JP2002093984A - Lead frame brazing method in electronic component package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of jigs required at the time of brazing a lead frame in an electronic component package and to improve cost performance, efficiency, operability and working accuracy. SOLUTION: A brazing filler metal 12 in a plate piece shape composed of silver solder for instance is set to the lead frame 10 set on a work bench 14, and the brazing filler metal 12 is temporarily brazed to the lead frame 10 by using a YAG laser beam LB emitted from a laser emission unit 16. At the time of the temporary brazing, the vicinity of the boundary of the brazing filler metal 12 and the part 10a to be brazed of the lead frame 10 is irradiated with the YAG laser beam LB. Preferably, the beam spot center of the YAG laser beam LB is matched with the boundary. After the temporary brazing, the lead frame 10 and the brazing filler metal 12 are set to a package main body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technique for brazing a lead frame to a package conductor of an electronic component package.

[0002]

2. Description of the Related Art Conventionally, in a ceramic package, in order to electrically connect an electrode of a built-in semiconductor chip to an external lead, a ceramic base is subjected to a metallizing process so as to be exposed on a side surface or a back surface of the package. A package conductor is formed, and a lead frame is joined to the package conductor by brazing.

FIGS. 8 and 9 show a conventional example of a lead frame brazing method for a ceramic package. In this method, in order to braze the lead frame 102 to the package conductor of the ceramic package body 100,
Three fixing jigs, base 1 for fixing package body
04, a spacer 106 for fixing the brazing material and a weight 108 for fixing the lead frame are used.

[0004] Specifically, the ceramic package body 100 is accommodated and fixed in a recess 104a formed in the center of the upper surface of the base 104 with the ceramic package body 100 turned upside down, that is, with the package back surface where the package conductor is exposed facing upward. The lead frame 102 is overlaid on the package conductor surface via a brazing material, for example, a silver brazing 110. Here, each conductor (not shown) arranged in each row of the package conductor surface
Are positioned so that the respective tips or the brazed portions 102a of the lead frame 102 overlap with the top. For this alignment, guide pins 112 are erected at a plurality of predetermined positions on the upper surface of the base 104, and guide holes 102b that can be fitted with the respective guide pins 112 are provided at corresponding positions on the lead frame 102 side. Are formed.

However, the package body 10
Even when the lead frame 102 and the lead frame 102 are aligned with each other, there is a possibility that the brazing material 110 sandwiched between them may cause a positional shift. Therefore, a plate-like spacer 106 is arranged on the package body to regulate the position of the brazing material 110 on the package conductor row from inside. Furthermore, when vibration or shock is applied when the brazing material 110 is melted in a heating furnace, the brazing material may be cracked or displaced, so that the brazing material is weighted so as to cover the lead frame 102 in the base recess 104. Put 108.

[0006]

In the conventional lead frame brazing method as described above, several jigs (104, 106, 10) are required for one type of ceramic package.
8), a large number of jigs must be prepared in accordance with various package shapes and package conductor patterns appearing on the market now and in the near future, resulting in high mounting costs. Also, in the field workers,
If the type and number of jigs are large, management and handling are troublesome, and it is easy to make mistakes.For example, the user may forget to install the required jigs. When melted, the positions of the lead frame and the brazing material are shifted due to vibration or the like, which may result in poor bonding.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and reduces the number of jigs required for brazing a lead frame in an electronic component package, thereby reducing cost and efficiency. And a method for improving workability.

Another object of the present invention is to provide a method for improving the processing accuracy when brazing a lead frame in an electronic component package.

Another object of the present invention is to provide a method for safely and successfully brazing a lead frame in an electronic component package.

In order to achieve the above-mentioned object, a first method of the present invention is a method of brazing a lead frame to a package conductor exposed on a main body of an electronic component package. A step of locally melting and temporarily attaching a predetermined brazing material to the brazed portion of the lead frame with the energy of laser light; and positioning the lead frame temporarily attached to the package conductor with the brazing material interposed therebetween. The method includes a step of combining and overlapping, and a step of melting all or most of the brazing material by heating and joining the package conductor and the lead frame.

In the first method of the present invention, the lead frame 10 and the brazing material 12 which are preliminarily attached and integrated are set in the ceramic package body 20 in advance. Even if vibration or impact is applied after the setting, the brazing material is temporarily fixed to the lead frame, so that there is no risk of displacement. Therefore, the brazing material melts at the predetermined position. The melted brazing material moves so as to be attracted from the surface of the package body having low wettability to the package conductor having high wettability, and solidifies there. As a result, the corresponding brazed portions of the lead frame are brazed so as to overlap the respective package conductors of the ceramic package body.

