JPH08106614A - Method for forming bonding pad for electric circuit by micro machining - Google Patents

Abstract

PURPOSE: To form an electric channel at a low cost by conducting a connection terminal of a surface with a bonding pad of a rear face with a conductor on a chip side face. CONSTITUTION: When dicing is performed from the rear face based on base lines 12, and 13, figure (a) is a figure viewing the rear face 14 of a substrate, and a dotted line shows a pattern of a device 5 on the surface. In figure (b), a position of a rear face conductor corresponding to a part (e.g. directly below) where no electric conductor exists between connection terminal 11 of the device 5 is diced and separated from the rear surface based on the reference line 13, and the bonding pads of all connection terminals 11 are formed on the corresponding position (e.g. just under) of the rear face. In such a case, the position of the dicing is 15. Similarly, as shown in figure (c), the rear face conductors are separated from the rear face based on the reference lines 12, 13. The lines 16, 17 show one of the positions of the dicing, and the line 18 is a groove generated by the separation of the rear face conductors shown by figure (b). Thus, by dicing in such a manner, the bonding pad positioned to the connection terminal of the device is formed on the rear face.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a bonding pad for an electric circuit formed on the front (front) surface of a substrate on the back surface of the substrate in order to produce a floating thin-film magnetic head used in, for example, a magnetic drum device. The present invention relates to a method for forming a bonding pad for an electric circuit by microfabrication, which is used in the case of doing so.

[0002]

2. Description of the Related Art As an example of an electric circuit manufactured by microfabrication,
As shown in FIG. 6, the structure of a conventional thin film magnetic recording head is a perpendicular magnetic recording head in which the head surface 6 is located at the tip of the head chip 5 and faces the sliding surface 31 of the drum, and the head surface has many chips. The magnetic recording heads are roughly classified into horizontal magnetic recording heads which are provided on planes arranged side by side and which face sliding surfaces arranged parallel to the planes. This horizontal magnetic recording head has the advantage that a high output magnetic recording head can be realized because the area occupied by the coil can be increased and the number of turns of the coil can be increased. It is necessary to pull out from the front surface of the head to the back surface opposite the head surface. FIG. 7 shows a schematic structure of a flying thin film magnetic head as an example of a horizontal head. As shown in FIG. 1A, the floating thin-film magnetic head 1 is composed of a rotating magnetic drum 2
And float at a distance of several mm. FIG. 1B is an enlarged view showing the schematic structure of the flying thin film head. The slider surface 4 of the slider 3 is on the same plane as the head surface 6 of the thin film magnetic head chip 5, and the chip on the head surface is shown. The height from the substrate surface is about several tens of μm.

[0003]

Therefore, a bonding pad is provided on the same surface where the head is formed, and the FP
When C (Flexible Printed Circuit) or wire is bonded, its height exceeds the level of the head surface 6, which may damage the surface of the magnetic drum 1 or affect the floating characteristics hydrodynamically. Inconvenience occurs. For this reason, conventionally, a head is formed on the front surface of the substrate, a through hole is formed in the substrate, an electric conductor is embedded in the head for electrical connection, and an electrode pad is formed on the back surface for bonding. However, in a highly integrated device, that is, in a device in which a large number of heads are densely integrated, the diameter of the through hole becomes small and the pitch becomes narrow, and it becomes difficult to open such a through hole. In particular, when the substrate forms part of a circuit such as a magnetic circuit, the substrate material is limited, and when the magnetic resistance must be reduced, the thickness also increases, making it more and more difficult to accurately open through holes. It gets harder. For example, if the ferrite substrate is 0.5 mm thick, the through hole diameter is 0.1 mmφ, and the pitch is 0.2 mm, it is impossible to open it by ultrasonic processing.
Although it can be opened by an excimer laser or a yag laser, the manufacturing cost becomes high because the apparatus is expensive and the throughput is small. In addition, since the thin film head is formed by a planar process (photolithography, dry etching, etc.), it is necessary to have a substrate with high precision smoothness. If the through hole is filled with silver paste, etc. In order to obtain the above, it is necessary to polish the substrate, which also increases the cost. Therefore, the above-mentioned conventional technique has a drawback that the manufacturing cost becomes high.

An object of the present invention is to provide a device having an equivalent function at a lower cost by using a method different from the conventional technique.

[0005]

In order to solve this problem, the method of the present invention is directed to a first parallel line group and a first parallel line group which are arranged on the surface of a substrate in sequence at equal intervals. Electrical conductive film formed on the back surface of the substrate in which a large number of micro electric circuits having the same pattern are formed in a large number of spaces of the same shape which are separated by a second group of parallel lines which are arranged at equal intervals. The first step of adhering to the entire surface, and the first parallel line position at the end of the first parallel line group and the second parallel line position at the end of the second parallel line group are separated by dicing In a second step, the substrate is diced from the back surface of the substrate so that the plurality of fine electric circuits are separated from each other using the first parallel line position and the second parallel line position as reference lines for dicing. A third step of forming a large number of electric circuit chips by cutting with A method for forming a bonding pad for an electric circuit by a microfabrication including a fourth step of attaching an electric conductor film having a required width from the front surface of the substrate to the conductor film on the back surface of each of the electric circuit chips. is there. In the third step, a separation groove is formed by dicing from the back surface of the substrate to the conductor film with the first or second parallel line position as a reference line for each of the plurality of micro electric circuits. The fourth step may include a step of cutting the electric conductor film having the required width at the position of the separation groove.

