JPS60176245A - Wire bonding method - Google Patents

Abstract

PURPOSE:To reduce contact troubles between wires and to contrive to obtain highly compacted product, by a method wherein the specific relation is designed between the position difference of the first connecting terminal group and the second connecting terminal group, and the distance of bonding positions of corresponding terminal couples. CONSTITUTION:The first connecting terminal group 11 which is composed of zigzag type connecting terminals 111, 112 of a resistance base plate 40 and the second connecting terminal group 21 which are composed of zigzag type connecting terminals 211, 212 of a integrated circuit 2 on a drive base plate 41 keep an appropriate distance, and are placed and adhered on a heat sink 42. In this case, the ratio between the step differene (h) between bonding positions and the near distance OSL and the long distance ISL between the bonding position are made h/ISL=0.40-0.45 and h/OSL=0.50-0.60.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a wire bonding method, and particularly relates to a wire bonding method for wire bonding, and in particular, for bonding wire bonding between two Wire that reduces contact between wires when wiring between connecting terminals that are arranged in high density, and also makes it easy to repair contacts, making it possible to wire with high reliability between connecting terminals that have differences in level. The present invention relates to a bonding method.

[Technical background of the invention and its problems]

For example, a thermal printing head used in a facsimile machine will be explained with reference to FIGS. 1 and 2.

In other words, a plurality of heat generating resistors (
1), an integrated circuit for driving a heating resistor (hereinafter referred to as an integrated circuit) consisting of a shift register, a transistor drive, and a selector (2), and one end (10) of each heating resistor (1)
A common electrode (3) commonly connected to each heating resistor (1)
The main structure is an input signal group (4) for selectively energizing and generating heat via an integrated circuit (2), and each heating resistor (1)
The first group of connection terminals (11) from the integrated circuit (2) are provided so as to correspond to the second group of connection terminals (21) from the integrated circuit (2) which are selectively output, and the connection terminals are connected by wires. Connected by bonding.

Regarding the number of connection terminals in this second connection terminal group (21), it is generally said that 32 connection terminals per convergent circuit (2) is economically superior. Therefore, the heating resistor (1)
are connected to the second connection terminal group (21) from the integrated circuit (2) in units of 32. In the figure (5)
is an output signal terminal of the integrated circuit (2), and (6) is a power supply to the integrated circuit (2).

To record a facsimile using a thermal printing head with such a structure, a predetermined heating resistor (1) is selectively energized to generate heat, a thermal transfer film is brought into contact with the heating resistor (1), and the image is printed via the thermal transfer film. It is designed to be transferred onto plain paper.

To explain this state using FIG. 2, the heating resistor (1)
ceramic resistors and substrates (40) arranged with high density in a row perpendicular to the plane of the paper, a drive substrate (41+) on which a focusing circuit (2) is installed, and a common electrode on which a common electrode (3) is arranged. The substrate (412) is mounted and fixed on a heat sink (42) made of metal such as aluminum.

A thermal transfer film (43) coated with heat-softening ink and plain paper (44) are placed on the heating resistor (1) and slide into pressure contact with the heating resistor (1). It is inserted between the platen roller (45), and when the platen roller (45) rotates in the direction of the arrow (45t), both the thermal transfer film (43) and the plain paper (44) move in the direction of the arrow (5).
0) direction. In the figure (1
61) and (462) are auxiliary rollers that support the movement of the thermal transfer film (43).

・In addition, the thermal and printing head connections are made by connecting the first connection terminal group (11) from the heating resistor (1) and the second connection terminal group (21) from the output of the integrated circuit (2). Wire (47), one end (l) of the heating resistor (1)
a wire (48) connecting the integrated circuit (2) and the input signal group (4);
49), the circuit is constructed as shown in FIG.

With this structure, if the thermal transfer film (43) between the auxiliary rollers (461 and 462) becomes ``sag'' or 1' wrinkled, it will be transferred from the heating resistor (1) to the plain paper via the thermal transfer film (43). If the recording position on the auxiliary roller (461) shifts or the heat from the heating resistor (1) is not uniformly conducted, not only will the resolution of the recorded image deteriorate, but also delicate recording will not be possible. ) (462) is desirably as small as possible.

Therefore, as shown in the figure, a technique is proposed in JP-A-54-139 to provide a step between the resistor board (40), the drive board (411), and the common electrode board (412) to reduce the distance α.
It is shown in the No. 558 publication.

According to this publication, if the height difference is about 0.3 mm, it is possible to connect the height difference using the normal wire bonding method.
The effect of reducing the distance Q between 61) and 462 can hardly be expected. That is, 1. Usually, the thickness of the integrated circuit (2) is 0.
This is because it is 3 to 0.5 mm. From this, the height difference needs to be 0.5 to 1.5 mm.

