JP2005153335A - Optical printer head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin optical printer head that provides a prescribed image corresponding to image data, is productive and has high accuracy. <P>SOLUTION: In the optical printer head, a light-emitting element array chip 5 having many light-emitting elements 7 and connecting pads 6 on the top face is stuck to the bottom of the concave portion 1a of the substrate 1 by an adhesive 4, and one end of a first circuit conductor 2 is electrically connected to the connecting pads 6 through a second circuit conductor 9 formed on the underside of a second circuit board arranged face to face on the top face of a first circuit board on a first circuit board made by forming a first circuit conductor 2 and an insulation layer 3 on a synthetic resin substrate 1. As a result, the optical printer head provides a good print quality, can be produced in volume and is reliable. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical printer head used as optical writing means for an electrophotographic printer or the like.

  Conventionally, an optical printer head typified by an LED array head has been used as an optical writing means for an electrophotographic printer or the like.

  As such a conventional optical printer head, for example, as shown in a sectional view in FIG. 3, a large number of light emitting elements 27 and a large number of connections are formed on the upper surface of a circuit board 21 on which a large number of circuit conductors 22 are adhered in a predetermined pattern. A plurality of light emitting element array chips 25 having pads 26 are mounted by arranging them in a line so that all the light emitting elements 27 are arranged in a straight line and bonding them with an adhesive 24, and connecting each light emitting element array chip 25 A structure in which the pad 26 and the circuit conductor 22 corresponding to the connection pad 26 are electrically connected by a bonding wire 32 or the like is known. According to this, the light emitting elements 27 are selectively made to emit light individually based on the image data from the outside, and the emitted light is irradiated to an external photoreceptor via an optical system such as a rod lens array (not shown). By forming an image and forming a predetermined latent image on the photoreceptor, it functions as an optical printer head.

  Then, the latent image formed on the photoconductor becomes a toner image through a development process, and a predetermined print is formed on the recording paper by transferring and fixing the toner image onto the recording paper.

  However, when the above-described conventional optical printer head is configured with, for example, an A3 size, 600 dpi (dot per inch) product specification, the connection point between the connection pad 36 and the circuit conductor 22 reaches about 15,000 points. Both are individually connected by as many as 15,000 bonding wires 32. Therefore, when these bonding wires 32 are bonded by a conventionally well-known wire bonding method, the connection work takes a very long time, and thus there is a problem that the productivity of the optical printer head cannot be improved. . Also, when using an optical printer head, etc., the bonding wire 32 may fall down due to external vibration or impact, causing the adjacent bonding wires 32 to be short-circuited, which reduces the reliability of the optical printer head. There was also a problem that I was allowed to.

  The bonding wire 32 in the conventional optical printer head described above is connected to the circuit conductor 22 and the connection pad 26 of the light emitting element array chip 25 by the wire bonding method. Second bonding is performed on the circuit conductor 22 side on the array chip 25 side. In this case, since a ball-shaped nail head is formed at the end of the bonding wire 32 bonded to the connection pad 26, a part of the light emitted from the light emitting element 27 is used when the optical printer head is used. Is reflected by the nail head of the bonding wire 32, and when such reflected light is irradiated onto an external photoconductor, an unnecessary latent image resulting from irradiation of the reflected light is formed on the photoconductor. Also, there is a problem that an accurate image corresponding to the image data cannot be obtained.

  Further, according to the conventional optical printer head described above, in order to connect the bonding wire 32 to the connection pad 26 of the light emitting element array chip 25, the connection pad 26 is used to connect the ball-shaped nail head of the bonding wire 32. 80 mm × 80 μm or more is required, so that the light emitting element array chip 25 cannot be reduced in size, and the number of chips when manufacturing a large number of chips from a single wafer substrate is reduced. Therefore, there is a problem that the price of the optical printer head using a large number of light emitting element array chips 25 cannot be reduced.

