JP3202851B2 - Lead and board bonding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining a lead and a substrate in a resin-sealed semiconductor device.

[0002]

2. Description of the Related Art Conventionally, bonding a lead to a semiconductor mounting substrate by heating and pressure bonding has been performed, for example, as disclosed in Japanese Patent Application Laid-Open No. 52-147067. That is, for example, a circuit 1 made of copper or the like
5A, the tip of the lead 2 used as an outer lead is overlapped on the circuit 13 as shown in FIG. 5A, and in this state, titanium or molybdenum is used as shown in FIG. 5B. The upper surface of the lead 2 is pressed and heated by the formed heating tool 14. Here, the surface of the circuit 13 is plated with nickel and gold, and the tip of the lead 2 is plated with tin. Then, as described above, when the tip of the lead 2 is overlapped with the circuit 13 and heated and pressed, the tin and gold plated on the surface of the lead 2 and the circuit 13 become Au-Sn eutectic alloy and melt. The lead 2 can be joined to the circuit 13 by using the -Sn eutectic alloy as a bonding layer.

[0003] The lead 2 can be joined to the circuit 13 by using tin and gold plated on the surface of the lead 2 or the circuit 13 as described above.
The bonding strength of the lead 2 to the semiconductor mounting substrate 1 is formed by the fillet 12 that the Sn eutectic alloy protrudes from the bonding surface of the lead 2 and the circuit 13 and adheres to the surface of the circuit 13 and the side surface of the lead 2. Can get higher.

[0004]

The fillet 12 is formed by the molten eutectic alloy being wet on the surface of the circuit 13 and the side surface of the lead 2, respectively. If the wettability of the eutectic alloy is good, FIG. The fillet 12 can be brought into close contact with the circuit 13 and the lead 2 as shown in FIG. However, if the heat transfer from the heating tool 14 to the joint is slow, Sn will be oxidized before the Au-Sn eutectic is formed, and the Au-Sn eutectic will not easily occur and the wettability will be poor. In such a case, the wettability is good as shown in FIG.
No fillet 12 is formed , and high joining strength cannot be obtained.

Conventionally, no attempt has been made to enhance the wettability of the eutectic alloy, and at present, high joining strength cannot be obtained. The present invention has been made in view of the above point, and has as its object to bond leads with high bonding strength.

[0006]

Method of bonding leads and substrate according to claim 1 of the present invention In order to achieve the above object, according to, when bonded by thermocompression bonding the tip portion of the lead 2 in the semiconductor mounting substrate 1, rie de <br / In order to increase the thermal conductivity in the joint surface direction of the lead 2 by forming the thickness of the tip portion of the lead 2 in the joint direction thin.
Ru der those.

A lead and a substrate according to claim 2 of the present invention.
Bonding method is that by recessing the groove 3 on the bonding surface of the lead 2, Ru der those to enhance the thermal conductivity of the bonding direction of the lead 2. Further , according to claim 3 of the present invention ,
The method of joining the lead and the substrate is as follows .
By recessing the, Ru der those to enhance the thermal conductivity of the bonding direction of the lead 2.

A lead and a base according to claim 4 of the present invention.
The method of joining the boards is to increase the width of the lead 2 near the edge of the semiconductor mounting substrate 1 to form the wide portion 6 ,
Forming the narrow portion 5 by narrowing the width of the tip of the
Therefore, the thermal conductivity is increased in the bonding surface direction of the lead 2.
It was made . Further, according to the present invention, the plurality of leads 2 on which the wide portions 6 are formed as described above are connected to the semiconductor mounting substrate 1.
When joining the adjacent leads 2 to the wide portions 6
It is preferable to dispose the leads 2 so that the leads 2 are shifted in the longitudinal direction of the leads 2.

[0009]

[0010]

[0011]

When the tip of the lead 2 is bonded to the semiconductor mounting substrate 1 by heating and pressing, the heat from the heating tool 14 is transferred by increasing the thermal conductivity in the direction of the bonding surface of the lead 2 and performing heating. It can be quickly transmitted to the joint surface through the lead 2 having improved wettability, and can form a eutectic before the brazing material metal is oxidized to form a fillet of a eutectic metal having good wettability.