Next, the main parts of FIGS. 1 and 2 will be explained with reference to FIG. 3.

That is, a first connection terminal group (11) in which connection terminals (111) and (112) are arranged in a staggered manner at the end of the lead wire from the heating resistor on the resistance board (40), and a drive board ( 4
1) Connect the output connection terminals (21r)' and (212) on the resistor board (1) side of the upper integrated circuit (2) with a second connection terminal group (21) arranged in a staggered manner. The comrades (111) and (21t) are arranged opposite to each other through the gap, and the comrades (111) and (21t) that are close to the step of the first connection terminal group (11) and the second connection terminal group (21), and the one that is far away Comrade (112) and (
212) and wire (47t) and
(472) to connect.

In this case, the resistor board (40) and the drive board (41) are on the same plane or have a step equal to the thickness of the integrated circuit (2), and wire bonding is performed from the higher side to the lower hem. As a method of connecting the first connection terminal group (11) and the second connection terminal group (21), the first connection terminal group (
11), close comrades of the second connection terminal group (21), that is, (
11+) and (212) and long-distance comrades, i.e. (112)
and (212), and close-range comrade wire (471).
JP-A-57-1 discloses a wire bonding method in which the height of the long-distance wire ('+72) is lower than that of the long-distance wire ('+72).
It is shown in Japanese Patent No. 65272.

However, this wire bonding method uses a gold wire with a diameter of 30 μm using a fully automatic bonder (Shingetsu Co., Ltd., model name SWB).
-FA-UTC-7) According to the experiment conducted by the proponents, the size of the step was the thickness of the integrated circuit (2), that is, in the range of 0.3 to 0.5 mm, and the wire length was 2 m.
Even if it is useful at a wire length of 0.5 mm or less, if the step is 0.5 mm or more and the wire length is 2 mm or more, the short-distance wire (47+) and the long-distance wire (47+), as shown in FIG.
472') from 20μm to 3
In extreme cases where the distance approached 0 μm, wires (471) and (472) came into contact as shown in FIG. 3(a).

Also, as shown in Fig. 3(a), wires (47□
) were found to have curves down to the bottom.

In particular, things that come into contact with each other are wires (471) and wires (471).
472) There is no comrade, but wire (47t) and wire (4
72) Occurs between. This is because fully automatic bonders use gold wire with a high elongation rate (7 to 10% at room temperature) to prevent wire breakage during bonding, so the wire is stretched at high speed and then shrinks, resulting in a wire loop. The only degree of freedom to maintain stability is in the direction perpendicular to the stretched wire, and it is thought that the wire may fall. Further, during the experiment, the wire collapse was unidirectional within one integrated circuit, and the contact position between the wires (47□) and (47□) was approximately at the center of the wires. Furthermore, as shown in FIG. 3(b), after bonding the wires (47+) that are close together, when attempting to bond the wires (472) that are long distance together, when the capillary (51) descends, this capillary (51) The tip and side ends of the wire (47,) come into contact with the wire (47,), and a phenomenon of wire stepping by the capillary (51) is observed, and the wire (47+) may be deformed as shown in (47,'). This is the wire tension that determines the wire loop shape when bonding where the step is 0.5 mm or more (usually a friction method is used to sandwich the wire).
To do this, loosen the wire ('+71). After bonding to the first connection point, the connection terminal (21, 1), wire ('+71) will become longer during bonding to the next connection point, the connection terminal (47□), so move it in the direction of the arrow. The wire (47) deforms outward from the connection terminal (211), which is the first connection point.
1) to the connection terminal (212), which is the first connection point, a phenomenon occurs in which the wire <41'1) is stepped on when the capillary (51) descends. This phenomenon is caused by the distance ISL between the bonding positions of the short-distance comrades' connection terminals 01.1) and (21□) and the long-distance comrades' connection terminal (
Distance DSL between bonding positions of H2) and (212)
It has been experimentally confirmed that this tendency is noticeable when the ratio of hlISL is inappropriate, especially when the hlISL ratio is large.

[Purpose of the invention]

This invention was made in view of the above-mentioned problems,
It is an object of the present invention to provide a wire bonding method between electrode groups having steps that can reduce contact accidents between wires and increase density.

