the distal portion 317 of the vertical peripheral walls, and intermediate cover portion 333 that covers the intermediate region 315 of the vertical peripheral walls, wherein the proximal portion 316 transitions to the distal portion 317.
The portions 330, 331, 333 can be planar and the perimeter of the shield cover 311 can have generally vertical fingers or flaps or spring clips 334 and extend perpendicularly from the peripheral edge of the shield cover, wherein the fingers or flaps or spring clips 334 extend over the exterior sides of the vertical peripheral walls which can be understood from
As suggested earlier,
Experience with the surface-mounted radiofrequency shields has shown that it is difficult to wave-solder along the entire length of the walls of the individual rooms of the shield and testing has demonstrated that only certain critical areas need to be soldered. As such, a feature of the present principles includes providing a minimum number of contact points 520 along the individual vertical walls of each of the rooms of the shield. This reduces time and material usage and minimizes excessive handling which could also increase chances of inadvertent damage to components. As shown in the figures, the number of contact points along a complete linear wall segment of an individual room can be 3 or less. With the use of the disclosed principles, a single shield that has multiple heights can be used, although the present principle can effectively be utilized with a single height shield. In sum, the proposed principles involves locating appropriate pin locations on the shield having single height walls or multiple height walls and appropriate mating hole locations in the printed circuit board at the critical points and connecting the pins to the board with solder paste applied by the standard surface-mounted technology which can be a reflow process in the area of the pins to provide a sufficient connection once the assembly has been processed through the reflow oven. Testing has shown the solder pins or feet 502 are ideally about ˜0.8 mm long when the thickness of the printed circuit board is 1 mm. The holes can penetrate through the board and can have a diameter that is only slightly larger in width than the pins to the extent that they must fit the pins and be large enough to account for tolerances in the pin positions so that 100% of the pins in 100% of the assemblies will properly enter the holes. The holes can be elliptically shaped to have the long dimension be 110-200% of the long lateral dimension of the pin such that pins can be easily accommodated when the pins have a flat vertical geometry commensurate with the wall from which they extend. The holes can have the short lateral dimension being larger than the thickness of the shield wall and can be about 110-200% of the short lateral dimension of the pin. If the pins are round, the holes can be round and have a diameter of about 110-200% of the diameter of the pin. The benefit of elliptical shapes for the holes is they permit some limited lateral adjustments or lateral shifting of the pins that are rectangular in shape along the major and minor axis of the ellipses, but they do not permit substantial rotation or twisting of the pins and the shield.
Some additional features of the current principle can include reflow-soldering the shield at solder points at a limited number of specific areas; reflow-soldering the shield with “over pasting” to increase the amount of solder at only the limited number of locations which can be the critical areas that include the plated holes; reflow-soldering the shield with at least one component that could not be soldered in a wave-solder process, which, for example, can be the tuner F-connector center pin 507 as seen in
The current principles are intended to include situations in which the solder paste is only applied to hole regions and intended to include other situations in which a wall of solder is needed for performance purposes along some shield walls, but the other shields only require the limited number of contact points 520.
An aspect of the present principle includes the method in which an electronic device is constructed. The method is described in
Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present principles is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope of the present principles. All such changes and modifications are intended to be included within the scope of the present principles as set forth in the appended claims which can mean that for the process steps disclosed herein the particular and specific order of the steps can be rearranged or reordered where practical and be within the scope of the present principles.
Also, it is intended that the expressions “rear” and “front” and the expressions “vertical” and “horizontal,” as well as other complementary terms are intended to be construed from the perspective of the observer of the figures; and as such, these expression can be interchanged depending upon the direction that the observer looks at the device.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/010,251, filed Jun. 10, 2014, which is incorporated by reference herein in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/034381 | 6/5/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62010251 | Jun 2014 | US |