[0012]

The present invention will be described below in detail with reference to examples. The semiconductor mounting substrate 1 is made of a laminated plate of a modified polyimide resin or the like. The semiconductor chip mounting portion is formed at the center portion, and the periphery of the surface of the semiconductor mounting substrate 1 is surrounded by the semiconductor chip mounting portion. A large number of circuits 13 are formed at the ends by copper foil or the like as shown in FIGS. The surface of the circuit 13 is plated with nickel and the surface thereof is further plated with gold.

On the other hand, the lead 2 is formed of a 42 alloy or the like as an outer lead by, for example, a lead frame or the like, and at least a joining surface at a tip portion thereof is plated with tin. Then, the lead 2 is connected to the semiconductor mounting substrate 1
When bonding by heating and pressing to the circuit 13 of FIG.
As shown in FIG. 3B, the upper surface of the lead 2 is heated by a heating tool 14 made of titanium, molybdenum or the like. For example, the heating temperature (the temperature of the contact portion of the tool 14) is set to 350 ° C., the energizing time (temperature holding time) to the tool 14 is set to 2 seconds, and the pressurization per lead 2 is set to 150 gf. Can be. Then, when the tip of the lead 2 is overlapped with the circuit 13 and heated and pressed as described above,
As described above, tin and gold plated on the surfaces of the leads 2 and the circuit 13 are melted as an Au-Sn eutectic alloy, and the Au-Sn eutectic alloy is used as a bonding layer to form the circuit 13.
The lead 2 can be joined to the first. As described above, tin and gold plated on the surfaces of the leads 2 and the circuit 13 are joined as a brazing material, but the brazing material is not limited to tin or gold.

By bonding the lead 2 to the semiconductor mounting substrate 1 in this manner, the semiconductor chip 15 mounted on the semiconductor mounting substrate 1 as shown in FIG. The connected semiconductor device A can be manufactured, and further, it can be finished into a product by sealing it with a resin. FIG. 1 shows an embodiment of the present invention. A thin portion 17 is formed at the tip of the lead 2 by removing the surface (upper surface) of the lead 2 opposite to the bonding surface by half etching or the like. I have to do it. The means for forming the thin portion 17 is not limited to half-etching, but is arbitrary, and its size and shape are not particularly limited. And FIG. 1 (a)
The tip of the lead 2 is connected to the circuit 1 of the semiconductor mounting substrate 1 as shown in FIG.
3 and hot-pressed with a heating tool 14 so that tin and gold plated on the lead 2 and the circuit 13 are Au-S
The lead 2 can be joined to the circuit 13 as shown in FIG. 1B by the Au-Sn eutectic alloy, which is melted.

In the thermocompression bonding as described above, the tip of the lead 2 is thinned in the joining direction by the thin portion 17, so that the distance from the tip of the heating tool 14 to the joining surface is shortened. Thermal conductivity is increased, and heat conduction from the heating tool 14 to the bonding interface is increased. In addition, by reducing the thickness, the heat capacity of the tip of the lead 2 is reduced, and the temperature rises faster. As described above, even when the lead 2 is formed of a material having a low thermal conductivity such as a 42 alloy, the conduction of heat from the heating tool 14 and the temperature rise are also fast due to the thin portion 17, so that the tin 2 Au-Sn eutectic can be formed quickly before is oxidized, and the wettability of the Au-Sn eutectic alloy can be improved. Therefore, the fillet 12 shown in FIG. 6A having good wettability to the surface of the circuit 13 and the side surface of the lead 2 is provided.
The fillet 12 is brought into close contact with the circuit 13 and the lead 2 so that the lead 2
High joining strength can be obtained.

When the thin portion 17 is formed on the lead 2 and joined to the semiconductor mounting substrate 1, the joining is performed in a state where the base of the thin portion 17 extends outside the edge of the semiconductor mounting substrate 1 as shown in FIG. Then, the thickness of the edge portion (indicated by the arrow) where the bending stress concentrates on the lead 2 becomes thinner, and this portion may be easily bent and may be broken. For this purpose, as shown in FIG.
It is preferable to join the leads 2 such that the base of the lead 2 is located inside the edge of the semiconductor mounting substrate 1.