[Summary of the invention]

That is, in the present invention, the pairs of corresponding connection terminals of the first connection terminal group and the second connection terminal group, which are provided to face each other with a step difference, are connected by wire honding. In the wire bonding method, a step between the first connection terminal group and the second connection terminal group;
Distance SL between bonding positions of corresponding connection terminal pairs
A wire bonding method characterized by having a relationship of h/5L=0.4 to 0.6 between
The connection terminal group and the second connection terminal group are respectively arranged in a staggered manner, and the short-distance and long-distance connection terminal pairs are made to correspond to each other, respectively, and the distance between the bonding positions of the short-distance connection terminal pairs is When ISL is ISL, and the distance between the bonding positions of the long-distance pair of connection terminals is O5L, h/I
SL = 0.40 to 0.45, hloSL = 0.
The relationship is between 50 and 0.60, and the difference in level is 0.
It is an embodiment that the wire bonding is in the range of 5 to 1.5 mm, and that the wire bonding is performed first on the side with the lower level difference and then on the side with the higher level difference.

[Embodiments of the invention]

In a thermal printing head, the number of heat-generating resistors is extremely large, approximately several thousand as described above, so the drive circuit is integrated to reduce the number of external peripheral circuits. In this case, the problem is how to efficiently and reliably connect the many thousands of heat-generating resistors to the output of the integrated circuit, the heat-generating resistors, and the common electrode, and how to prevent wires from falling during bonding. The point is how easily it can be repaired.

Regarding this point, the inventors further proposed that the first connection terminal group and the second connection terminal group, which are provided to face each other with a step in between, connect the corresponding connection terminal pairs by wire bonding. The results of various experiments and studies regarding wire bonding methods for connection.

As the step becomes larger, the wire becomes longer, so in order to prevent wire breakage, the wire tension must be lower than when the wire is short.To prevent the wire from sagging, the ratio between the step and the bonding position is optimized. It has been found that the slack in the wire can be eliminated by

In this case, if the size of the step is 0.5 mm or less, the conventional wire bonding method is possible, but if the step is 0.5 mm or more, the above-mentioned problem occurs, and if the step is 1.5 mm or less, the above-mentioned problem occurs. If the length exceeds 5 mm, the wire becomes long, and during bonding, a tensile force acts on the bonding position of the first wire and the connecting electrode, increasing the risk of peeling. This phenomenon (referred to as a phenomenon known as a phenomenon) occurs, and contact with adjacent wires increases, making it unsuitable for high-density wiring, such as one having nine connection terminals per 1 mm. Therefore, the range of the level difference in the wire bonding method of the present invention is from 0.5 mm to 1 mm.
, 5mm is optimal. Also, if you bond the wire to the side with a higher level difference first, when bonding the side with a lower level difference, especially if gold or aluminum wire is used, tensile force will be applied to the neck of the wire just above the bonding part, resulting in extreme In this case, there is a risk of peeling off at the bonding position, and also because of the constraint of reducing the distance between the auxiliary rollers of the product to which bonding is applied, it is preferable to bond the side with the lower level difference first.

Next, a fourth embodiment of the wire bonding method of the present invention will be described.
This will be explained using figures. However, the same reference numerals as in FIG. 3 indicate the same parts.

That is, the leading wires connected to a plurality of heating resistors (not shown) have staggered connecting terminals (]-11) at their tips.
, (112), which is arranged as a first connection terminal group (11), is connected to a heat sink (42).
) As shown above, alignment mat and resistor board (40)
It is aligned with the heating resistor above and placed by adhesive.

In addition, the drive board' (
41□) is the connection terminal (11□) of the resistance board (40), (
112) and the integrated circuit (2) on the drive board (41)
Keep an appropriate distance from the second connection terminal group (21) consisting of the staggered connection terminals (21+) and (212), and use a microscope etc. to inspect the connection terminals (111) for close and long distances.
, (21+), (112), and (212) are positioned and adhesively placed on the heat sink (42).

In this case, the difference between the height of the resistor board (40) and the height above the surface of the integrated circuit (2), that is, the level difference, is preferably around 1 mm, considering the platen roller diameter of 40 mm and the auxiliary roller diameter of 10 mm as shown in Fig. 2. , is 1 mm in this example.

At this time, the staggered first connection terminal group (11) on the resistance board (40) side and the staggered second connection terminal group (21) on the integrated circuit (2) side are long-distance comrades, that is, ( 11+) and (21
+) and close-range comrades (112) and (212) are placed facing each other, and a thermal printing head is completed by bonding them with wire.

Here, the ratio of the step difference between the bonding positions to the short distance O5L distance between the bonding positions and the long distance distance ISL, that is, the bonding step ratio is expressed as bonding step ratio=h/ISL=hloSl.

Furthermore, if SL includes ISL and O5L, it becomes h/SL.

Next, the following table shows the bonding results with the bonding step ratio varied from 0.25 to 0.80, including those obtained by the conventional method. However, bonding was performed on the lower side first.

