JP2879773B2 - IMAGE DEVICE AND ITS MANUFACTURING METHOD - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image device using an image array, such as an LED head, a contact type image sensor, and a liquid crystal shutter array head.

[0002]

2. Description of the Related Art In an image device such as an LED head, a liquid crystal shutter array head, and a contact image sensor, an image array such as an LED array or a liquid crystal shutter array is mounted on a substrate and connected to substrate wiring. For the substrate wiring, a deposited film of Al or the like is usually used, and for the substrate, a glass substrate having excellent surface smoothness is used.

However, a vapor-deposited film has low adhesion strength to a substrate, requires a long time for film formation, and is poor in mass productivity. For example, in vapor deposition, the degree of vacuum is obtained by evacuation for each film formation, and then the substrate wiring is vapor-deposited and taken out. This requires a long time for one film formation, and requires a large-scale vapor deposition apparatus.

The use of a monocular lens in an image apparatus has been studied, but in this case, the alignment between the monocular lens and the substrate is crucial. If the accuracy of the alignment is low, or if the alignment is incorrect due to thermal expansion or the like, white streaks or black streaks are generated in the stamp image or the read image. Therefore, the alignment between the substrate and the monocular lens is performed inexpensively and reliably.
In addition, it is necessary to prevent misalignment due to thermal expansion or the like.

Further, in an image apparatus, it is also known that an image array is flip-chip connected to substrate wiring. However, soldering cannot be performed with Al wiring, and the electrode bumps provided on the array and the Al wiring are thermocompression bonded. . Thermocompression requires high pressure and can damage fragile image arrays.

[0006]

The basic objects of the present invention are: 1) to provide a substrate and a monocular lens array at a low cost; 2) to accurately position the substrate and the monocular lens, and to eliminate misalignment due to thermal expansion and the like. 3) Flip chip connection between the image array and the substrate wiring is facilitated. 4) Improving the adhesion strength of the substrate wiring to the substrate and the flip chip connection strength of the image array. This is to improve the quality (claim 1). Another object of the present invention is to reduce the density of substrate wiring.

[0007]

According to the image apparatus of the present invention, an image array provided with a large number of light receiving / emitting elements is arranged in rows on a first main surface of a transparent plastic substrate, and a substrate is provided on the other main surface. A monocular lens is provided in an array integrally with the first main surface, and a portion facing the light receiving and emitting element is made a smooth surface on the first main surface;
An electrode bump of the image array is flip-chip connected to a substrate wiring provided on a roughened area in which the other area is roughened.

If the substrate is a transparent plastic substrate and the monocular lens is integrally formed, the monocular lens and the substrate can be formed at low cost. In addition, since the monocular lens is integrated with the substrate from the beginning, there is no need to align the two, and there is no misalignment due to thermal expansion or the like. As a result, problems such as generation of white streaks and black streaks can be solved from the beginning.
The substrate is roughened by sandblasting, etching, or the like in order to increase the adhesion to the substrate wiring. The region to be roughened is a portion of the image array other than the light emitting and receiving elements, and this region is entirely or partially roughened. As a result, the substrate wiring can be firmly adhered to the roughened area of the plastic substrate. Since there is a monocular lens on the back surface of the substrate, the image array is limited to flip-chip connection, and flip-chip connection can be easily made by using a copper plating film or a solder plating film for the substrate wiring. Here, since the portion facing the light emitting and receiving element is a smooth surface, an optical path to the light emitting and receiving element is secured, and since the other surface is rough, unnecessary light is scattered by the rough surface and the image quality is improved. Further, by using the rough surface, the adhesive force of the substrate wiring to the substrate and the strength of flip-chip connection are improved.

