PROCESS FOR MANUFACTURING PRINTED CIRCUIT BOARDS AND A MACHINE FOR THIS PURPOSE
Process and machine for manufacturing printed circuit boards wherein a press packet comprised of at least two press plates of metal material between which is arranged a printed circuit board composition formed by one or more metal sheets, by one or more layers of insulating material impregnated with polymerizable resins and/or by one or more printed circuit boards with an engraved image of a circuit, are arranged between the press plates of a press and is pressed, subjecting said press packet to the action of a variable induction magnetic field which generates induced currents in each metal plate and sheet of the press packet, causing the heating of said plates and sheets, in turn causing the heating by thermal conduction of the layers of insulating material, melting and liquefying the resins in said layers of insulating material and adhering the insulating material to the metal sheets, so that, on raising the temperature even more, the polymerizable resins in the layers of insulating material are then polymerized, resulting, after the cooling of the press packet, in one or more rigid boards suitable for making printed electronic circuits. The machine to carry out the above process comprises a variable induction magnetic field generating device adapted to generate induced currents in the press packet's metal plates and sheets, causing them to heat, and means of controlling the operation of the magnetic field generating device and controlling the temperature and pressure to which the press packet is subjected.
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This is a Divisional Application of U.S. application Ser. No. 10/549,040 filed Sep. 15, 2005, which is a National Stage entry of PCT/EP2004/002072 filed Mar. 2, 2004 which claims priority from ES P 200300717 filed Mar. 27, 2003. The disclosures of each of the above applications are incorporated herein by reference in their entirety.
TECHNICAL FIELD OF THE INVENTIONThe aim of the invention is a process for manufacturing printed circuit boards and a machine to carry out said process.
BACKGROUND OF THE INVENTIONPrinted circuit boards may take on multiple functional compositions, essentially concerning the number of metal sheets with an image of the circuit they form. So, for example, and among other forms, a board composition is initially formed from a metal sheet and a layer of insulating material impregnated with polymerizable resin on which, once the resins are polymerized and the board is cooled until it is hard, an engraved image of the circuit is formed on the metal sheet; another board composition is formed initially by two metal sheets between which there are one or more layers of insulating material; and a third composition for a printed circuit board is initially formed by two metal sheets between which there are two layers of insulating material separated by a printed circuit board provided on both faces with the already engraved image of the circuit.
In general, the process of polymerizing the resins in the layers of insulating material is carried out by subjecting the board whose composition has been disclosed to pressure at the same time as the temperature is raised until it reaches polymerization temperature. To do this, presses are used which are essentially differentiated by the method of heating the boards. One type of press includes means of heating arranged on the press plates of the press, so that the board is heated during pressing by thermal conduction. Another type of press includes means of heating based on passing an electric current supplied by a power source—generally direct current—through the board's sheets; in this case, the metal sheets are arranged continuously in order to make it possible for the electric current to pass through.
There are drawbacks with the types of press disclosed above. In presses wherein the means of heating are arranged on the press plates, the rate of temperature increase and the maximum temperatures that can be reached are very limited, which leads to low productivity. And, in presses where the means of heating are based on passing an electric current through the board's metal sheets, problems of electrical insulation between these and intermediate press plates arise.
EXPLANATION OF THE INVENTIONIn the process for manufacturing printed circuit boards which is the object of the invention, a press packet comprising at least two press plates of metal material between which are arranged a printed circuit board composition formed by one or more metal sheets, one or more layers of insulating material impregnated with polymerizable resins and/or by one or more printed circuit boards with an engraved image of the circuit, are arranged between the press plates of a press, and it is pressed.
The process is essentially characterized in that, maintaining pressure on the packet, it comprises the steps of
i) subjecting the press packet to the action of a variable magnetic induction field which generates induced currents in each of the press packet's metal plates and sheets that heat said plates and sheets, heating, in turn, the layers of insulating material by thermal conduction;
ii) raising the temperature in the press packet until the resins in the layers of insulating material melt, liquefying and flowing, and providing adhesion between the layers of insulating material and the metal sheets;
iii) raising the temperature in the press packet until it exceeds that of the previous phase ii), so that the polymerizable resins in the layers of insulating material are polymerised;
iv) proceeding to cool the press packet until the layers of insulating material have hardened; and finally removing the press packet from between the press plates of the press and separating the press plates from the rigid board or boards obtained.
It is also characteristic of the process that the printed circuit board or boards with an engraved image of the circuit that may form part of the press packet composition are obtained according to the invention process.
Another characteristic of the process is that the metal sheets of the press packet are made of copper and/or aluminium.
