JP2645235B2 - Wire bonding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a wire bonding method. In particular, there is less contact between wires when wiring between high-density connection terminals facing each other through steps such as thermal printing heads used for facsimile and contact type image sensors used for financial equipment etc. Also, the present invention relates to a wire bonding method capable of easily repairing a contact and wiring a connection terminal having a step with high reliability.

[0002]

2. Description of the Related Art A thermal printing head used for a facsimile, for example, will be described with reference to FIGS.

That is, a plurality of heating resistors 1 arranged in a line at a high density on a ceramic or other insulating substrate by a thin film technique or a thick film technique, and a heating resistor driving integration comprising a shift register, a transistor drive and a selector. A common electrode 3 to which a circuit (hereinafter referred to as an integrated circuit) 2 and one end 10 of each heating resistor 1 are connected in common; and an input signal group 4 for selectively energizing and heating each heating resistor 1 via the integrated circuit 2. The first connection terminal group 11 from each heating resistor 1 is selectively connected to the second connection terminal group 2 from the integrated circuit 2.
1, and the connection terminals are connected by wire bonding.

As for the number of connection terminals of the second connection terminal group 21, it is generally said that 32 connection terminals per 21 integrated circuits are economically superior. Accordingly, the second group of connection terminals 2 from the integrated circuit 2 is generated in units of 32 heating resistors 1.
1 will be connected. In the figure, 5 is an integrated circuit 2
An output signal terminal 6 is a power supply to the integrated circuit 2.

The facsimile recording by the thermal printing head having such a structure is performed by a predetermined heating resistor 1.
Is selectively energized to generate heat, a heat transfer film is brought into contact with the heat generating resistor 1, and is transferred to plain paper via the heat transfer film.

This state will be described with reference to FIG. 2. A resistance board 40 made of ceramic or the like in which the heating resistors 1 are arranged at high density in a direction perpendicular to the paper surface, a drive board 411 on which the integrated circuit 2 is disposed, and a common electrode 3 and the common electrode substrate 412 arranged are fixedly mounted on the heat sink 42 made of metal such as aluminum.

A heat transfer film 43 coated with a heat-softening ink and plain paper 44 are disposed on the heating resistor 1 between the heating resistor 1 and a platen roller 45 which is slidably pressed against the heating resistor 1. The platen roller 45 is inserted
The rotation of the arrow 451 causes the thermal transfer film 43 and the plain paper 44 to move in the direction of the arrow 50 together.
In the drawing, reference numerals 461 and 462 denote auxiliary rollers for supporting the movement of the thermal transfer film 43.

The thermal printing head is connected to the first connecting terminal group 11 from the heating resistor 1 and the second connecting terminal group 21 from the output of the integrated circuit 2 to the wire 47 and the heating resistor 1. A wire 48 connecting the one end 10 to the common electrode 3 and a wire 49 connecting the integrated circuit 2 to the input signal group 4 constitute a circuit as shown in FIG.

With this structure, when "slack" or "wrinkle" occurs in the thermal transfer film 43 between the auxiliary rollers 461 and 462, the heat generating resistor 1 passes through the thermal transfer film 43 from the plain paper 4 through the thermal transfer film 43.
The recording position on the recording medium 4 is shifted, the heat of the heating resistor 1 is not uniformly conducted, and not only the resolution of the recorded image is deteriorated, but also the delicate recording cannot be performed.
It is desirable that the distance l between 61 and 462 be as small as possible.

As a result, a step h is formed between the resistance substrate 40 and the drive substrate 411 and the common electrode substrate 412 as shown in FIG.
Japanese Patent Application Laid-Open No. 54-139558 discloses a technique for reducing the distance l.

According to this publication, when the step h is about 0.3 mm, the connection between the steps h can be made by the ordinary wire bonding method, but at this size, the distance between the auxiliary rollers 461 and 462 is large. The effect of reducing l can hardly be expected. That is, the thickness of the integrated circuit 2 is usually 0.3 to 0.5 mm. For this reason, the step h needs to be 0.5 to 1.5 mm.

Next, the main parts of FIGS. 1 and 2 will be described with reference to FIG.