Preferably, the wiring of the substrate is formed by laminating a plating film of a conductor on a plating film of a metal underlayer, and the metal underlayer secures adhesion to the substrate and the conductive film secures the conductivity. For example, an electroless plating film of Ni, Cr, Ti or the like is used as the metal base film, and a copper film or a solder film is used as the conductor plating film. Now, if there is solder plating on the substrate wiring at the flip chip connection part, flip chip connection with the electrode bumps of the image array can be realized by soldering. As a result, the problem of damage to the image array due to the pressure during thermocompression is eliminated, and flip-chip connection can be easily performed in a shorter time as compared with thermocompression in an electric furnace while applying pressure. The solder plating film may be partially provided by plating only the flip chip connection portion on the conductor film made of a copper plating film. However, if the entire conductor film is made of a solder plating film, the number of steps is reduced.

Preferably, the substrate wiring comprises a first substrate wiring provided on one side of a column of the image array and a second substrate wiring provided on the other side of the column. As a wiring that is folded and folded in a substantially U shape for every two image arrays, the corresponding light receiving and emitting elements of the two image arrays are electrically connected to each other within the divided wiring, Is provided with a first back surface wiring and a second back surface wiring on both outer sides of a region where a monocular lens is provided, and a first substrate wiring and a first back surface wiring are provided.
Are connected to each other in a predetermined order, and the second substrate wiring and the second rear surface wiring are connected to each other by through holes. , The divided second substrate wirings are electrically connected to each other in a predetermined order. In this case, the density of the substrate wiring is reduced to half, and it becomes easy to provide the substrate wiring composed of a large number of individual wirings by plating. Although there is a limit in high-density wiring in film formation by plating, the problem can be solved by dividing the substrate wiring into two.

For example, when the total number of individual wirings is 64, two substrate wirings, for example, 32 wirings are provided on both sides of the columns of the image array. Since the substrate wiring has a substantially U-shape and both ends are flip-chip connected to the electrode bumps of the image array, both ends are isolated without being connected to other parts. Therefore, a through hole is provided in the plastic substrate, the through hole, the backside wiring of the substrate, the next U-shaped substrate wiring are connected in this order, and the divided substrate wirings are connected to each other. The through-hole occupies the largest area in processing the substrate and is the limit of mounting. According to the fourth aspect of the present invention, the substrate wiring is provided on both sides of the image array, and the back wiring is performed in units of two arrays. Therefore, the substrate wiring is provided only on one side of the column of the image array and the back wiring is connected to the matrix. In comparison, the through hole density can be reduced to 1/4. For this reason, through hole processing becomes extremely easy.

Such an image apparatus includes, for example, a step of integrally molding a substrate and a monocular lens with plastic, a step of partially roughening a main surface of the substrate opposite to the side on which the monocular lens is provided, It is manufactured by a step of plating a metal base film on a main surface of a roughened substrate, a step of plating a conductor film on a metal base film soil, and a step of flip-chip connecting an image array on the conductor film. . Here, preferably, the conductor film is formed as a solder plating film at the flip chip connection portion, and the vicinity of the electrode bump is locally heated and soldered from the lens side with laser light or infrared light. In this way, flip-chip connection can be achieved, for example, only by scanning with a laser or by heating with infrared rays.

[0013]

1 to 5 show an embodiment. In FIG.
Reference numeral 2 denotes a plastic substrate, which uses a transparent plastic substrate such as epoxy, acrylic, or polycarbonate.
Reference numeral 4 denotes a monocular lens which is formed in an array, and is provided, for example, for each LED array 6. The monocular lens 4 is formed integrally with the plastic substrate 2. Reference numeral 6 denotes an LED array in which, for example, about 40 LED arrays are arranged in a straight line along the first main surface of the substrate 2.
In addition to the ED array 6, a MOSCCD array or the like may be used. A substrate wiring 8 is provided on the first main surface of the substrate 2 and an LED is provided.
The electrode bumps 10 connected to the electrodes of the array 6 are flip-chip connected. Reference numeral 12 denotes a clip terminal.
And to, for example, the main surface on the opposite side of the substrate 2. As a method of connecting the common electrode of the LED array 6, any method other than the method using the clip terminal 12 can be used.