FIG. 7 shows an embodiment in which the groove 3 is recessed in the joint surface of the lead 2. In the embodiment of FIG. A plurality of grooves 3 are provided in parallel. Then, the tip of the lead 2 is placed on the circuit 13 of the semiconductor mounting substrate 1 so that the heating tool 1
4, the lead 2 and the circuit 13
The tin and gold plated in the form of an Au-Sn eutectic alloy melt and the lead 2 can be joined to the circuit 13 by the Au-Sn eutectic alloy. In performing the thermocompression bonding as described above, the heat capacity of the leading end of the lead 2 is reduced due to the formation of the groove 3, and the heat from the heating tool 14 is quickly transmitted to increase the temperature quickly. Therefore, an Au-Sn eutectic can be quickly formed before tin is oxidized, and the wettability of the Au-Sn eutectic alloy can be improved, and the wettability to the surface of the circuit 13 and the side surface of the lead 2 can be improved. By forming a good fillet 12 as shown in FIG. 6A, the bonding strength of the lead 2 to the semiconductor mounting substrate 1 can be increased. By forming the groove 3 in the joint surface of the lead 2, the fillet 12 is also formed in the groove 3, and the joint area by the fillet 12 increases, so that the joint strength can be further improved. It is.

In the embodiment shown in FIG. 7B, a groove 3 is formed in the vicinity of the bonding surface of the tip of the lead 2 facing the edge of the semiconductor mounting substrate 1. Even in this case, the heat capacity of the leading end of the lead 2 becomes small due to the formation of the groove 3, the heat from the heating tool 14 is quickly transmitted, the temperature rises quickly, and the Au is quickly oxidized before tin is oxidized. -Sn eutectic can be formed to improve the wettability of the Au-Sn eutectic alloy, and the fillet 12 as shown in FIG. Is formed so that the bonding strength of the lead 2 to the semiconductor mounting substrate 1 can be increased. Further, as shown in FIG. 7B, a large fillet 12 is formed in the groove 3 at the edge of the semiconductor mounting substrate 1,
The peel strength of the lead 2 bonded to the semiconductor mounting substrate 1 can be increased.

In the embodiment shown in FIG. 7 (c), an inverted V-shaped groove 3 is formed in the vicinity of the bonding surface at the tip of the lead 2 facing the edge of the semiconductor mounting substrate 1. In this case, a fillet 12 can be stably formed in the groove 3 by irradiating the groove 3 with a laser beam and heating it using a laser device. Since the groove 3 has an inverted V-shape, the laser light is multiple-reflected as shown by the arrow, and the fillet 12 can be formed by efficiently raising the temperature. As described above, since the fillet 12 having a large area is formed in the groove 3 at the edge of the semiconductor mounting substrate 1, the peel strength of the lead 2 joined to the semiconductor mounting substrate 1 can be increased.

FIG. 8 shows an example in which a recessed step 4 is formed on the joint surface of the lead 2. The lower surface of the recessed step 4 is formed on the semiconductor mounting substrate 1 as shown in FIG. The lead 2 and the tin and gold of the circuit 13 are brought into contact with the surface of the circuit 13 by bringing the step surface 4a of the concave step portion 4 into contact with the side end surface of the semiconductor mounting substrate 1 and by applying heat and pressure with the heating tool 14. Au
The lead 2 can be joined to the circuit 13 by the Au-Sn eutectic alloy and melting. In this thermocompression bonding, the tip of the lead 2 has a reduced thickness in the joining direction due to the concave step portion 4, so that the thermal conductivity is increased, and heat conduction from the heating tool 14 to the joining interface is faster. In addition, since the thickness is thin, the heat capacity of the tip of the lead 2 is small, and the temperature rise is fast. Therefore, Au is quickly oxidized before tin is oxidized.
-Sn eutectic can be formed, and the fillet 12 as shown in FIG. 6A having good wettability to the surface of the circuit 13 and the side surface of the lead 2 by improving the wettability of the Au-Sn eutectic alloy can be obtained. It is possible to obtain a high bonding strength of the lead 2 to the semiconductor mounting substrate 1 by forming it.