[0011] Preferably, the temporary attaching step in the first method includes a step of superposing the brazing material on a brazed portion of the lead frame, and a step of placing the laser light near a boundary between the brazing material and the lead frame. Irradiation step. Thus, by irradiating the laser beam near the boundary between the brazing material and the brazed portion of the lead frame, preferably by irradiating the laser beam with the laser beam center portion aligned with the boundary, the localization of the brazing material is performed. Laser energy can be safely and efficiently applied to the workpiece, and good tacking can be performed.

A second method of the present invention is a method of brazing a lead frame to a package conductor exposed to be provided on a main body of an electronic component package, wherein a predetermined brazing material is sandwiched between the package conductors. A step of aligning and superposing the frames, a step of locally melting the brazing material with the energy of the laser beam, and temporarily attaching the lead frame to the package conductor, and heating the brazing material in whole or in total. Joining the exposed conductor and the lead frame by partially melting.

In the second method, the lead frame, the brazing material, and the package body (strictly, the package conductor) are set, and then a part of the brazing material is locally melted by the energy of the laser beam. And the three are tacked together. Thereafter, even if vibrations or shocks are applied, the brazing material is temporarily fixed to the lead frame and the package body, so that there is no risk of displacement. Therefore, similarly to the first method, there is no displacement of the brazing material, and the positional accuracy of the lead frame brazing is high.

In this method, preferably, the temporary attaching step may include a step of irradiating a laser beam to one side surface or a peripheral surface of the brazing material through a gap between the electronic component package body and the lead frame. With this laser irradiation method, laser energy can be efficiently supplied to the brazing material, and laser irradiation marks on the lead frame can be hidden in the gap.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS.

FIGS. 1 and 2 show a method of temporarily attaching a brazing material 12 to a lead frame 10 in one embodiment of the present invention.

First, as shown, the lead frame 10 is set on the worktable 14. Here, the lead frame 10 is arranged in such a posture that the brazed portion 10a at the tip thereof faces upward. A plurality of guide pins 14a, for example, a pair of guide pins 14a are erected at predetermined positions on the work table 14, and each guide hole 10b on the lead frame 10 side is fitted into each corresponding guide pin 14a, so that the work table 14 The positioning and fixing of the lead frame 10 are performed.

A plate-shaped brazing material 12 made of, for example, silver brazing is set on the lead frame 10 set on the work table 14 as described above. Specifically, the brazing material 1 is placed on the brazed portion 10a so as to traverse the entire brazed portion 10a of the lead frame 10 from end to end.
Stack two. At this time, as shown in FIG. 2, the brazed portion 10a of the lead frame 10 is
The width W of the brazing material 12 is set so as to protrude from the brazing portion 1.
If the size is selected to be shorter than the length L of Oa, the work can be performed more easily.

Next, the brazing material 12 is temporarily attached (temporarily joined) to the lead frame 10 using the YAG laser light LB emitted from the emission unit 16 of the laser device, for example, the YAG laser device. Preferably, the temporary attachment points P may be set at a plurality of locations. For example, as shown, a temporary attachment point P may be set at the brazed portions 10a at both ends of the lead frame 10.

At the time of this temporary attachment, the YAG laser light L
How to apply B (irradiation method) is important. That is, FIG.
As shown in FIG. 1, the boundary E1 between the brazing material 12 and the brazed portion 10a of the lead frame 10 protruding from underneath.
It is important to irradiate the YAG laser beam LB from above to around 2,10, and preferably to align the center of the beam spot of the YAG laser beam LB with the boundary E12,10.

When the YAG laser beam LB is applied only to the brazing material 12 side, since the light reflectance of the brazing material (silver) 12 is high, most of the incident laser light LB is reflected there and the laser energy is reduced. Is not absorbed well and brazing material 1
2 does not melt easily. Further, when the YAG laser beam LB is irradiated only on the lead frame 10 side, the energy of the incident laser beam LB hardly moves to the brazing material 12, so that the brazing material 12 is hardly melted. When the output of the laser beam LB is increased to compensate for such low energy absorption or transmission efficiency, the laser energy is applied to the lead frame surface (front surface after mounting) opposite to the brazed portion 10a. May be penetrated and laser irradiation marks may be formed, which is not preferable.

In this regard, as in this embodiment, the brazing material 1
In the method of irradiating the laser beam LB to the boundary E12, 10 between the soldering portion 10a of the lead frame 10 and the portion 2 protruding from below, the energy of the incident laser light LB is changed from the gap between the boundary E12, Furthermore, lead frame 1
By efficiently reaching the brazing material 12 from the 0 side,
The vicinity of the laser-irradiated portion of the brazing material 12 can be reliably melted with a small laser energy and can be temporarily attached to the lead frame 10 by brazing. The YAG laser beam LB may be a pulse laser beam, for example, having a pulse width of about 5 ms and a laser energy per pulse of 1.
It may be set to about 5J.