FIG. 2 shows the substrate 2 viewed from the monocular lens 4 side.
The following shows the arrangement. Assuming that the number of light emitters of the LED array 6 is 64, the substrate wiring 8 has 64 individual wirings 8-1 to 8-6.
The individual wirings 8-1 to 8-32 are arranged on the upper side in the figure, and the individual wirings 8-33 to 8-64 are arranged on the lower side in the figure. Each of the individual wirings 8-1 to 8-64 is substantially U-shaped,
The LED array 6 is divided and provided for every two. Board wiring 8
Is divided into a first substrate wiring composed of individual wirings 8-1 to 8-32 and a second substrate wiring composed of individual wirings 8-33 to 8-64. To be provided. The individual wirings 8-1 to 8-64 are two electrode bumps 1
Since the portion between 0 and 10 is folded in a U-shape and is not connected to the other on the first main surface, a through hole 14 is provided to
Are connected to each other via the back surface. 16 is through hole 1
In the row of 4, the arrangement pitch of the through holes 14 is 0.8 m.
Since about m is required, the rows of through holes 16 are arranged in two rows and obliquely to the longitudinal direction of the substrate 2. A back surface wiring 20 is provided on the back surface (main surface on the side of the monocular lens 4) of the plastic substrate 2, and the substrate wiring 8 is provided through a through hole 14.
Connect with In this manner, the substrate wiring 8 divided for every two LED arrays 6 is divided into a row of through holes 16 and a rear wiring 2.
Interconnected through a row of 0 and next through holes 16.

FIG. 3 shows a flip chip connection portion, and FIG.
Shows the state immediately before connection as viewed from the side. LED array 6
Is composed of a semiconductor substrate such as GaAs. Reference numeral 22 in FIG. Reference numeral 24 denotes an electrode of the LED array 6 provided by etching, for example, an Al film, and the electrode bump 10 is laminated on the Al electrode 24 in the flip chip connection portion. Turning to FIG. 4, the electrode bump 1
Numeral 0 is a film in which a film of Au, Au-Pd, Pd or the like is laminated on a metal base film of Ni, Cr or Ti, etc. Here, a Ni plating layer 26 is used as the metal base film, and A
The u plating layer 28 was laminated.

On the plastic substrate 2 side, Ni, Cr, T
A solder plating layer 32 was laminated on the metal base film 30 of i or the like to form individual wirings 8-1 to 8-64. Metal underlayer 30
Is formed by, for example, electroless plating of Ni, and unnecessary portions are removed by etching or lift-off. Metal underlayer 3
The thickness of 0 is preferably, for example, about 2 to 3 μm. The solder plating layer 32 is formed by immersing the substrate 2 in a solder bath, and has a thickness of, for example, 1 to 100 μm, and preferably about 5 to 20 μm. If the film thickness is larger than this, the adhesive force to the substrate 2 decreases, and if it is too thin, soldering to the electrode bumps 10 becomes difficult. Numeral 34 denotes a roughened portion, which is formed by roughening the front and back surfaces of the substrate 2 by sandblasting, etching or the like, except for a portion facing the light emitting body 22 and a surface portion of the monocular lens 4. The degree of roughening is, for example, about 0.1 to 5 μm, preferably 0.3 to 5 μm as an average surface roughness measured by a surface roughness meter.
If the roughness is made larger than about 3 μm, the mounting accuracy of the LED array 6 is affected.
The adhesive strength of 0 decreases. Although not particularly shown in FIG. 4, the back wiring 20 is also formed by laminating a metal base film 30 and a solder plating layer 32 after roughening the surface of the substrate 2.
The reason for using the solder plating layer 32 is to facilitate soldering with the electrode bumps 10. Therefore, for example, a copper plating layer is used instead of the solder plating layer 32, and the electrode bump 10
Cream solder or the like may be applied to a portion to be connected with the flip chip. However, according to the embodiment, the application of the cream solder becomes unnecessary, and the danger that the individual wirings 8-1 to 8-64 are short-circuited by the applied cream solder is eliminated.