[0006]

According to this method, an electric channel can be formed by electrically connecting the connection terminal on the front surface and the bonding pad on the back surface with the conductor on the side surface of the chip. In this case, how to realize the separation between the channels and how to realize the alignment of the connection terminal of each channel, the bonding pad on the back surface, and the side surface conductor are problems. This method solves this problem as follows. That is, a specific position without a device pattern is cut off from the surface of the substrate by dicing with reference to the device pattern on the surface to form a reference line (substrate edge). Since this reference line can be created in a specific positional relationship with the device pattern, it can be seen from the back surface of the substrate how much distance there is just below the reference line.
Therefore, with this reference line as a reference, by making a notch by dicing in the back conductor at the position directly below the conductor-free portion between the connection terminals on the surface, it is aligned directly below the connection terminals on the surface and electrically separated. Bonding pads can be formed. Similarly, if two reference lines are used, chip separation can be performed from the back side. Next, the side conductors are attached, but the connection terminals on the front surface and the bonding pads on the back surface are not electrically connected only by attaching to the side surface of the chip, so not only the side surface
The side surface conductor is attached so as to overlap with the pattern on the back surface to some extent. Next, the side surface conductor is separated. Since the cross section of the back surface electrode separation groove previously formed can be seen on the side surface of the chip, the side surface conductors can be aligned and separated to the connection terminals and bonding pads of each channel by dicing along the groove from the side surface of the chip. At this time, if the cutting depth is larger than the overlap width, the connection terminals and the bonding pads can be separated at the same time. Further, in order to cut and separate, the connection terminals on the surface must be aligned vertically to the side surface of the chip to be cut and have parallel straight portions having a length equal to or longer than the cut length from the side surface. Further, before dicing, it is necessary to attach a back surface conductor which becomes an electroplated conductor of a bonding pad.

[0007]

EXAMPLE FIG. 1 shows a method of forming a dicing reference line by this method. (A) shows an example of a dicing apparatus used in this method, 7 is a dicing blade, and 9 is a jig for fixing the substrate 8. A desired position can be cut by aligning the pattern formed on the substrate 8 and the blade position while looking from above.
(B) shows how to make a reference line by this method, and 10 shows a device pattern formed on the surface of the substrate, for example, a large number of identical devices having the pattern of the thin film magnetic head chip (device) 5 are formed. I am doing it. Reference numeral 11 represents an electrical connection terminal in one device 5. 1
Reference numeral 2 denotes a cutting position that serves as a dicing reference line of the present method. An appropriate position outside the endmost device 5 (for example, a portion corresponding to a chip edge) is cut by dicing, and a cut edge generated thereby is used as a reference. Make a line. (C) shows the cut position for making the other dicing reference line 13, which is made by cutting an appropriate position outside the device 5 at the end in the direction orthogonal to the reference line 12. (D) shows the finished product. The cut edge thus formed has a specific known positional relationship with the pattern formed on the front surface. Therefore, when the cut edge is used as the dicing reference lines 12 and 13 in the dicing from the back surface of the substrate 8, the front surface It is possible to accurately separate the devices 5 formed in the above.

FIG. 2 shows a method of performing dicing from the back surface based on these reference lines 12 and 13.
1A is a view of the back surface 14 of the substrate shown in FIG. 1C, and the dotted line shows the pattern of the device 5 on the front surface. As shown in (b), a portion between the connection terminals 11 of the device 5 without an electric conductor (for example, directly below)
The positions of the back surface conductors corresponding to are separated by dicing from the back surface based on the reference line 13, and all the connection terminals 1
One bonding pad is formed on the back surface at a corresponding position (eg, directly below). Reference numeral 15 indicates one of the dyne sig positions in this case. Similarly, as shown in (c), the reference line 1
Chips 2 and 13 are separated from the back surface with reference lines 2 and 13. 1
Reference numerals 6 and 17 indicate one of the dicing positions. Reference numeral 18 denotes a groove formed by the back surface conductor separation shown in (b). Therefore, if the dicing is performed in this manner, the bonding pads aligned with the connection terminals of the device can be formed on the back surface, and if the substrate is attached to the dicing sheet and the dicing is performed, the dicing sheet does not need to be reattached. , Can be separated into chips.