The YAG laser beam LB having such a small laser energy is applied to the lead frame 10.
Is irradiated to the brazed portion 10a side.
There is no laser irradiation mark (scratch) on the front surface of the lead frame on the side opposite to a. This quality advantage is practically significant. This is because, in an electronic component package usually obtained by brazing a lead frame, a lead surface having a visible scratch has no commercial value in the market. Incidentally, the lead frame 10 is formed by spot welding.
The method of temporarily attaching the brazing material 12 to the lead frame 10 is as follows.
There is a disadvantage that traces of the electrodes are inevitably attached to the front surface.

After the brazing material 12 is temporarily attached to the lead frame 10 as described above, the lead frame 10 is brazed to the electronic component package body. In this embodiment, as shown in FIGS. 3 and 4, only a package fixing base 18 is used as a brazing fixing jig. The material of the base 18 may be excellent in heat resistance and hardly wet by the brazing material, for example, carbon.

3 and 4, in a recess 18a formed in the center of the upper surface of the base 18, the ceramic package body 20 is turned upside down, that is, the package back surface where the package conductor 20a is exposed faces upward. It is stored and fixed. The lead frame 10 is overlaid on the ceramic package body 20 housed and fixed in the recess 18a with the brazing material 12 interposed therebetween.

In the ceramic package body 20 of this embodiment, a plurality of (five in the illustrated example) package conductors 20a are exposed and metallized at both left and right end portions on the back surface of the package. Each package conductor 20a
Inside the main body 20, it is electrically connected to each corresponding electrode of the built-in semiconductor chip by wire bonding. The lead frame 10 is a single package conductor 20a for one row.
It corresponds to. Accordingly, for the ceramic package body 20 of this example, a pair of lead frames 10 are respectively applied to the left and right rows of package conductors 20a as shown in the figure. At this time, positioning is performed so that each brazed portion 10a of the lead frame 10 overlaps each package conductor 20a. For this alignment, for example,
The lead frame 1 is provided on the upper surface of the base 18 at a plurality of predetermined positions.
A guide pin 22 that can be fitted into the zero guide hole 10b may be provided upright.

In this embodiment, as shown in FIGS. 3 and 4, the lead frame 10 is positioned and stacked on the base 18 with the brazing material 12 interposed between the package conductors 20a of the ceramic package body 20. , And passed through a heating furnace (shown), and heated in the furnace for a predetermined time to melt the brazing material 12. At this time, even if vibration or impact is applied during transportation for some reason, the brazing material 12 is temporarily attached to the lead frame 10 and fixed in advance, so there is no possibility of displacement, and the brazing material 12 melts at a predetermined position. When the brazing material (silver brazing) 12 is melted, the ceramic package body 20 is melted.
On the backside of the package, the solder 12 has a low wettability from a ceramic surface to an adjacent package conductor 20 having a high wettability.
Move so as to be attracted to a. Then, when leaving the heating furnace, the solder 12 is solidified on each package conductor 20a, and the lead frame 10 is soldered. In this embodiment, brazing is performed through a heating furnace, but brazing may be performed by irradiating a laser beam or a light beam.

FIG. 5 shows the lead frame 10 in the ceramic package body 20 taken out from the base 18.
3 shows the joined state. As shown, each corresponding brazed portion 10a of the lead frame is brazed on each package conductor 20a of the ceramic package body 20 so as to overlap.

As described above, in this embodiment, the lead frame 10 in the ceramic package body 20 is used.
The only fixing jig necessary for brazing is a base 18 for fixing the ceramic package body 20.
2 and a jig (10
6,108) is not required. Therefore, the cost of the jig and the cumbersome work and management are eliminated. Moreover,
In order to temporarily attach the brazing material 12 to the lead frame 10 and then set it on the ceramic package body 20, the brazing material 1
2. There is no positional deviation, and the positional accuracy or working accuracy of the brazing can be improved. Further, by using the laser energy of the laser beam LB for the temporary attachment, the risk of the lead frame 10 being damaged can be avoided.

Next, another embodiment of the present invention will be described with reference to FIGS. In this embodiment, a lead frame 10, a brazing material 12, and a ceramic package body 2 are used.
0 are temporarily attached simultaneously by the energy of the laser beam LB.

More specifically, as shown in FIG. 6, these three members (10, 1) are placed on a suitable work table or jig (not shown).
2, 20) are aligned with each other and overlapped integrally. At this time, the package conductors 20 provided in a row at the left and right ends of the back surface of the ceramic package body 20 are provided.
a, the brazed portion 10a of the lead frame 10 overlaps with the brazing material 12 interposed therebetween. As shown in FIG.
Preferably, the outer side surface 12a of the brazing material 12 is located in the gap G between the ceramic package body 20 and the lead frame 10.