That is, a first connection terminal group 11 in which connection terminals 111 and 112 are arranged in a staggered manner at ends of lead wires from a heating resistor on a resistance substrate 40, and an integrated circuit 2 on a drive substrate 41. Output connection terminals 211,.
The second connecting terminal group 21 arranged in a zigzag pattern is arranged to face each other via a step h, and the first connecting terminal group 11 and the second connecting terminal group 21 The near ones 111 and 211 and the far ones 112 and 212 are connected by wires 471 and 472, respectively, according to the prior art.

In this case, the resistance substrate 40 and the drive substrate 41
Are on the same plane or have a step corresponding to the thickness of the integrated circuit 2, and wire bonding is performed from the higher side to the lower side. At this time, the first connection terminal group 11 and the second connection terminal group
As a connection method of the first connection terminal group 21, the short-distance connection between the first connection terminal group 11 and the second connection terminal group 21, ie, 111 and 211, and the long-distance connection between the second connection terminal group 21 and 212 are connected, and the height of the short-distance wire 471 is increased. The wire bonding method of arranging the wire lower than the height of the wire 472 at a long distance is disclosed in
No. 65272 discloses this.

However, this wire bonding method is based on an experiment conducted by the present inventors using an ultrasonic bonder of a full-auto bonder {Shinkawa Co., Ltd., model name SWB-FA-UTC-7} using a gold wire having a diameter of 30 μm. The size of the step is equal to the thickness of the integrated circuit 2, that is, the step is 0.5 mm even if it is useful in the range of 0.3 to 0.5 mm and the wire length is 2 mm or less.
As described above, when the wire length is 2 mm or more, as shown in FIG. 3, 20 μm to 30 μm in the high step portion of the short-distance wire 471 and the long-distance wire 472.
In the extreme case, the wires 471, 4 are connected as shown in FIG.
Some were in contact with 72.

Also, as shown in FIG.
Some of them showed a bend to the bottom.
Particularly easy to contact is wire 471 comrade or wire 4
Of course, it occurs between the wires 471 and 472 that are closer together than the 72 comrades. This is because, in the case of a full-auto bonder, a wire having a large elongation rate (7 to 10% at room temperature) is used as a measure against wire breakage during bonding, so the wire is stretched at a high speed and then contracted.
It is considered that the degree of freedom for maintaining the stability as a wire loop is only in the direction perpendicular to the stretched wire, and the wire may fall down. Further, the wire falling during the experiment was unidirectional in one integrated circuit, and the contact position between the wires 471 and 472 was almost at the center of the wire. Further, as shown in FIG. 3B, after bonding the short-distance wire 471, the bonding of the long-distance wire 472 is attempted. When the cabillary 51 descends, the tip or side end of the cabillary 51 contacts the wire 471. In addition, the wire stepping phenomenon due to the cavities 51 is observed, and the wire 471 may be deformed like 471 '.

This is because, when bonding a step having a step of 0.5 mm or more, a wire tension which determines a wire loop shape (usually adopts a friction method for sandwiching a wire).
The wire 471 is bonded to the connection terminal 211, which is the first connection point, and is deformed in the direction of the arrow because it becomes longer during bonding to the connection terminal 111, which is the next connection point. Since the connection terminal 211 is deformed outwardly, the phenomenon that the wire 471 is stepped on when the cabillary 51 descends when the wire 472 is bonded next to the connection terminal 212 as the first connection point appears.

This phenomenon is caused by short-range connection terminals 111.
, 211, and the distance OSL between the bonding positions of the connection terminals 112, 212 at long distances are inappropriate, especially when the h / ISL ratio is large. Confirmed experimentally.

[0019]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned inconveniences, and a wire bonding method between connection terminal groups having steps which can reduce contact accidents between wires and achieve high density. It is intended to provide.

[0020]

That is, according to the present invention, there is provided a method of bonding a wire between a pair of corresponding connection terminals of a first connection terminal group and a second connection terminal group provided so as to face each other with a step. In the wire bonding method, the first connection terminal group
And the second connection terminal group are short-distance and long-distance, respectively.
The connection terminal pairs of the comrades are arranged in a staggered manner corresponding to each other, and
Short distance the level difference between the first connection terminal group and the second connecting terminal groups h, of the first connection terminal group and the second connecting terminal groups
The distance between the bonding positions of the connection terminal pairs of the competitors is IS
L, distance between bonding positions of connection terminal pairs at long distances
A wire bonding method , wherein h / ISL and h / OSL are both 0.4 to 0.6 , where h / ISL> h / OSL, when the separation is OSL. It is.

