Patent Application
20130286189
The present disclosure generally relates to inspection devices, and particularly to an inspection device for inspecting solder deposited in holes in printed circuit boards (PCBs) with through-hole electronic components. In the manufacture of electronic assemblies, through-hole mounting refers to the mounting scheme used for electronic components that use leads on the components. The leads are inserted through holes in printed circuit boards (PCBs) either by hand placement or by the use of automated insertion machines and then soldered to the PCBs.
Manufacturing defects are common during the soldering process. If solder does not completely fill the hole in the PCB, the electrical and/or mechanical connection will not be as strong as it could be. Therefore, it is important to inspect the solder following the soldering process to determine whether the solder has completely filled the hole.
One method of identifying defective soldering uses a technology known as automated optical inspection (AOI). AOI technology generally utilizes a light source for perpendicularly projecting light beams onto the surface of the solder, and a camera for capturing light beams reflected from the solder, thereby generating an image of the solder. However, these machines often fail to detect small unacceptable voids in the solder, or falsely indicate that a good solder is defective.
Therefore, it is desired to provide an imaging device for reliably inspecting solder.
To overcome this problem, there is provided a method and apparatus to inspect at least one solder connection for a through-hole component mounted on a printed circuit board. The invention includes a light source and a camera or light sensor mounted in diametrical opposition to one another. The printed circuit board with the at least one solder connection corresponding to a through-hole mounting on a printed circuit board is passed between the light source and the camera or light sensor. If light is detected then the solder connection is defective.
Other aspects of the invention may include building upon this by having a diffuser screen positioned between the light source and the camera and having the PCB with the through-hole mounting pass between the camera and the diffuser screen.
In yet another aspect of the invention an apparatus may be provided to detect defective solder connections on multiple assemblies at the same time. Each assembly would include a PCB with at least one through-hole mounting with a solder connection. The apparatus may utilize a tray to hold the multiple assemblies in place and which moves the tray between the light source and camera or light sensor. The detection of light through any through-hole mountings for the multiple assemblies would indicate a defective solder connection for that particular Assembly.
In yet a further aspect a computer, software, and a display may be provided to image one or more assemblies and to image a defective or an acceptable assembly. The software on the computer would be configured to convert signals from the camera for the construction of an image of the assemblies. The software is further configured to analyze the image to identify a defective solder connection and to identify on a display the location where a defective solder connection is found.
Numerous other advantages and features of the invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims, and from the accompanying drawings.
A fuller understanding of the foregoing may be had by reference to the accompanying drawings, wherein:
While the invention is susceptible to embodiments in many different forms, there are shown in the drawings and will be described herein, in detail, the preferred embodiments of the present invention. It should be understood, however, that the present disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the spirit or scope of the invention and/or claims of the embodiments illustrated.
In the following description, for simplicity, it will be assumed that there is only one solder connection. Furthermore, in the following description, a “defect” or “defects” may include at least one portion of the solder having too little solder, solder irregularly distributed, no solder, or any combination of these defects.
In a first and preferred embodiment there is provided a method in accordance with one aspect of the present invention. The method includes the steps of providing a light source and a camera or light sensor positioned such that the two are diametrically opposed. A printed circuit board (PCB) or assembly having at least one through-hole mounting component and solder connection is passed between the light source and the camera or light sensor. Inspection of the solder connection is then made and if light is detected then the solder connection is defective. The inspection can be done manually or automatically. If done automatically, a machine or apparatus would detect the light through the solder connection indicating that the connection was not correctly soldered and then providing an indication either on a display or an audible indication that the assembly or PCB has a defective solder connection.
Referring now to
In other variations, at least one light source 56 can be an array of light emitting diodes 58, one LED for each solder connection. The light source 56 can also be positioned within a channel 60 defined within the notched section 52 to help ensure the light source 56 does not interfere with the placement of the assembly 10. In addition, a camera or light sensor can be positioned opposite the light source to aid in detecting any defective solder connections.
Referring to
The apparatus 100 includes a camera 120 or light sensor and a light source 130. It may also include, but does not necessarily require a display 110 and a computer (not shown) having software configured to run the particular items as described herein. The computer and display may be separable components or designed together as a PDA, laptop, tablet computer, etc.
The light source 130 is capable of projecting light towards the assemblies 10 and more particularly towards the through-holes and into the solder connection 22. The camera 120 or light sensor is mounted diametrically opposed to the light source 130. As such the camera 120 and light source 130 may be mounted in any particular orientation (up/down or side/side or any angled combination thereof); as long as the two diametrically oppose each other. The assembly 10 is then moved between the light source 130 and the camera 120, such that the light projects towards the through-holes and into the solder connection 22. Once captured by the camera or detected by the light sensor, the software is configured to convert the signals, and construct an image by processing the electrical signals.
Once positioned between the camera and the light source, an image of the assembly is taken. The software is configured to detect any light filtering through the solder connection 22. A display 110 can be configured to show an image 112 of one or more of the assemblies 10 and may indicate a pass/fail notice 114 over the assembled component 10.
The light source 130 may include a diffuser panel 132 or diffuser screen and bulbs 134. It has been found that light through the diffuser panel 132 helps evenly distribute the light over all of the assemblies.
The apparatus may be designed as part of a housing construct 150 positioned to hold the camera and light source and positioned if desired over a conveyor belt system 160. The conveyor belt system 160 would be designed to move the assemblies 10 across the light source 130 and through the housing construct 150. The housing construct 150 may include a hinged front panel 152 to provide access to the camera 120 or light sensor and the lighting source 130.
The assemblies 10 may, but do not necessarily have to be placed in a tray 180 and held in position by the tray. The tray 180 includes at least one edge 182 that meshes to an edge 162 of the conveyor belt system 160 such that when the conveyor belt system 160 moves the tray 180 moves through the housing construct 150 and between the light source 130 and the camera 120. The apparatus is configured as described above such that the camera and/or display can be used to help detect defects. As soon as the tray is moved out of the housing construct, the operator can remove the failed assembly and determine if the assembly 10 needs to be re-soldered. A visual check of the solder connection 22 may show that the assembly 10 includes a missing solder connection 23 (
The tray 180 includes a plurality of testing stages 200, each testing stage 200 is designed to receive and hold an assembly 10 in position. Each testing stage may include a stage electrical testing component 210 to engage an assembly 10. Each stage electrical testing component would typically be configured to facilitate electrical testing of the assemblies while the assemblies are mounted in the tray. This can be done separately and apart from the inspection of the solder connections. In addition when secured to the stage electrical testing component, the assembly is positioned over an opening 220 such that when the tray 180 passes over the diffuser 132 the light source will project the light into the assembly 10 and illuminate through any defects in the solder connection 22 allowing the camera 120 or light sensor and an operator reviewing the display 110 to identify any defective solder connections 23.
From the foregoing and as mentioned above, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the novel concept of the invention. It is to be understood that no limitation with respect to the specific methods and apparatus illustrated herein is intended or should be inferred.