Then, as shown in FIG. 7, a YAG laser beam LB is applied to the vicinity of the side surface 12a of the brazing material 12 through the gap G from the emission unit 16 in the horizontal position. YAG
Since the laser beam LB enters not only the brazing material 12 but also the lead frame 10 and the ceramic package body 20 in the gap G, laser energy is efficiently supplied to the brazing material 12, and the brazing material 12 is locally melted. As described above, the lead frame 10 is temporarily attached to the ceramic package body 20 at a location where the brazing material 12 is locally melted. A plurality of such temporary attachment points Q may be set in the entire ceramic package. For example, as shown in FIG. 6, the temporary attachment points Q are set at the brazed portions 10a at both ends of each lead frame 10. Good.

Next, the assembly of the lead frame 10, the brazing material 12, and the ceramic package body 20 integrated by the above-described temporary attachment is passed through a heating furnace,
All or most of the brazing material 12 is melted in the furnace. Thereby, the same brazing result as in FIG. 5 is obtained. In other words, the corresponding brazed portions 10a of the lead frame are overlaid on the respective package conductors 20a of the ceramic package body 20 and brazed.

Also in this embodiment, the number of jigs required for brazing the lead frame 10 in the ceramic package body 20 can be greatly reduced, and the positional accuracy of brazing can be improved. Also, when tacking,
Since the laser beam LB is irradiated into the gap G between the ceramic package body 20 and the lead frame 10, even if a laser irradiation mark is formed on the surface of the lead frame 10 in the gap G, it is hardly visible from the outside. Has no effect.

The structure and shape of each part in the above-described embodiment are merely examples, and do not limit the technical idea of the present invention. For example, the ceramic package 20 in the above embodiment is a dual in-line (DIP)
Type, but any other package structure such as S
The present invention is also applicable to IP and PGA types. The shape of the brazing material in the present invention is not limited to a plate-like shape as in the above embodiment, but may be, for example, a columnar shape. Further, a CO2 laser, a semiconductor laser, or the like can be used instead of the YAG laser.

[0036]

As described above, according to the present invention,
In addition to reducing the number of jigs required for brazing lead frames in electronic component packages, cost, efficiency and workability can be improved, and the processing accuracy, safety and quality of brazing can also be improved. .

[Brief description of the drawings]

FIG. 1 is a view showing a method of temporarily attaching a brazing material to a lead frame in one embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration and an operation of a main part in temporary attachment according to the embodiment.

FIG. 3 is a cross-sectional view illustrating a configuration of a main part in brazing according to the embodiment.

FIG. 4 is a plan view showing a configuration of a main part in brazing according to the embodiment.

FIG. 5 is a plan view showing a result of brazing in the embodiment.

FIG. 6 is a view showing a method of temporarily attaching a lead frame, a brazing material, and a package body in another embodiment.

7 is a diagram showing a configuration and an operation of a main part in the temporary attachment in the embodiment of FIG. 6;

FIG. 8 is a cross-sectional view showing a configuration of a main part in a conventional brazing.

FIG. 9 is a plan view showing a configuration of a main part in a conventional brazing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lead frame 12 Brazing material 14 Work table 16 Laser emission unit 18 Base 20 Ceramic package main body 22 Guide pin

Claims (5)

[Claims] 1. A method of brazing a lead frame to a package conductor provided to be exposed on a main body of an electronic component package, wherein a predetermined brazing material is locally applied to a brazed portion of the lead frame by laser beam energy. Temporarily melting and temporarily attaching; and aligning and overlapping the lead frame temporarily attached to the package conductor with the brazing material interposed therebetween; and heating and dissolving all or most of the brazing material by heating. And joining the lead frame to the lead frame. 2. The method according to claim 1, wherein the step of temporarily attaching includes a step of superposing the brazing material on a brazing portion of the lead frame, and a step of irradiating the laser beam near a boundary between the brazing material and the lead frame. The lead frame brazing method according to claim 1, comprising: 3. The lead frame brazing method according to claim 2, wherein in the laser light irradiation step, a center of a beam spot of the laser light is aligned with the boundary. 4. A method of brazing a lead frame to a package conductor exposed on a main body of an electronic component package, wherein the lead frame is positioned and overlapped with a predetermined brazing material sandwiched between the package conductors. A step of locally dissolving the brazing material with the energy of laser light to temporarily attach the lead frame to the package conductor; and dissolving all or most of the brazing material by heating to form the package conductor and the leads. Joining the frame to the lead frame. 5. The method according to claim 1, wherein the temporary attaching step includes a step of irradiating a laser beam to one side or a peripheral surface of the brazing material through a gap between the electronic component package body and the lead frame. 5. The lead frame brazing method according to 4.