Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2002-10-16
2004-05-04
Vigushin, John B. (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S258000, C174S260000, C361S812000, C361S813000
Reexamination Certificate
active
06730854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin-formed substrate in which a metal frame patterned in shape of a circuit pattern by press working, etching, or the like is encapsulated with a resin.
2. Related Background Art
In recent years, there are growing demands for miniaturization and extension of functionality of electronic equipment, and technological development is under way toward miniaturization and higher performance of printed circuit boards. Research is being made in high density mounting based on realization of multilayer structures of printed circuit boards and thinner line structures of wiring patterns, and miniaturization is also under way for electronic components themselves to be mounted on the boards. There has been a growth in use of the surface mounting type without leads.
On the other hand, in the case of the printed wiring boards in the field of electronic equipment working with a large electric current like a large inverter control circuit or a primary power circuit, the circuit pattern is formed of a very thin copper foil in the thickness of 0.18 to 0.7 &mgr;m on a glass fabric based epoxy resin or paper based phenolic resin. For this reason, the area of the circuit pattern has to be increased in order to increase the current capacity, and electronic components and wiring patterns have to be set apart from each other over a certain distance in order to ensure sufficient reliability of electrical insulation. These were the hindrance to the development of high density mount technology and delayed the miniaturization of the printed circuit boards with such a large current control as the large inverter control circuit or the primary power circuit, which resulted in hindering the miniaturization of electronic equipment.
Furthermore, the printed circuit boards with the large current control as described above often carry large and heavy electronic components such as inductors, relays, and the like, and frequently suffer such failure that lands (electrode portions) of the printed wiring board with electronic components soldered there are peeled off because of vibration or the like. For securely fixing the electronic components on the printed board, it is possible to use an adhesive. However, this method requires a production process except for soldering and use of the adhesive in addition to solder, which largely increases the processing cost. Therefore, it was not practical.
In order to achieve the miniaturization while overcoming the above problem, there are proposals on a resin-formed substrate such as a resin-molded substrate in which a metal frame having a circuit pattern formed therein is coated with a resin, as described in Japanese Patent Application Laid-Open No. 2000-133897. The resin-formed substrate is formed in such a way that a thin plate of copper-or brass normally about 0.5 mm thick is processed in shape of a desired circuit pattern by press working or etching to obtain a metal frame and that the metal frame is encapsulated with a resin about 1.0 mm thick by insert molding. Since the thickness of the thin plate of copper or brass allowing flow of electric current is larger than those of the ordinary printed wiring boards, it is feasible to construct the large current circuit pattern of a finer pattern and achieve higher density of the circuit pattern. The substrate is also excellent in electrical insulation, because the metal frame is coated with a resin. Accordingly, the substrate of this type is particularly effective to construction of the primary electronic circuit pattern board working with the alternating current of high current intensity like the inverter circuit such as the power circuit pattern or the like.
The injection molding machine with high production efficiency is used in the resin molding for coating the metal frame, and the resin material is normally PPS (polyphenylene sulfide) or PBT (polybutylene terephthalate). Since the metal frame has the lands (electrode portions) for the electronic components to be connected and soldered at predetermined positions, circularly opening land apertures for exposing the lands are provided in the surface of the resin-formed substrate.
A flow soldering technique of implementing soldering with molten solder is used as a method of soldering the electronic components to the resin-formed substrate. The flow soldering technique is a method of blowing the molten solder off over a solder bath, transporting the resin-formed substrate with the electronic components mounted thereon, to over the solder bath, and bringing a solder side as a back surface of the resin-formed substrate into contact with the molten solder blowing off, thereby soldering the leads from the electronic components. In this method, a flux is preliminarily applied onto portions subjected to soldering on the resin-formed substrate, in order to achieve good soldering of the components to the resin-formed substrate. The flux is applied using a flux applying device called a fluxer. Many resin-formed substrates are planar, and the flow soldering technique is normally used for the soldering thereof.
However, while the electronic components are soldered to the resin-formed substrate by the flow soldering technique, the resin-formed substrate is heated only on the solder side thereof by the molten solder blowing off. The resin-formed substrate has a component side for mounting the electronic components thereon, and a solder side for soldering the electronic components thereto, and each of the two sides is coated with a resin about 1.0 mm thick. For this reason, heat on the solder side is hard to transfer to the component side, so that a temperature difference is made between the component side and the solder side. This posed a problem that the resin-formed substrate was warped. This deformation raised significant influence, particularly, when the resin-formed substrate had a large area.
In addition, the resin-formed substrate is difficult to print a component silk thereon, unlike the ordinary printed wiring boards. Therefore, in a step of mounting the electronic components on the resin-formed substrate, it is difficult to specify mounting positions of the electronic components. This might cause mounting of the electronic components at incorrect positions or require a lot of time for specifying the mounting positions, which heavily lowered workability.
In order to achieve secure soldering in the aforementioned flow soldering technique, it is important to preliminarily even the lengths of the leads of the electronic components projecting on the solder side. However, since the lengths of the leads of the electronic components mounted on the resin-formed substrate are different depending upon types and sizes of the electronic components, the leads of the electronic components have to be preliminarily cut in predetermined length before the components are mounted on the resin-formed substrate. The lead cut operation of preliminarily cutting the leads according to the lengths of the leads for the respective electronic components, however, increases the production cost of the resin-formed substrate.
The electronic components can also include a component to which the lead cut operation is applicable with difficulty, e.g., a large electronic component like an interlock relay for large electric current. In this case, it is necessary to provide a space between the electronic component and the resin-formed substrate, to place an insulator between the electronic component and the resin-formed substrate, or to design the mount position of the electronic component on the resin-formed substrate so as to take a long creepage distance for insulation equivalent to the lead cut length. These countermeasures all result in failure in secure mounting of the electronic component, increase in the production cost, and hindrance to the miniaturization of the resin-formed substrate, however.
Meanwhile, in the case where a relatively large component, e.g., an inductor of large diameter, had to be mounted on the resin-form
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Vigushin John B.
LandOfFree
Resin-formed substrate and resin-formed substrate unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Resin-formed substrate and resin-formed substrate unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Resin-formed substrate and resin-formed substrate unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3217880