After separation into chips, an electric conductor is attached to the side surface of the chip. FIG. 3 shows an example of attaching the conductor by oblique vapor deposition. Reference numeral 5 is a separated device chip, and 20 is a spacer for standing and arranging the chips 5 on the jig 19, and has a groove for accommodating the head portion 6 of the chip 5. As shown in FIGS. 3A and 3B, the length of the spacer 20 is somewhat shorter than the length of the chip 5, and the connection terminal 11 is arranged so as to protrude from the spacer 20. Reference numerals 21 and 22 denote flows of vapor deposition particles. As shown in (a) and (b), the vapor deposition is performed twice from the diagonal left direction and the diagonal right direction, so that the connection terminal 11 and the left side surface of the chip 5, And forming a good electrical connection between the right side of the chip 5 and the bonding pad (not shown). Although this example shows a method by oblique vapor deposition, it can also be formed by sputtering, plating, or Ag paste coating.

After the electric conductor is attached to the side surface of the chip 5, the side surface conductor is separated. FIG. 4 shows the method. As shown in (a), the chips 5 to which the side surface conductors 23 are attached are arranged as shown in the figure through a dicing spacer 26 having a groove for accommodating the head portion of the chip 5, and fixed to a dicing jig 25. Then, a cut is made from the side surface of the chip 5 with a dicing blade 7. The length of the spacer 26 is shorter than the length of the chip 5 by at least the cut depth. FIG. 2B is a view seen from above. Since the plurality of chips 5 are arranged by vertically arranging them on the contact surface 30 of the jig having good parallelism, the separation of the back surface conductors shown in FIG. The cross-sections of the grooves 18 can be seen in a straight line. Therefore, it is possible to perform dicing along this straight line and cut a large number of chips at once. 27 shows one of the dicing positions.

FIG. 5 (a) is a view seen from the surface of the completed chip 5, and 28 is a groove formed by cut dicing, which is cut to a width greater than the width of the side surface attached conductor 23. Are separated. (B)
Is a view of the completed chip as seen from the back surface, and the chip is cut into a width greater than the width of the side surface attached conductor 23.
9 are electrically separated. 6 is a head portion, and 18 is a back surface conductor separation groove.

[0012]

As described in detail above, according to the method of the present invention, in a device in which it is necessary to form the bonding pad of the electric circuit formed on the front surface on the back surface,
It can be formed at a lower cost than the conventional through-hole method.

[Brief description of drawings]

FIG. 1 is a sectional view (a) and a plan view (b) for explaining a process of creating a reference line by dicing in the method of the present invention.
(C) and (d).

FIG. 2 is a plan view for explaining formation of a back surface conductor and chip separation in the method of the present invention.

FIG. 3 is a cross-sectional view for explaining adhesion of a side conductor in the method of the present invention.

FIG. 4 is a side view (a) and a plan view (b) for explaining side conductor separation in the method of the present invention.

FIG. 5 is a front view (a) and a rear view (b) for explaining side conductor separation in the method of the present invention.

FIG. 6 is a schematic perspective view showing an example of a conventional perpendicular magnetic recording head.

FIG. 7 is a side view (a) and a perspective view (b) showing an example of a conventional horizontal magnetic recording head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flying type thin film magnetic head 2 Magnetic drum 3 Slider 4 Slider surface 5 Thin film magnetic head chip (device) 6 Head surface 7 Dicing blade 8 Substrate 9 Jig 10 Pattern on substrate surface 11 Device connection terminal 12 Dicing reference line 13 Dicing Reference line 14 Substrate back surface 15 Dicing position 16 Dicing position (first parallel line group) 17 Dicing position (second parallel line group) 18 Back surface conductor separation groove 19 Jig 20 Deposition spacer 21,22 Deposition particle flow 23 Side conductor 24 Cross Section of Back Surface Conductor Separation Groove 25 Jig 26 Dicing Spacer 27 Dicing Position 28 Cut Groove 29 Bonding Pad 30 Jig Attaching Surface 31 Sliding Surface

Claims (2)

[Claims] 1. A first parallel line group sequentially arranged at equal intervals on a surface of a substrate and a second parallel line intersecting the first parallel line group at a predetermined angle and sequentially arranged at equal intervals. A first step of depositing an electric conductor film on the entire surface of the back surface of the substrate on which a large number of micro electric circuits of the same pattern are formed in a large number of spaces of the same shape divided by line groups; A second step of separating the first parallel line position of the end of the line group and the second parallel line position of the end of the second parallel line group by dicing, the substrate, the first parallel line A third step of forming a large number of electric circuit chips by dicing the back surface of the substrate by dicing so that the plurality of fine electric circuits are mutually separated by using the position and the second parallel line position as a reference line for dicing. , The surface of the substrate for each of the plurality of electrical circuit chips A fourth step of adhering an electric conductor film having a required width to the conductor film on the back surface from the fourth step. 2. In the third step, a separation groove is formed by dicing from the back surface of the substrate to the conductor film with the first or second parallel line position as a reference line for each of the plurality of fine electric circuits. 2. The microfabrication electricity according to claim 1, further comprising a step of forming an incision at the position of the separation groove in the electric conductor film having the required width in the fourth step. Method of forming bonding pad for circuit.