  In order to solve these problems, a collective wiring type optical printer head that does not use wire bonding has been proposed.

  Regarding such a collective wiring type optical printer head, the present applicant has proposed a new configuration in Japanese Patent Application No. 2002-167044. The contents will be described with reference to a cross-sectional view shown in FIG. 4 and an enlarged plan view of a main part shown in FIG.

4 and 5, reference numeral 41 denotes a substrate constituting the circuit board, 42 denotes a first circuit conductor, 43 denotes an insulating layer, 44 denotes a fixing adhesive, and 45 denotes a light emitting element array chip. 46 is a connection pad of the light emitting element array chip 45, 47 is a light emitting element, and 49 is a circuit conductor that electrically connects the first circuit conductor 42 and the connection pad 46 of the light emitting element array chip 45. Circuit conductor. According to the optical printer head shown in FIGS. 4 and 5, the recess 41a in which the light emitting element array chip 45 is embedded is formed on the upper surface of the substrate 41, and the light emitting element array chip 45 is fixed to the bottom of the recess 41a. In addition, the adhesive 48 is filled in the gap between the inner surface of the recess 41a and the side surface of the light emitting element array chip 45, and the insulating layer 43 on the substrate 41 and the upper surface 48a of the adhesive 48 are insulated. The circuit conductor 42 exposed from the opening 43a of the layer 43 is electrically connected to the connection pad 46 of the light emitting element array chip 45 by the second circuit conductor 49. As a result, when forming the pattern of the second circuit conductor 49, they can be connected simultaneously and collectively to the connection pads 46 of the light emitting element array chip 45, and these can be connected by wire bonding or the like. Compared to the case, the time required for the connection work can be shortened.
JP-A-1-34760 JP-A-1-208874 Japanese Unexamined Patent Publication No. 4-87383

  However, even in such a collective wiring type optical printer head, the thermal expansion coefficient of the light emitting element array chip 45, the thermal expansion coefficient of the substrate 41, the side surface of the light emitting element array chip 45, and the inner surface of the recess 41a of the substrate 41 When comparing the thermal expansion coefficient of the adhesive 48 filled between the adhesive 48 and the substrate 41, the thermal expansion coefficient of the adhesive 48 and the substrate 41 is usually much larger than the thermal expansion coefficient of the light emitting element array chip 45. In addition, depending on the thermal history of the process or the environmental temperature, the pitch of the chips varies among the plurality of light emitting element array chips 45, and in the extreme case, the second circuit conductor 49 may be disconnected. There are problems that need improvement.

  With regard to this problem, when the adhesive 48 and the substrate 41 are compared, the substrate 41 is filled with a filler, or by adjusting the amount of glass cloth, the desired electrical characteristics and mechanical properties. It is possible to adjust the thermal expansion coefficient to some extent without impairing the characteristics, but for the adhesive 48, if a means for adjusting the thermal expansion coefficient such as filling the filler is used, the fluidity becomes poor and the filling is poor. In many cases, there is a trade-off relationship between the thermal expansion coefficient and the desired characteristics, such as the tendency of occurrence of the phenomenon, and an improvement that does not depend on such adjustment means is desired.

  Further, since the adhesive 48 has an effect of fixing the positional relationship between the substrate 41 and the light emitting element array chip 45 by curing, when the working temperature is high or the difference in thermal expansion coefficient from the substrate 41 is large, the above-mentioned There was a problem that an improvement was desired that the defect would be further expanded.

  The present invention has been devised in view of the above-described problems, and the object thereof is to obtain a predetermined image corresponding to high-resolution image data, and has excellent productivity and high accuracy. It is to provide an optical printer head.