(Left below) From the table, it can be seen that when the bonding step ratio between long-distance comrades is constant, as the bonding step ratio between short-distance comrades increases, the phenomenon changes from wire bending to wire contact to wire stepping.

Furthermore, the probability that the wire will peel off from the connection terminal (21) of the integrated circuit (2) to which the wire was bonded first increases when the bonding step ratio becomes 0.40 or less.
This is because when the step becomes larger, the wire becomes longer due to friction in the capillary acting even though the wire tension is small, and also because the distance between the bonding positions is large.

In addition, in the case of thermal printing heads, the number of wires between the steps is several thousand, and it is considered OK even if wire contact occurs in the judgment in the same table, and if wire contact occurs in a few places, the yield will decrease. Therefore, we judge that a product with very little wire contact and where the contact area can be repaired with a thin wire is good.

Also, in the same table, the wire stepping phenomenon is a defect in bonding because it requires repair without removing the wire. It can be seen that the bonding step ratio at this time is 0.6 or more.

Therefore, from the same table, the bonding step ratio that can be repaired is 0.4.
0 to 0.60, close range comrades in a staggered arrangement.

When long-distance connection terminals are placed opposite each other, the inner bonding step ratio is 0.40 to 0.45, and the outer bonding step ratio is 0.50 to 0.60.

FIG. 4(b) shows the wiring state of wire bonding in the embodiment. If the judgment is good in the table, on the bonding position side after bonding, the height direction is a wire of a short distance (47+), a wire of a long distance (47+), and a wire of a long distance (47+).
472) There was no difference between them, and they were bonded at almost the same level. This is because frictional force is applied to the wire within the capillary in the direction of the arrow in the figure, that is, after the wire is bonded to the first bonding position, it is bonded to the next bonding position while pulling the wire.

〔Effect of the invention〕

By using the wire bonding method of the present invention, not only is contact between connected wires extremely reduced, but even if contact occurs, it can be easily repaired. Furthermore, the product yield is improved and the number of repair parts is reduced, which improves wire bonding work efficiency. In addition, since the wires are less bent, the encapsulant that protects the wires can pass more easily between the wires, thereby preventing the wires from coming into contact during the encapping process.

Furthermore, by providing such a step difference, the distance between the auxiliary rollers can be reduced, preventing the thermal transfer film from sagging or wrinkling, allowing delicate transfer to plain paper.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the thermal printing head, Figure 2
The figure is an explanatory cross-sectional view showing the state of recording on plain paper via a thermal transfer film using a thermal printing head, and Figure 3 is a diagram showing step bonding by a conventional wire bonding method. is a plan view for explanation, FIG. 3(b) is a cross-sectional view for explanation, FIG. 4 is a diagram showing step bonding according to an embodiment of the wire bonding method of the present invention, and FIG. 4(a) is a diagram for explanation. FIG. 4(b) is a sectional view for explanation. 1...Heating resistor -...Integrated circuit 3...Common electrode 4...Input signal group 11, 21...Connecting terminal group 111, 112.21. , 212... connection terminal 40
...Resistance board 41...Drive board 412...
Common electrode substrate 42... Heat sink 43... Thermal transfer film 44... Plain paper 45... Platen roller 46. , 462... Auxiliary rollers 47, 471.
472, 47□', 48.49...Wire 51...
・Capillary agent Patent attorney Mr. Inoue Figure 1 Figure 3

Claims (4)

[Claims] (1) A wire bonding method in which pairs of corresponding connection terminals of a first connection terminal group and a second connection terminal group, which are provided to face each other with a difference in level, are connected by wire bonding, Said first
distance SL between the level difference between the connecting terminal group and the second connecting terminal group and the bonding position of the corresponding pair of connecting terminals;
A wire bonding method characterized by having a relationship of h/5L=0.4 to 0.6. (2) The first connection terminal group and the second connection terminal group are respectively arranged in a staggered manner, and the short-distance comrade connection terminal pairs and the long-distance comrade connection terminal pairs are respectively made to correspond to each other, and the short-distance comrade connection terminal pairs are The distance between the bonding positions is ISL, and the distance between the bonding positions of the pair of long-distance connection terminals is QS.
When L, h/ISL =0.40 to 0.45. h
10. The wire bonding method according to claim 1, wherein the wire bonding method has a relationship of 10SL=0.50 to 0.60. (3) The wire bonding method according to claim 1 or 2, wherein the step is in the range of 0.5 to 1.5 mm. (4) The wire bonding method according to any one of claims 1 to 3, wherein the wire is bonded to the side with the lower level difference first and the side with the higher level difference last.