In this relation, the first connection terminal group and the second connection terminal group are further arranged in a zigzag pattern, and the short-distance and long-distance connection terminal pairs are made to correspond to each other. Assuming that the distance between the bonding positions of the connection terminal pair is ISL and the distance between the bonding positions of the long distance connection terminal pairs is OSL, h / ISL = 0.50 to 0.60 and h / OSL = 0.40 to 0. .45, and the step h is in the range of 1.5 to 1.5 mm.
It mm in the range of, wire bonding before the lower step side is <br/> the embodiment that after the high step side.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a thermal printing head, since the number of heat generating resistors is extremely large, about several thousands as described above, the drive circuits are integrated to reduce external peripheral circuits. In this case, the problem is several thousand
The point is how to connect the large number of heating resistors and the output of the integrated circuit and the heating resistor and the common electrode with high work efficiency and high reliability, and how to easily repair wire collapse during bonding. .

In this regard, the inventors further have a first connection terminal group and a second connection terminal group provided so as to face each other via a step.
After conducting various experiments and studies on the wire bonding method of connecting the corresponding connection terminal pairs of the connection terminal groups by wire bonding, the wire becomes longer as the step becomes larger. Since it is necessary to reduce the length of the wire as compared with the case where the length is short and it is necessary to prevent the slack of the wire, it has been found that the slack of the wire is eliminated by optimizing the ratio between the step and the bonding position.

In this case, if the size of the step is 0.5 mm or less, the wire bonding method according to the prior art is possible. However, if the step is 0.5 mm or more, there is the above-mentioned problem, and the step is 1.5 mm or more. Becomes longer, the tensile force acts on the bonding position between the first bonded wire and the connection electrode during bonding, increasing the risk of peeling, and at the same time, the bending inherent in the wire (usually referred to as curl phenomenon). Occurs and the contact with adjacent wires increases, which is not suitable for high-density wiring having, for example, nine connection terminals per 1 mm. Therefore, the range of the step in the wire bonding method of the present invention is optimally 0.5 mm to 1.5 mm. Also, when bonding the wire with the high step first, when bonding the low step, especially when using gold or aluminum wire, a tensile force acts on the neck of the wire immediately above the bonding part, and extreme In this case, there is a risk that the bonding position may be peeled off, and it is preferable that the side with the lower step is bonded first because of the constraint that the distance between the auxiliary rollers of the product to which the bonding is applied is reduced.

Next, one embodiment of the wire bonding method of the present invention will be described with reference to FIG. However, the same reference numerals as those in FIG. 3 indicate the same parts.

That is, a lead wire connected to a plurality of heating resistors (not shown) is provided at its tip with a resistance board 40 provided as a first connection terminal group 11 composed of staggered connection terminals 111 and 112. Is an alignment mark (not shown) on the heat sink 42 and a heating resistor on the resistance substrate 40
And is placed by mounting.

The drive substrate 411 on which the integrated circuit 2 is adhered is connected to the connection terminals 111, 112 of the resistance substrate 40.
And a second connection terminal group 21 composed of the staggered connection terminals 211 and 212 of the integrated circuit 2 on the drive substrate 41 at an appropriate distance, and a short distance and long distance connection terminals 111 connected to each other by a microscope or the like. The positions of 211, 112 and 212 are determined, and the adhesive is placed on the heat sink 42.

In this case, the height of the resistance substrate 40 and the integrated circuit 2
The height difference on the surface, that is, the step h, is preferably about 1 mm when considering the platen roller diameter of 40 mm and the auxiliary roller diameter of 10 mm shown in FIG.

At this time, the staggered first connection terminal group 11 on the resistance substrate 40 side and the staggered second connection terminal group 21 on the integrated circuit 2 side are located at long distances, ie, 111 and 211 and short distances. That is, the elements 112 and 212 are arranged opposite to each other, and are bonded by wires to complete the thermal printing head.

Here, the ratio of the step h between the bonding positions and the distance ISL of the short distance between the bonding positions and the distance OSL of the long distances, that is, the bonding step ratio is: bonding step ratio = h / ISL, h / OSL. Is represented. Also, if SL is included including ISL and OSL, h / S
L.