  The optical printer head according to the present invention has a large number of first circuit conductors provided on a resin substrate, and an upper surface on the first circuit substrate formed by coating an insulating layer on the first circuit conductors. An optical printer head having a light emitting element array chip having a large number of light emitting elements and connection pads and electrically connecting the first circuit conductor to the connection pads, wherein the light emitting elements are disposed on an upper surface of the substrate. A concave portion in which the array chip is embedded is formed, the light emitting element array chip is adhered to the bottom surface of the concave portion with an adhesive, and one end of the first circuit conductor is arranged to face the upper surface of the first circuit board. The second circuit board is electrically connected to the connection pad via a second circuit conductor formed on the lower surface of the second circuit board.

  The optical printer head of the present invention is characterized in that, in the above configuration, the second circuit board has the second circuit conductor formed on a lower surface of a flexible board.

  The optical printer head of the present invention is characterized in that, in each of the above configurations, the second circuit board is formed with a through hole in a portion corresponding to the light emitting element.

  The optical printer head of the present invention is characterized in that, in the above configuration, the second circuit board has the second circuit conductor formed on the lower surface of the translucent board.

  In the optical printer head of the invention having the aforementioned configuration, the second circuit conductor is electrically connected to one end of the first circuit conductor and the connection pad using an anisotropic conductive paste. It is characterized by being.

  According to the optical printer head of the present invention, a large number of first circuit conductors are provided on a resin substrate, and an insulating layer is coated on the first circuit conductors. An optical printer head having a light emitting element array chip having a large number of light emitting elements and connection pads on an upper surface and electrically connecting a first circuit conductor to the connection pads, wherein the light emitting element array chip is formed on the upper surface of the substrate. A second circuit in which a light emitting element array chip is bonded to the bottom surface of the concave portion with an adhesive, and one end of the first circuit conductor is disposed opposite to the upper surface of the first circuit board. Since it is electrically connected to the connection pad via the second circuit conductor formed on the lower surface of the substrate, it can be mounted without using wire bonding as in the prior art. No. 167044 While maintaining the good characteristics of the proposed structure, it does not use an adhesive filling between the inner surface of the recess and the side surface of the light emitting element array chip, so it fills between the substrate and the light emitting array chip and their side surfaces. The problem caused by the difference in thermal expansion coefficient with the applied adhesive, that is, the problem that the pitch between the light emitting element array chips varies, and in the extreme case, the second circuit conductor is disconnected. Points can be improved. Further, since the circuit conductor is not directly formed on the light emitting element array chip, it is possible to prevent the light emitting element array chip from being destroyed by a physical impact due to the formation of the circuit conductor. As a result, it is possible to provide an optical printer head having good print quality, capable of mass production, and high reliability.

  According to the optical printer head of the present invention, when the second circuit board has the second circuit conductor formed on the lower surface of the flexible board, the thickness of the second circuit board is reduced. Since it can be made thin easily and a light-transmitting base material can be used for the flexible substrate, light can be extracted efficiently. As a result, it is possible to provide an optical printer head having good print quality, capable of mass production, and high reliability.

  Further, according to the optical printer head of the present invention, when the second circuit board has a through hole formed in a portion corresponding to the light emitting element, the light from the light emitting portion is not blocked. The light can be extracted efficiently. As a result, it is possible to provide an optical printer head having good print quality, capable of mass production, and high reliability.

  According to the optical printer head of the present invention, when the second circuit board has the second circuit conductor formed on the lower surface of the translucent board, the second board using the translucent board is used. Since the light emitting element can be covered by the second circuit board, the light emitting element can be protected by the second circuit board. As a result, it is possible to provide an optical printer head having good print quality, capable of mass production, and high reliability.

  Further, according to the optical printer head of the present invention, when the second circuit conductor is electrically connected to one end of the first circuit conductor and the connection pad using the anisotropic conductive paste, the vertical direction That is, since the first circuit conductor and the second circuit conductor are connected only at a position where the first circuit conductor and the second circuit conductor are in perpendicular contact with each other, a short circuit in the lateral direction can be prevented. As a result, it is possible to provide an optical printer head having good print quality, capable of mass production, and high reliability.