In the embodiment shown in FIG.
A concave step 18 is also provided at the edge of the lead 2, and the base of the concave step 4 of the lead 2 is fitted into the concave step 18, and the lead 2 is bonded to the semiconductor mounting substrate 1 by heating and pressing. is there. In the embodiment shown in FIG. 8A, when a force as shown by an arrow is applied to the lead 2 at the edge of the semiconductor mounting substrate 1, a shear force acts on a thin portion at the base of the concave step portion 4. Although it is weak against the shearing force, FIG.
In the case of (b), the shearing force acts on the thick part of the lead 2 and the lead 2 becomes strong against the shearing force.

In the embodiment shown in FIG. 9, the width of the tip of the lead 2 is reduced to form the narrow portion 5. Lead 2
The means for reducing the width of the tip of the is arbitrary, and its size and shape are not particularly limited. Then, the tip of the lead 2 is superimposed on the circuit 13 of the semiconductor mounting substrate 1 and heated and pressed by the heating tool 14, so that tin and gold plated on the lead 2 and the circuit 13 are melted as an Au-Sn eutectic alloy. This Au—Sn eutectic alloy makes the circuit 13
Can be joined to the lead 2. In this thermocompression bonding, the heat capacity is reduced by making the distal end of the lead 2 a narrow portion 5 so that the heating tool 14
Heat is quickly transmitted and the temperature rises faster. Therefore, an Au-Sn eutectic can be quickly formed before tin is oxidized, and the wettability of the Au-Sn eutectic alloy can be improved, and the wettability to the surface of the circuit 13 and the side surface of the lead 2 can be improved. By forming a good fillet 12 as shown in FIG. 6A, the bonding strength of the lead 2 to the semiconductor mounting substrate 1 can be increased.

[0023] In forming a narrow portion 5 by narrowing the width of the tip portion of the lead 2, as described above, the semi-conductor mounting board 1
A wide portion 6 wider than the width of the lead 2 is provided in the vicinity of the edge portion. The means for providing the wide portion 6 is optional, and its size and shape are not particularly limited. Then , the leading end of the lead 2 is overlapped on the surface of the circuit 13 so that the wide portion 6 is brought into contact with the surface of the circuit 13 at the edge of the semiconductor mounting substrate 1.
The lead 2 is joined by heat-compression bonding . But in which it is possible to obtain high bonding strength of the lead 2 as described above by the front end portion of rie de 2 a narrow part 5, the base portion of the narrow portion 5 becomes wide portion 6 circuit 13, the bonding area of the lead 2 is large at the edge of the semiconductor mounting substrate 1, and the peel strength of the lead 2 bonded to the semiconductor mounting substrate 1 can be improved.

[0024] When the plurality of bonding leads 2 formed by providing a wide portion 6 as described above in the semiconductor mounting substrate 1, FIG. 1
0 (b), the wide portions 6 of the adjacent leads 2 are close to each other, and there is a possibility that a short circuit occurs between the leads 2. Therefore as shown in FIG. 10 (a) in this case, adjacent the wide portion 6 leads 2 be arranged in a zigzag pattern so as to shift in the longitudinal direction of the lead 2, the wide portions of the adjacent leads 2 6 are prevented from approaching each other to prevent a short circuit from occurring between the leads 2.

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

As described above, according to the first aspect of the present invention , the thickness of the tip of the lead in the direction of the joining surface is reduced when the tip of the lead is bonded to the semiconductor mounting substrate by heating and pressing.
By increasing the heat conductivity in the direction of the joint surface of the lead, the heat from the heating tool can be quickly transmitted to the joint surface through the lead with increased thermal conductivity, and An eutectic can be formed before the metal is oxidized to form a fillet with a eutectic metal having good wettability, and the lead can be joined with high joining strength.

