Patent Application
20130014977
The present invention relates to an approach that detects plated through hole voids in printed circuit boards using a luminescent component bound to a glass fiber layer of a circuit board.
Plated through hole voids are a known issue when manufacturing printed circuit boards (PCB). Plated through hole voids may potentially cause failure during assembly and are also considered as a long term reliability issue of the printed circuit boards. Current understanding of the phenomenon indicates that the voids typically form during composite copper plating before external circuitization. For example, voids may form if the copper plating solution was blocked by air bubbles, foreign material, or dry film resist residues. During that period, the entire PCB is virtually encased in copper. The only areas where laminate would be exposed is at a defect site where there is a void in the copper. This defect is difficult to detect using currently-available inspection capability or test equipment. The voids may not entirely encircle the hole wall and thus may not result in an electrical open thereby making it difficult to detect by an electrical method. In the subsequent card assembly and field application processes, these voids may become an intermittent open, or even a dead open, due to high thermal stress in the assembly process or temperature cycling during the application stage.
An approach is provided in detecting plated-through hole defects in printed circuit boards (PCBs). The printed circuit board is exposed to a modified-silane solution. The modified-silane solution has a luminescent moiety and the modified-silane solution binds to exposed glass within a glass fiber layer of the printed circuit board. Plated-through hole defects are identified in the printed circuit board by detecting a luminescence at a surface location of the printed circuit board. Each surface location where the luminescence is detected corresponds to one of the plated-through hole defects.
The foregoing is a summary and thus contains, by necessity, simplifications, generalizations, and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the present invention, as defined solely by the claims, will become apparent in the non-limiting detailed description set forth below.
The present invention may be better understood, and its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings, wherein:
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.
Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).
Aspects of the present invention are described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.
The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
The following detailed description will generally follow the summary of the invention, as set forth above, further explaining and expanding the definitions of the various aspects and embodiments of the invention as necessary. To this end, this detailed description first sets forth a computing environment in
Northbridge 115 and Southbridge 135 connect to each other using bus 119. In one embodiment, the bus is a Direct Media Interface (DMI) bus that transfers data at high speeds in each direction between Northbridge 115 and Southbridge 135. In another embodiment, a Peripheral Component Interconnect (PCI) bus connects the Northbridge and the Southbridge. Southbridge 135, also known as the I/O Controller Hub (ICH) is a chip that generally implements capabilities that operate at slower speeds than the capabilities provided by the Northbridge. Southbridge 135 typically provides various busses used to connect various components. These busses include, for example, PCI and PCI Express busses, an ISA bus, a System Management Bus (SMBus or SMB), and/or a Low Pin Count (LPC) bus. The LPC bus often connects low-bandwidth devices, such as boot ROM 196 and “legacy” I/O devices (using a “super I/O” chip). The “legacy” I/O devices (198) can include, for example, serial and parallel ports, keyboard, mouse, and/or a floppy disk controller. The LPC bus also connects Southbridge 135 to Trusted Platform Module (TPM) 195. Other components often included in Southbridge 135 include a Direct Memory Access (DMA) controller, a Programmable Interrupt Controller (PIC), and a storage device controller, which connects Southbridge 135 to nonvolatile storage device 185, such as a hard disk drive, using bus 184.
ExpressCard 155 is a slot that connects hot-pluggable devices to the information handling system. ExpressCard 155 supports both PCI Express and USB connectivity as it connects to Southbridge 135 using both the Universal Serial Bus (USB) the PCI Express bus. Southbridge 135 includes USB Controller 140 that provides USB connectivity to devices that connect to the USB. These devices include webcam (camera) 150, infrared (IR) receiver 148, keyboard and trackpad 144, and Bluetooth device 146, which provides for wireless personal area networks (PANs). USB Controller 140 also provides USB connectivity to other miscellaneous USB connected devices 142, such as a mouse, removable nonvolatile storage device 145, modems, network cards, ISDN connectors, fax, printers, USB hubs, and many other types of USB connected devices. While removable nonvolatile storage device 145 is shown as a USB-connected device, removable nonvolatile storage device 145 could be connected using a different interface, such as a Firewire interface, etcetera.