  Hereinafter, an optical printer head of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing an example of an embodiment of the optical printer head of the present invention, and FIG. 2 is a cross-sectional view showing another example of the embodiment of the optical printer head of the present invention. In these drawings, the same parts are denoted by the same reference numerals, 1 is a resin substrate, 2 is a first circuit conductor, 3 is an insulating layer, and a number of first substrates are formed on the resin substrate 1. The first circuit board is formed by covering the first circuit conductor 2 with the insulating layer 3. Reference numeral 4 denotes a fixing adhesive, and 5 denotes a light emitting element array chip. The light emitting element array chip 5 is fixed to the bottom surface of the concave portion 1 a formed on the upper surface of the substrate 1 by the fixing adhesive 4. Yes. 6 is a connection pad of the light emitting element array chip 5, and 7 is a light emitting element. 8 is a substrate such as a flexible substrate constituting the second circuit board, 9 is a second circuit conductor, and the substrate 8 and the second circuit conductor 9 constitute a second circuit board. Yes. Reference numeral 10 denotes a through-hole such as a slit formed in a portion corresponding to the light-emitting element 7 of the substrate 8, and 11 denotes a translucent reinforcing substrate such as a cover glass.

  The substrate 1 constituting the first circuit board is made of, for example, a resin such as a glass cloth base epoxy resin, a glass cloth base BT (bismaleimide / triazine) resin, or a glass cloth base polyphenylene ether. A large number of first circuit conductors 2 functioning as power supply wirings for supplying power to the light emitting elements 7 on the light emitting element array chip 5 are formed on the upper surface of the substrate 1. These first circuit conductors 2 are made of a metal such as copper, for example.

  Next, between the first circuit conductors 2 and between the first circuit conductors 2 and the second circuit conductors 9 to be formed later, the corrosion of the first circuit conductors 2 is prevented and protected. An insulating layer 3 is formed. The insulating layer 3 is made of, for example, an epoxy resin, an acrylic resin, a phenol resin, or the like.

  Further, on the upper surface of the substrate 1, the light emitting element array chip 5 and a depth substantially equal to the thickness of the fixing adhesive 4 for fixing the light emitting element array chip 5 (the light emitting element array chip 5 and the fixing adhesive 4 are fixed). And a recess 1a having a depth within ± 0.1 mm with respect to the total thickness.

  The substrate 1 has a large number of first circuit conductors 2 disposed on the upper surface thereof, and a plurality of light emitting element array chips 5 disposed between the lower surface and the bottom surface of the concave portion 1a in the recess 1a. The adhesive 4 is disposed and fixed, and functions as a support member for supporting them.

  If the substrate 1 is made of a glass cloth base epoxy resin or the like, the glass cloth base formed using glass fibers is impregnated with a liquid epoxy resin and cured, and then cut into a predetermined shape. It is manufactured by processing the outer shape. Next, the concave portion 1a is formed on the upper surface of the obtained substrate 1 by half dicing with a blade having a predetermined width using a dicer or the like.

  The light-emitting element array chip 5 embedded in the recess 1a has a large number of light-emitting elements 7 and connection pads 6 electrically connected to the light-emitting elements 7 on the upper surface so as to have a resolution of 300 dpi or more. The fixing adhesive 4 disposed between the bottom surface of the recess 1a and the lower surface of the light emitting element array chip 5 is fixed at a predetermined position in the recess 1a.

  The second circuit board is a circuit board in which a second circuit conductor 9 made of copper or an alloy thereof is formed on the lower surface of an insulating board made of epoxy resin or the like as the board 8, or the board 8 is flexible as an insulating material, for example. Flexible printed circuit board (FPC) produced by etching the second circuit conductor 9 on the lower surface of a flexible substrate based on a flexible polyimide resin and the copper foil bonded to the lower surface. Alternatively, a metal wiring made of gold, silver, copper, or an alloy thereof as the second circuit conductor 9 is formed on the lower surface of a transparent substrate such as a transparent glass substrate or sapphire substrate as the substrate 8 by a thick film or thin film method. The produced circuit board or the like is used.

