Patent Application
20210051802
Not Applicable.
This disclosure relates to surface-mount devices and improvements in surface-mount technology.
Surface-mount technology has been generally limited to installation of electronic devices onto a printed circuit board, with non-electronic, functional components being added in separate steps using different technology.
U.S. Pat. No. 8,585,242 describes a securement ring adapted to hold a lens and which is surface mountable to a printed circuit board.
This disclosure provides methods of using surface-mount technology to install optical components on a printed circuit board. The method can allow optical components to be installed on a printed circuit board simultaneously with electronic components to reduce the number of steps and/or the technologies needed to assemble certain devices.
Described herein are optical components that are mountable to a printed circuit board (PCB) using surface-mount technology in which solder reflow is used to permanently secure the optical component to the PCB. The optical components are supported by or integrated onto a surface mount device having a dielectric body and a solderable support connected with the dielectric body. As used herein, the term “optical component” includes lens, reflectors, filters, and polarizers.
A surface-mount device 10 having a dielectric body 12 defining functional features 14, and a lead frame clip 15 is shown in
The lead frame clip 15 is shown by itself, separated from the dielectric body 12 in
Lead frame clip 15 includes a generally rectangular frame comprising longitudinal members 16, transverse solder pad members 18, and upstanding clip 20 having upper inwardly turned lips 22 that engage ledges at upper ends of side walls 24 of body 12. The lengths of longitudinal members 16 are substantially the same as the length dimension (L) of body 12 (
The term “dielectric”, as used herein, refers to a material having an electrical conductivity that is less than that of typical semi-conductive materials, and can refer to those materials having an electrical conductivity that is less than 10−6 Ohm-meter. Suitable di-electrical materials from which body 12 can be fabricated include various polymeric (plastic) materials, ceramics, and glass. Particularly preferred are plastic materials that can be injection molded, including polybutylene terephthalate, polyethylene terephthalate, poly cyclohexylene-dimethylene terephthalate (PCT), acrylonitrile-butadiene-styrene terpolymer (ABS), polycarbonates, polyacrylates, polymethacrylates, polyesters, long alkyl chain polyphthalamide (PPA). These plastic materials may contain various fillers to provide desired physical and/or mechanical properties. For example, titanium dioxide can be added to provide a white pigment and/or diffusively scatter light, carbon black can be added to create a black appearance and absorb light, or glass and/or minerals could be added to increase rigidity.
Body 12 can be provided with optical features 14. In the illustrated embodiment (
As seen in
Illustrated reflectors 14 are non-limiting examples of functional features that can be incorporated into the body 12. Other reflector designs, illustrated in
Surface-mount devices in accordance with this disclosure can also be used or modified to be used as component protectors, such as for LEDs, capacitive sensors or other electronic components, which can be located generally within or at a through-hole or aperture extending from a bottom surface of the surface-mount device adjacent a PCB on which the protected electronic component is mounted to a top surface.
The disclosed surface-mount devices can also be used in combination with a light pipe (optical wave guide) to efficiently propagate light from an LED to a display panel. Such arrangements can be used, for example, in billboard displays, stadium displays, or vehicle instrument panels. The light guide assembly 100 includes a PCB 102, an LED 104 mounted on the PCB, a surface-mount device 10 as described, and an optical wave guide 106.
In an alternative embodiment, the solderable support can be partially embedded within the dielectric body using insert molding techniques. In such case, for example, two solder pad members, one at each end of the device, can be provided with extrusions that are embedded within the dielectric body.
The surface-mount devices (SMD) can be installed using conventional surface-mount technology. For example, the SMD can be positioned over an electronic component on a circuit board either manually or using a pick-and-place machine. Prior to placement, a solder paste can be applied to solder pads on the SMD and/or to non-functional solder pads on the PCB to provide temporary fixation of the SMD to the PCB. Thereafter, the PCB with attached SMD can be placed in a solder reflow oven and heated to a temperature that melts the solder in the solder paste. After cooling, a strong physical connection is established. Alternatively, the electronic component and the SMD can be mounted simultaneously, such as by adhesively or mechanically fixing the electronic component to the SMD to form an assembly that is placed on the PCB and joined thereto using conventional service-mount technology.
While the present invention is described herein with reference to illustrated embodiments, it should be understood that the invention is not limited hereto. Those having ordinary skill in the art and access to the teachings herein will recognize additional modifications and embodiments within the scope thereof. Therefore, the present invention is limited only by the claims attached herein.
