JPH0543476Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a post cream solder application pattern for wire bonding.

[Summary of the invention] The present invention reduces the inclination of the post by applying the cream solder coating pattern of the soldering pad to which the wire bonding post is soldered so that it does not apply at least to the part corresponding to the center of the post. The aim is to prevent

[Prior Art] Conventionally, aluminum posts have been used as bonding pads for wire bonding, for example in hybrid integrated circuits.

FIG. 4 shows a ceramic substrate for such a hybrid integrated circuit, and the ceramic substrate 10 has a large part 1.
1 and two small soldering pads 12 are provided, and a transistor chip 20 having a heat sink 21 is mounted on the soldering pads 11. Further, an aluminum post 40 is soldered to both soldering pads 12, and the transistor chip 2 is connected to the aluminum post 40.
An aluminum wire 41 is wired between 0 and each aluminum post 40. Soldering part 12 is the fifth
As shown in the figure, it has a square shape, and cream solder 13 is applied thereon in a square shape except for the periphery. As shown in FIG. 6, the aluminum post 40 has a lower bonding surface 42 having a substantially spherical shape, and this bonding surface 42 and the soldering pad 12 are soldered with cream solder 13.

[Problem to be solved by the invention] Such an aluminum post 40 is soldered by reflow soldering, but since the specific gravity of the aluminum post 40 is lighter than that of solder, it floats up and becomes tilted as shown in Fig. 6. It gets attached.
If the aluminum wire 41 is bonded to the aluminum post 40 tilted in this way using a wire bonder, the bonding will not be performed correctly and the adhesive strength between the aluminum post 40 and the aluminum wire will be weakened.
Further, there is a problem that the strength of the aluminum wire itself becomes weak.

The present invention was made with the aim of solving these problems.

[Means for Solving the Problem] The cream solder application pattern for a post according to the present invention is such that in a part for soldering a post whose soldering surface is approximately spherical, the cream solder corresponds to at least the center portion of the post. It is characterized in that it is applied to all but the body parts.

[Function] Since the present invention has the above-described structure, the bonding surface of the post is evenly supported from the surrounding area by the cream solder and soldered in a balanced state, so that the inclination of the post is extremely small. Become.

[Embodiment] FIG. 1 shows a pattern of applying cream solder to a soldering pad 12 according to an embodiment of the present invention. Each cream solder 14 has a small square shape, and is arranged evenly and symmetrically on the soldering pad 12 in a substantially square shape.

Therefore, since the cream solder is not applied to the center of the soldering pad 12, when the aluminum post 40 is placed on the soldering pad 12 and reflow soldering is performed, the cream solder 14 is applied to the aluminum post 40. Since the peripheral part of the bonding surface 42 is evenly supported while avoiding the center part, the aluminum post 40 is soldered without tilting.

The cream solder application pattern is not limited to the one in which squares are arranged in a square shape as shown in Fig. 1, but also the cream solder 15 in the shape of a square with notched corners as shown in Fig. 3A. By arranging them in a shape, the area of the central portion that is not soldered with cream may be increased.

Also, cream solder is not limited to square-shaped solders.
Multiple fan-shaped cream solders 16 as shown in Figures B and C,
17 may be arranged in a substantially donut shape.

[Effects of the invention] As described above, according to the invention, since the cream solder is applied avoiding the central part, the post 40 is soldered without tilting, and the bonding surface becomes horizontal, so that the wire to be bonded is bonding strength increases.

[Brief explanation of the drawing]

Fig. 1 is a top view showing the shape of cream solder on a soldering pad showing an embodiment of the present invention, Fig. 2 is a cross-sectional view showing its usage state, and Fig. 3 A, B, and C are each of the embodiments of the present invention. A top view showing another embodiment, FIG. 4 is a sketch showing a ceramic substrate to which the present invention can be applied, FIG. 5 is a top view showing the shape of cream solder in a conventional patch, and FIG. FIG. 10... Ceramic board, 12... Soldering parts, 13, 14, 15, 16... Cream solder,
40...Aluminum post, 41...Aluminum wire.

Claims (1)

[Scope of utility model registration request] This cream solder application pattern for a post is characterized in that in a pad for soldering a post having a soldering surface made approximately spherical, the cream solder is applied at least except for a portion corresponding to the center of the post.