According to another aspect of the invention, the layers of insulating material are formed from fibre glass paper and/or material impregnated with epoxy resins, polyamides, phenolic resins or fluoropolymers (PTFE).
In accordance with another characteristic of the invention process, the press packet is vacuum pressed.
The machine for the invention process comprises a closed structure provided with at least one press unit comprised of an upper press plate capable of vertical displacement in both directions, activated by means of propulsion, and by a lower press plate arranged coaxially with respect to the upper press plate, fixed to the press structure or capable of vertical displacement in both directions, the upper and lower plates lacking any device to provide heat and being adapted to receive a press packet between them, in accordance with the invention process.
In essence, the machine is characterized in that it comprises a variable induction magnetic field generating device, adapted to generate induced currents in the press packet's metal plates and sheets causing them to heat, and means of controlling the operation of the magnetic field generating device, which essentially affect the frequency and voltage applied to the device and the temperatures reached in the press packet, and means of controlling the pressure to which it is subjected.
According to a preferred embodiment, the machine comprises means for producing a vacuum inside the closed structure.
Another characteristic of the invention is that the machine is provided with a variable induction field generation device, without a magnetic core, formed by induction coils within which the upper press plate and the lower press plate are arranged.
The characteristics of the invention process and machine provide an innovative solution to the problems created by both the known processes and machines for manufacturing printed circuit boards. With the invention process, the heating of the press packet's metal sheets by electromagnetic induction has the following advantages: it produces uniform heating in the press packet, and it is virtually possible to achieve any rate of temperature increase of the press packet and any polymerization temperature necessary for the resins used. The temperature reached by the press packet is easily controlled and regulated by controlling the voltage and/or frequency of the electrical power applied to the circuit generating the magnetic field. It can be applied to any press packet composition without loss of performance concerning temperature or temperature regulation thereof; and it does not require intermediate press plates to be equipped with electrical insulation, as occurs in those embodiments of presses based on passing a current through the metal plates forming the press packet.
By way of a non-limiting example, the attached drawings illustrate various compositions of printed circuit boards which can be obtained using the invention process as well as an embodiment of the machine for the invention process. In said drawings:
In the following description of the invention process and machine therefor, identical reference numbers are used by way of simplification to designate identical or similar parts.
The press plates used to carry out the process are made of metal material, such as aluminium or steel, and preferably magnetic steel.
Likewise, the result of the process, according to the invention, is optimum when the metal sheets used to produce the circuit boards are made of copper and/or aluminium.
The faces of the metal sheets intended to be in contact with the layers of insulating material are mechanically or chemically treated to increase their roughness and adherence to said layers of insulating material.
Alternatively, the surface of the metal sheets used and intended to be in contact with the layers of insulating material may be impregnated with adhesives or resins, also to increase the adherence of the metal sheets to the insulating material used.
As indicated above, in
The machine of the invention represented diagrammatically in
The times and temperatures required to polymerize the resins which may be used in the manufacturing process of the boards depend on the composition of the resins and the pressure applied to the press packet. For this reason, the machine is provided with a pressure regulator 71 and with one or more temperature probes 72. The information obtained by the pressure regulator and temperature probes is used to govern the machine's means of control 69.
Claims
1. An apparatus comprising:
- an upper press plate which is capable of vertical displacement;
- a lower press plate arranged coaxially with respect to the upper press plate, said lower plate being capable of vertical displacement, the upper and lower plates lacking any device to provide heat and being adapted to receive a press packet between them;
- a variable induction magnetic field generation device adapted to apply a variable induction magnetic field in a transverse direction of the press packet, said variable induction magnetic field running generally parallel to the planar surfaces of the press packet and generating induced currents causing heating in the press packet;
- a control circuit which controls the frequency and voltage applied to the electromagnetic field generation device, the temperature of the press packet, and the pressure to which the press packet is subjected.
2. The apparatus of claim 1, further comprising temperature probes adapted to be mounted on the press packet.
3. The apparatus according to claim 1, further comprising a vacuuming part which produces a vacuum inside a closed structure of the apparatus.
4. The apparatus according to claim 1, wherein the variable induction field generation device is provided without a magnetic core, and is formed by induction coils within which the upper press plate and the lower press plate are arranged.
Type: Application
Filed: May 29, 2009
Publication Date: Oct 8, 2009
Applicant: Chemplate Materials, S.L. (Santa Perpetua de Mogoda)
Inventors: Victor LAZARO GALLEGO (Santa Perpetua de Mogoda), Jose Antonio Cubeiro Gonzalez (Santa Perpetua de Mogoda)
Application Number: 12/474,739
International Classification: H05B 6/06 (20060101); H05B 6/10 (20060101);