According to a second aspect of the present invention , a groove is formed in the joint surface of the lead, so that heat is transferred in the direction of the joint surface of the lead.
Heating with increased conductivity, so from the heating tool
Heat is quickly transferred to the joint surface through the leads with enhanced thermal conductivity
Eutectic before the brazing metal is oxidized.
To form a fillet of eutectic metal with good wettability
The lead can be connected with high bonding strength.
Can be combined .

Further , according to a third aspect of the present invention, a concave step is provided on the joint surface of the lead, so that the direction of the joint surface of the lead is reduced.
The heat conductivity is increased by heating the
The heat from the
Can be conveyed to the joint surface, before the brazing metal is oxidized
Create eutectic and fillet with eutectic metal with good wettability
It can be formed and has high bonding strength.
Can be joined .

According to a fourth aspect of the present invention, a semiconductor
Increase the lead width near the edge of the mounting board to make it wider
And narrow the tip of the lead to make it narrower.
The lead is formed by the narrow part.
Can increase the thermal conductivity in the joining direction,
Fillets can be formed from eutectic metals with good wettability.
At the same time , the bonding area of the lead can be increased in the wide portion, and the peel strength of the lead bonded to the semiconductor mounting substrate can be improved. Further, in the present invention, when joining the plurality of leads having the wide portions formed as described above to the semiconductor mounting substrate, adjacent leads are arranged such that the wide portions are shifted in the longitudinal direction of the leads. Therefore, the wide portions of the adjacent leads can be prevented from approaching each other, and a short circuit between the leads can be prevented.

[0035]

[0036]

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, in which (a),
(B) is a side view, respectively.

FIG. 2 is a side view of another embodiment of the embodiment.

FIG. 3 shows a semiconductor mounting substrate and leads,
(A) is a side view, (b) is a partial plan view.

FIG. 4 is a side view of the semiconductor device.

FIGS. 5A and 5B show a step of connecting leads by a heating tool, and FIGS. 5A and 5B are side views.

FIGS. 6A and 6B show the state of the fillet at the joint of the lead, and FIGS. 6A and 6B are enlarged cross-sectional views.

FIG. 7 shows another embodiment of the present invention, in which (a)
(C) is a partial side view.

FIG. 8 shows still another embodiment of the present invention;
(A) and (b) are each a partial side view.

FIG. 9 is a partial plan view of still another embodiment of the present invention.

FIGS. 10A and 10B show still another embodiment of the present invention, and FIGS . 10A and 10B are partial plan views, respectively .

[Explanation of symbols]

1 semiconductor mounting substrate 2 leads 3 groove 4 recessed step 5 narrow portion 6 wide part 7 slit 8 tapered notch

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-181157 (JP, A) JP-A-48-51258 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 23/50 H01L 23/12

Claims (5)

(57) [Claims] When joining a lead end portion of a lead to a semiconductor mounting substrate by heating and pressing, the thickness of the lead end portion in the joining direction is reduced to enhance thermal conductivity in a joining surface direction of the lead. And heating the lead and the substrate. 2. A method of heating and bonding a lead end portion of a lead to a semiconductor mounting substrate by heating and compressing the lead end portion by forming a groove in the lead joining surface so as to increase thermal conductivity in a direction of the lead joining surface. A method for joining a lead and a substrate, characterized in that: 3. When joining the lead end portion of the lead to the semiconductor mounting substrate by heating and press bonding, a concave step is provided on the joining surface of the lead, thereby increasing the thermal conductivity in the direction of the joining surface of the lead and heating. A method for joining a lead and a substrate. 4. A method for bonding a lead end portion of a lead to a semiconductor mounting substrate by heating and pressure bonding to form a wide portion by increasing a lead width in the vicinity of an edge portion of the semiconductor mounting substrate and to form a wide end portion of the lead. A method for bonding a lead and a substrate, comprising: increasing the thermal conductivity in the direction of the bonding surface of the lead by forming a narrow portion by reducing the thickness of the lead. 5. A method of joining a plurality of leads having a wide portion according to claim 4 to a semiconductor mounting board, wherein adjacent leads are arranged such that the wide portions are shifted in the longitudinal direction of the leads. Method of joining the lead and the substrate.