FIG. 5 shows the steps up to the flip chip connection of the LED array 6. The substrate 2 and the monocular lens 4 are integrally molded using a plastic such as polycarbonate, epoxy or acrylic. Next, the portion facing the light emitter 22 and the surface of the monocular lens 4 are masked,
The substrate is roughened by sandblasting or etching. Thus, a roughened region 34 is formed. Before and after the formation of the roughened region 34, the substrate 2 is perforated, then the substrate 2 is immersed in a Ni plating solution, and Ni plating is performed by electroless plating. Subsequently, unnecessary portions are etched to form a metal base film 30. Thereafter, the substrate 2 is immersed in the molten solder so that the solder is deposited only on the metal base film 30,
In particular, the solder plating layer 32 is obtained without performing patterning. After these, through-hole processing is performed,
0 and the substrate wiring 8 are connected.

After the wirings 8 and 20 are formed, the LED array 6 is mounted and temporarily fixed using the clip terminals 12. It is preferable that the clip terminal 12 has such an elasticity that it can be temporarily fixed. Next, using the semiconductor lasers 40, 40 and the like in FIG. 5, visible light and infrared light are irradiated from the side of the monocular lens 4 to melt the solder plating layer 32 and solder it to the electrode bumps 10. Since the solder does not directly adhere to the surface of the plastic substrate 2 but only to the portion where the metal base film 30 is present, even if the solder plating layer 32 is melted, the individual wirings 8-1 to 8-1
There is no danger of 8-64 shorting.

In this way, the flip chip connection can be performed by soldering, and the lasers 40, 40
Flip-chip connection can be performed only by scanning the back surface of the substrate. Unlike the thermocompression bonding of Al to the substrate wiring, the soldering only needs to be performed with a small pressure from the clip terminal 12, and there is no possibility that the fragile GaAs substrate of the LED array 6 is broken. Furthermore, since it is locally heated by light, the plastic substrate 2 and the monocular lens 4 are deformed,
There is no melting of the solder plating layer 32 other than the flip chip connection part. Therefore, there is no problem even with the plastic substrate 2 having low heat resistance or the solder plating layer 32 having low melting point, and it is not necessary to pass through the reflow furnace, so that the time required for soldering is short, and the flux in the solder is reduced by the LED in the reflow furnace.
There is no problem such as attachment to the array 6.

Although it is preferable to use the laser 40 to locally heat only the flip chip connection portion, infrared heating using a normal light source may be used as long as the entire heating by the reflow furnace or the contamination by the flux is only avoided. . FIG. 6 shows such an example. In the figure, reference numeral 42 denotes an infrared lamp, and 44 denotes a parabolic reflector having a cross section. The light from the infrared lamp 42 is converted into parallel rays by the reflector 44, and LE
Only the back surface of the D array 6 is locally heated.

The operation of the embodiment will be described. The basic concept of the embodiment is that the substrate 2 and the monocular lens 4 are integrated. This is achieved by performing integral molding using the plastic substrate 2. As a result, the alignment between the substrate 2 and the monocular lens 4 is performed at the time of molding, and the problem of misalignment due to thermal expansion or the like due to a change in ambient temperature is also solved. The LED array 6 is aligned with the substrate wiring 8 and the monocular lens 4
Is integrated with the substrate 2, the LED array 6 is aligned with the monocular lens 4 via the substrate wiring 8.

The next concept of the embodiment is that a plating film is used for the substrate wiring 8 to eliminate the need for vacuum deposition of Al or the like.
As a result, mass productivity of the image device is greatly improved. The plastic substrate 2 has a better affinity with the metal base film 30 than the glass substrate, and the portions where the substrate wiring 8 and the rear surface wiring 20 are provided are roughened so that the wirings 8 and 20 and the substrate 2 are roughened.
To further improve the adhesion. Although the solder plating layer 32 alone does not adhere to the substrate 2, the solder plating layer 32 can be easily formed by providing the metal base film 30 in the middle.