  In the case where an insulating substrate is used as the substrate 8 of the second circuit substrate, the substrate can be manufactured independently, so that the influence at the time of forming the conductor can be eliminated. Further, when a flexible substrate is used as the substrate 8, the flexible substrate is usually in the form of a film, so that the substrate 8 can be made thin and light. Further, when a light-transmitting substrate is used as the substrate 8, since the light-transmitting substrate can be disposed on the light-emitting element 7 and used for protecting the light-emitting element 7, electrical connection and protection of the light-emitting element 7 are possible. It can also serve as.

  A number of light emitting elements 7 provided on the upper surface of the light emitting element array chip 5 are linearly arranged in the main scanning direction at a density of, for example, 600 dpi so as to have a resolution of 300 dpi or more. These light-emitting elements 7 have a structure in which a p-type semiconductor and an n-type semiconductor made of, for example, AlGaAs or GaAsP are stacked and pn-bonded to each other. When external power supply power is applied through the circuit conductor 9, the electrons are injected into the p-type semiconductor of the light-emitting element 7 and the holes are injected into the n-type semiconductor, and these are injected near the pn junction. By recombining and converting the energy generated during the recombination into light, light is emitted at a predetermined wavelength and brightness.

  The light emitting element array chip 5 employs a semiconductor manufacturing technique, specifically, MOCVD (Metal Organic Chemical Vapor Deposition) method, etc., and epitaxially grows the above compound semiconductor on the upper surface of a substrate made of single crystal GaAs or Si. After the light emitting element 7 is formed, the connection pads 6 are deposited in a predetermined pattern by a thin film forming technique.

  The connection pad 6 of the light emitting element array chip 5 mounted in the recess 1a formed on the upper surface of the substrate 1 of the first circuit board has the light emitting element array chip 5 mounted in the recess 1a. By appropriately setting the height, the upper surface of the light-emitting element array chip 5 can be made almost the same height as the first circuit conductor 2. Thus, the first circuit conductor 2 and the connection pads 6 of the light emitting element array chip 5 can be connected with high reproducibility using the second circuit board 8 having the second circuit conductor 9 formed on the lower surface. it can.

  As shown in FIG. 1, the second circuit board may cover the light emitting element array chip 5 with the substrate 8, and as shown in FIG. 2, one of the substrates 8 of the second circuit board. A through hole 10 such as a slit corresponding to the light emitting element 7 may be provided in the part. However, when the through hole 10 is provided in the substrate 8, in order to protect the light emitting element 7, the upper surface of the substrate 8 is covered with a translucent reinforcing substrate 11 such as a cover glass so as to cover the through hole 10. Is preferred.

  When the second circuit board is shaped to cover the light emitting element array chip 5 as shown in FIG. 1, it can be protected by covering the light emitting element array chip 5. As shown in FIG. 2, when a through hole 10 such as a slit corresponding to the light emitting element 7 is provided in a part of the substrate 8 of the second circuit board, the light emitted from the light emitting element 7 through the through hole 10. Therefore, light can be extracted efficiently. Furthermore, when the through-hole 10 is provided in the substrate 8, if the substrate 8 is a flexible substrate, the flexible substrate is usually a film, so that the substrate 8 can be made thin and light. .

  The second circuit conductor formed on the lower surface of the second circuit board includes the first circuit conductor 2 formed on the upper surface of the first circuit board and the connection pads 6 formed on the upper surface of the light emitting element array chip 5. When the electrical connection is made via 9, since the pitch between the connection pads 6 is small, it may be difficult to use a connection method using solder or the like. In that case, it is preferable to connect using an anisotropic conductive paste. When the second circuit conductor 9 is electrically connected to one end of the first circuit conductor 2 and the connection pad 6 using an anisotropic conductive paste, the two connected are electrically connected only in the vertical direction. Therefore, a short circuit in the lateral direction can be effectively prevented.