Next, the following table shows the bonding results obtained by changing the bonding step ratio from 0.35 to 0.80 according to the conventional method. However, the bonding was performed on the lower side first.

[0032]

[Table 1]

From the table, it can be seen that when the bonding step ratio between long distances is constant, the wire bending → wire contact → wire stepping phenomenon changes as the bonding step ratio between short distances increases.

Further, the probability of the peeling of the wire from the connection terminal 21 of the integrated circuit 2 to which the wire has been previously bonded increases when the bonding step ratio becomes 0.40 or less. Even if is small, the friction between the cavities is working and the distance between the bonding positions is large,
This is due to the longer wire.

In the judgment in the table, it is good that even if a wire contact occurs, the thermal printing head has thousands of wires between the steps, and the yield can be reduced if the wires are defective at several places. This is because the wire contact is extremely small and the contact portion can be repaired with a thin wire or the like, so that it is judged to be good.

In the same table, the stepping on the wire is defective as bonding because the wire is detached and repaired. It can be seen that the bonding step ratio at this time is 0.6 or more.

Accordingly, from the table, the bonding step ratio that can be repaired is 0.40 to 0.60, and the inner bonding step ratio when the connection terminals of short distance and long distance are opposed to each other in a staggered arrangement. Is 0.50 to 0.60, and the outer bonding step ratio is 0.40 to 0.45.

FIG. 4B shows a wiring state of wire bonding in the embodiment. In the table, those having a good judgment showed that there was no difference between the short-distance wire 471 and the long-distance wire 472 in the height direction on the bonding position side after bonding, and the bonding was performed at substantially the same level. This is because the wire is bonded to the next bonding position while pulling the wire while applying a frictional force to the wire in the capillary in the direction of the arrow in the drawing, that is, after bonding the wire to the first bonding position.

[0039]

According to the wire bonding method of the present invention, not only the contact between the connected wires is extremely reduced, but also if the contact occurs, the wire can be easily repaired. Further, the yield of the product is improved, and the number of repairs is reduced, so that the work efficiency of wire bonding is improved. Also, since the wire is less bent, the passage of the encapsulant for protecting the wire between the wires is improved, so that the contact of the wire in the encapsulation process can be prevented.

Further, by providing such a step, the distance between the auxiliary rollers can be reduced, the sagging and wrinkling of the thermal transfer film can be prevented, and fine transfer to plain paper can be performed.

[0041]

[Brief description of the drawings]

[0042]

FIG. 1 is an explanatory diagram of a thermal printing head,

[0043]

FIG. 2 is an explanatory cross-sectional view showing a state where recording is performed on plain paper via a thermal transfer film using a thermal printing head;

[0044]

3A and 3B are views showing step bonding by a conventional wire bonding method, wherein FIG. 3A is a plan view for explanation,
(B) is a sectional view for explanation,

[0045]

4A and 4B are diagrams showing step bonding according to an embodiment of the wire bonding method of the present invention, wherein FIG. 4A is a plan view for explanation, and FIG. 4B is a sectional view for explanation.

[0046]

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating resistor 2 ... Integrated circuit 3 ... Common electrode 4 ... Input signal group 11, 21 ... Connection terminal group 111, 112, 211, 212 ... Connection terminal 40 ... Resistor board 41 ... Drive Substrate 412: Common electrode substrate 42: Heat sink 43: Thermal transfer film 44: Plain paper 45: Platen rollers 461, 462: Auxiliary rollers 47, 471, 472, 471 ', 48, 49 Wire 51: ... capillary.

Claims (2)

(57) [Claims] 1. A first connecting terminal groups and a second wire bonding method that is adapted between the connecting terminal pairs are connected by bonding wires respectively corresponding phase connecting terminal groups arranged so as to face each other with a step At
The first connection terminal group and the second connection terminal group are close to each other.
The connection terminal pairs of the long distance and long distance
A step difference between the first connection terminal group and the second connection terminal group is h , and the first connection terminal group and the second connection terminal group are arranged in a bird shape.
Bonding position of connection terminal pairs in short distance between connection terminal groups
The distance between the terminals is ISL, and the bond
H / ISL, where OSL is the distance between
h / OSL is both 0.4 to 0.6 and h / IS
A wire bonding method characterized by having a relationship of L> h / OSL . 2. The wire bonding method according to claim 1, wherein the step h is in a range of 0.5 to 1.5 mm.