The substrate wiring 8 formed by plating is not suitable for increasing the density as compared with the Al wiring formed by vacuum evaporation. Therefore, the individual wiring 8 provided with the substrate wiring 8 above the LED array 6
-1 to 8-32 and a second substrate wiring provided below the individual wirings 8-33 to 8-64, and the wiring density is reduced to half. . The individual wirings 8-1 to 8-64 have a substantially U-shaped shape, and both ends are LE
Flip chip connection was made to the electrode bumps 10 of the D array 6. This is a shape suitable for flip chip connection. In this case, the individual wirings 8-1 to 8-64 are isolated for every two LED arrays 6, so that the individual wirings 8-1 to 8-64 are connected to each other using the through holes 14 and the back wirings 20. And it is easy to provide the through hole 14 in the plastic substrate 2,
The back wiring 20 can be formed simultaneously with the substrate wiring 8 by the same process.

In the embodiment, the LED head is shown. However, the present invention is not limited to this. For example, an image sensor can be used to constitute an image device.

[0025]

According to the first aspect of the present invention, 1) the substrate and the monocular lens array are made of plastic at low cost, and 2) the substrate and the monocular lens are accurately positioned by integral molding, and are positioned by thermal expansion or the like. 3) Flip-chip connection between the image array and the board wiring is facilitated. 4) Improving the adhesion strength of the board wiring to the board and the flip-chip connection strength of the image array. 5) Reducing unnecessary light. Cut off to improve image quality. Further, 6) the density of the substrate wiring is reduced, the formation of the substrate wiring is facilitated, and the application to a high-resolution image device is facilitated. Further, since a plastic substrate is used, it is easy to provide a through-hole, and the substrate wiring divided using the back wiring is connected.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an image apparatus according to an embodiment.

FIG. 2 is a rear view of a main part of the image apparatus according to the embodiment.

FIG. 3 is a diagram showing a flip-chip connecting portion of the image device in the embodiment.

FIG. 4 is an essential part cross-sectional view showing a flip chip connection part of the image device in the embodiment.

FIG. 5 is a cross-sectional view of a main part showing flip-chip connection by laser light in the image device of the embodiment.

FIG. 6 is a diagram showing an infrared light source according to a modification.

[Explanation of symbols]

 Reference Signs List 2 plastic substrate 4 monocular lens 6 LED array 8 substrate wiring 8-1 to 8-64 individual wiring 10 electrode bump 12 clip terminal 14 through hole 16 through hole row 20 back wiring 22 light emitter 24 electrode 26 Ni plating layer 28 Au plating Layer 30 Metal base film 32 Solder plating layer 34 Roughened area 40 Semiconductor laser 42 Infrared lamp 44 Reflector

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI H01L 33/00 H04N 5/335 (58) Fields investigated (Int.Cl. ⁶ , DB name) B41J 2/44 B41J 2/45 B41J 2/455 G02B 27/00 H01L 33/00 H04N 5/335

Claims (2)

(57) [Claims] A first main surface of the transparent plastic substrate,
An image array provided with a large number of light emitting and receiving elements is arranged in a row, and a monocular lens is provided in an array with the substrate on the other main surface, and the first main surface is opposed to the light receiving and emitting element. An image device, characterized in that an electrode bump provided on the image array is flip-chip connected to a substrate wiring provided on a roughened region in which a portion is a smooth surface and the other region is roughened. 2. The substrate wiring comprises a first substrate wiring provided on one side of a column of the image array and a second substrate wiring provided on the other side of the column. As a divided wiring that is folded back in a substantially U-shape every two image arrays, the corresponding light receiving and emitting elements of the two image arrays are electrically connected to each other within the divided wiring. Is on both sides of the area where the monocular lens is provided,
By providing a first backside wiring and a second backside wiring and connecting the first substrate wiring and the first backside wiring with through holes, the divided first substrate wirings can be arranged in a predetermined order. By electrically connecting each other and connecting the second substrate wiring and the second back wiring with through holes,
The image apparatus according to claim 1, wherein the divided second substrate wirings are electrically connected to each other in a predetermined order.