  In the optical printer head of the present invention, since a large number of second circuit conductors 9 are formed on the lower surface of the substrate 8 of the second circuit board, even if a disturbance such as vibration is applied, the adjacent second circuit conductors 9 are arranged. There is no problem that the circuit conductors 9 are short-circuited, and this contributes to improving the reliability of the optical printer head.

  Further, for the connection between the second circuit conductor 9 and the connection pad 6 on the upper surface of the light emitting element array chip 5, the size of the connection pad 6 is sufficient to be about several tens of μm square. 5 can be reduced in size, and an optical printer head using a large number of light emitting element array chips 5 can be reduced in size and cost.

  Thus, such an optical printer head of the present invention causes the light emitting elements 7 of the light emitting element array chip 5 to selectively emit light individually based on the image data from the outside, and the emitted light is a rod lens (not shown) or the like. And an optical printer head capable of forming an image by irradiating an external photoconductor via the optical system and forming a predetermined latent image with a high resolution of 300 dpi or more on the photoconductor.

  Then, the latent image formed on the photoreceptor becomes a toner image through a development process, and a predetermined image is recorded on the recording paper by transferring and fixing the toner image onto the recording paper. Become.

  The present invention is not limited to the embodiments described above, and various changes and improvements can be made without departing from the scope of the present invention.

  For example, in the example of the above-described embodiment, a driver IC for controlling the light emission of the light emitting element 7 may be mounted on the substrate 1.

  Furthermore, in the example of the above embodiment, the LED array head using the light emitting diode as the light emitting element 7 has been described as an example. However, other optical printer heads such as an EL head, a plasma dot head, a liquid crystal shutter head, The present invention is also applicable to fluorescent heads, PLZT heads, and the like.

It is sectional drawing which shows an example of embodiment of the optical printer head of this invention. It is sectional drawing which shows the other example of embodiment of the optical printer head of this invention. It is sectional drawing which shows the example of the conventional optical printer head. It is sectional drawing which shows the example of the conventional optical printer head. It is a principal part enlarged plan view which shows the example of the conventional optical printer head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Resin board | substrate 1a ... Recessed part 2 ... 1st circuit conductor 3 ... Insulating layer 4 ... Adhesive for fixation 5 ... Light emitting element array chip 6 ... Connection Pad 7 ... Light emitting element 8 ... Substrate of second circuit board 9 ... Second circuit conductor
10 ... Through hole (slit)
11 ... Translucent reinforcing substrate (cover glass)

Claims (5)

A plurality of first circuit conductors are provided on a resin substrate, and a plurality of light emitting elements and connection pads are provided on the upper surface of the first circuit board obtained by coating an insulating layer on the first circuit conductors. An optical printer head having a light emitting element array chip having mounted thereon and electrically connecting the first circuit conductor to the connection pad, wherein a concave portion in which the light emitting element array chip is embedded is formed on an upper surface of the substrate. The lower surface of the second circuit board formed and bonded to the bottom surface of the concave portion with an adhesive, with one end of the first circuit conductor facing the upper surface of the first circuit board An optical printer head characterized in that it is electrically connected to the connection pad via a second circuit conductor formed on the substrate. The optical printer head according to claim 1, wherein the second circuit board has the second circuit conductor formed on a lower surface of a flexible board. 3. The optical printer head according to claim 1, wherein the second circuit board has a through hole formed in a portion corresponding to the light emitting element. 2. The optical printer head according to claim 1, wherein the second circuit board has the second circuit conductor formed on a lower surface of the translucent board. 2. The optical printer head according to claim 1, wherein the second circuit conductor is electrically connected to one end of the first circuit conductor and the connection pad using an anisotropic conductive paste. .

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