Wireless Local Area Network (LAN) device 175 connects to Southbridge 135 via the PCI or PCI Express bus 172. LAN device 175 typically implements one of the IEEE 802.11 standards of over-the-air modulation techniques that all use the same protocol to wireless communicate between information handling system 100 and another computer system or device. Optical storage device 190 connects to Southbridge 135 using Serial ATA (SATA) bus 188. Serial ATA adapters and devices communicate over a high-speed serial link. The Serial ATA bus also connects Southbridge 135 to other forms of storage devices, such as hard disk drives. Audio circuitry 160, such as a sound card, connects to Southbridge 135 via bus 158. Audio circuitry 160 also provides functionality such as audio line-in and optical digital audio in port 162, optical digital output and headphone jack 164, internal speakers 166, and internal microphone 168. Ethernet controller 170 connects to Southbridge 135 using a bus, such as the PCI or PCI Express bus. Ethernet controller 170 connects information handling system 100 to a computer network, such as a Local Area Network (LAN), the Internet, and other public and private computer networks. Luminometer 143 is a luminescence detection device that is capable of detecting luminescence on an object, such as a printed circuit board (PCB). In the embodiment shown, the luminometer is connected to the information handling system using one of the USB connections provided by USB Controller 140. Other embodiments may be utilized in which luminometer 143 is included in the information handling system using a different interface provided by the information handling system.
While
The Trusted Platform Module (TPM 195) shown in
The PCB is then scanned by luminometer 143 in order to detect any luminescence caused by any exposed glass fiber bundle ends on the PCB. The detection of a luminescence on the surface of the PCB identifies locations of plated-through-hole (PTH-void) defects in the PCB (defect detection 350).
In
One preferred embodiment of the invention uses trialkoxysilanes to form the plugs. There is a wealth of information detailing the coupling reaction of the alkoxy silanes to glass surfaces, so this reaction is well understood. However, other species that chemically bind to glass and that can be polymerized can be used in the invention.
In one embodiment of the invention, colored silanes are used to form the plug. In another embodiment of the invention, a luminescent compound is not used, and the plug is sensed based on the level of transmitted light through the plated-through hole.
In the instant disclosure, R—Si—(OCH3)3 in hydrolysis phase 410 of reaction scheme 400 is replaced with one of the representative silanes discussed below. The trialkoxy silane is pre-hydrolyzed via elimination of alcohol (either methanol or ethanol) to form the trihydroxy silane. Depending on the pH, temperature, silane concentration, etc., condensation (phase 420) of the trihydroxy silane results in a pre-polymer which couples to the active glass surface via hydrogen bonding to surface hydroxyl groups. A subsequent thermal bake drives off water to form an Si—O-glass covalent bond. At this phase, the luminescent silane is firmly bound to the glass surface and cannot be easily removed. Unbound silane (in PTHs without voids) can be readily rinsed free of the PTH. Suitable silanes for this process are methyl (1-pyrenyl)dimethylethyl (2-triethylsiloxy)silane and methyl 1(1-pyrenyl)dimethylethyl (1-triethylsiloxy)silane as disclosed in U.S. Pat. No. 4,746,751. Additionally, the photoactive perylenediimide-bridged silsesquioxane disclosed in Chem. Mater. 2005, 17, 2234-2236, shown below, can also be used in this reaction scheme. The aforementioned silanes are examples and the concept of detecting luminescence at a surface location is not limited to the aforementioned silanes. Any alkoxy-substituted silane incorporating a luminescent moiety may be used. The silanes may be deposited from aqueous solution where the trialkoxy groups will condense with surface silanols on the exposed glass fiber to form a siloxane bound to the fiber. Adjustment of the process parameters enables polymerization of the silane and formation of a luminescent, crosslinked gel or ‘plug’. The PCB is subsequently rinsed to remove uncoupled silane from the PTHs. The plugged hole of the PCB can then be detected by applying backlighting inspection techniques or other similar techniques, including use of a luminometer to detect the luminescence at the PCB surface locations of the PTHs.
At step 570, luminescence areas on the PCB surface are detected. In one embodiment, the luminescence is detected using a luminometer that is connected to an information handling system. In one embodiment, the luminescence areas are detected manually (visually) by an operator viewing the backlit PCB. A decision is made as to whether luminescence is detected at a surface location of the PCB (decision 575). If luminescence is detected at one or more surface locations, then decision 575 branches to the “yes” branch whereupon, at step 580, the PCB is noted as being defective due to the presence of one or more plated-through-hole defects. On the other hand, if no luminescence is detected, then decision 575 branches to the “no” branch whereupon, at step 590, the PCB is noted as not having any plated-through-hole defects.
While particular embodiments of the present disclosure have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, that changes and modifications may be made without departing from this disclosure and its broader aspects. Therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this disclosure. Furthermore, it is to be understood that the disclosure is solely defined by the appended claims. It will be understood by those with skill in the art that if a specific number of an introduced claim element is intended, such intent will be explicitly recited in the claim, and in the absence of such recitation no such limitation is present. For non-limiting example, as an aid to understanding, the following appended claims contain usage of the introductory phrases “at least one” and “one or more” to introduce claim elements. However, the use of such phrases should not be construed to imply that the introduction of a claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an”; the same holds true for the use in the claims of definite articles.
