JPS6310477A - Soldering terminal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to soldering terminals in electronic devices, and particularly to materials suitable for soldering terminals in minute parts called micro soldering.

[Conventional technology]

Conventionally, soldering terminals have been soldered either by using Cu (copper) or At (aluminum) wiring as is, or by coating the surface of the wiring 30 with a wettability improvement layer 4 such as Au (gold) as shown in Fig. 2. Many materials with improved wettability are used.

In particular, most minute terminals have a structure in which Cu wiring is coated with Au. This structure is common because the specific resistance of CuQ is small and the adhesion of Cu to solder is good.

CC is an application of the aforementioned terminal structure in which Cu wiring is coated with Au to minute connections such as connections between IC chips and substrates.
This is the connection called B.

Review of the Electrical Communication Laboratories Volume 26, Issues 5-6 (197
8th year)% page 747 (Review of the F
! 1e-critical Communication
Laboratories, vol 26.

5-6 (1978), p, p, 735-747), it is indicated that a solder connection terminal having the structure as shown in Fig. 3 is used.Recently, the components of Fig. Generally, Rh (rhodium) in connection 1 is replaced with Cu to reduce material costs. In addition, in Figure 3, A
The u layer 4 is a solder wettability improving layer, and is made of Cr (chromium'
)H47 is an adhesive layer for improving the adhesive force between the wiring 3 and the adhesive layer 6.

In such a structure, when PB (lead)-9N (tin) soldering is performed, Sn is the fourth component of this solder component.
They are bonded and electrically conductive in the state shown in Figure (a).

However, if the connection is reheated after soldering, Sn
As the diffusion progresses, the solder diffusion region 9 may reach the adhesive layer 7 or the wiring 3 as shown in FIG. 4(b).

Usually, the metal used as the adhesive layer is a metal that is not compatible with Sn, such as Or or Mo (molybdenum), or a metal that forms a brittle compound with Sn. Therefore, it was necessary to form the connection layer 6 thickly (usually 3 to 4 μm) so that even if it reaches the adhesive layer, it does not reach the adhesive 1 even after the heat process in the 5ndZ working process.

However, if the connection layer 6 is thick, the connection layer is likely to crack depending on the application, and it takes time to form the connection layer and the material cost is high. Therefore, it is necessary to improve reliability and reduce material cost. was there.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology requires thickening of the connection layer in order to stop the solder diffusion in the middle of the connection layer, use of an expensive metal such as Rh, and consideration of the juxtaposition of such a configuration. It has not been. Therefore, in the above-mentioned conventional technology, it was necessary to reduce the cost of soldering terminals and improve connection reliability after soldering.

The object of the present invention is achieved by providing a structure in which solder diffusion is stopped midway through without increasing the thickness of the connection layer of the soldering terminal.

[Means for solving the problem] The above object is achieved by using an alloy of Cu and MO as the solder connection terminal in a CCB connection or a connection by soldering such as a lead wire. The Cu-Mo alloy has a Mo content of 0.1 to 50 molt, and the remainder 99.9 to 5 molt.
0% MoMo content is preferably 1 to 25%. Then, on the surface of the above Cu-Mo alloy, Au (
It is more preferable to coat gold). Further, the solder connection terminal of the present invention reduces manufacturing cost and improves solder connection reliability.

That is, the above object can be best achieved by changing the material properties of the layer (connecting layer) that undergoes solder diffusion and adjusting the rate of diffusion in the film thickness direction during the thermal process to an appropriate level.

In order to have an appropriate diffusion rate, it is necessary to use a material for the connection layer that has an appropriate diffusion rate for the component metals of the solder (for example, Sn and Pb).

In the case of normal 5n-Pb solder, Sn diffusion dominates the solder connection. The activation energy required for Sn diffusion in various metals is compared and shown in the following table.

When actually conducting a solder diffusion experiment using a Cu film, it was found that 5n
- When using Pb-based eutectic solder at 250°C % 0.1μ
Diffusion proceeds at a speed of m/@. In the case of N1, which has a large activation energy for υ diffusion, it is 0.001 μm7, which is less than 1/100 the speed of Cu. Therefore, even if a Cu thickness of 4 μm is required, the thickness of Ni is 40 μm.
It can be seen that it is very effective in thinning the terminal metal layer, since it only requires a thickness of about nm. However, the slow rate of diffusion means that it is difficult for the solder to penetrate into the terminal gold layer, and it requires high temperatures or a long time to make a connection, which poses a problem in the process. Not only that, but it can also occur if the connection is insufficient. Therefore, a material that quickly diffuses during connection and hardly diffuses thereafter is suitable as a terminal material.

In order to satisfy such contradictory functions, it would be impossible to use a single metal, so we investigated alloys.

The problem here is that if alloyed unnecessarily, the formation of intermetallic compounds may result in embrittlement or completely different properties against diffusion. Therefore, a Cu-Mo alloy was investigated as an alloy free from such a fear. This type of combination is usually a combination in which neither liquids nor solids mix, but a mixed thin film can be easily formed by sputtering or vapor deposition. The composition of this alloy film is such that Mo grains 10 are floating in Cu 11, as shown in FIG. Sn also has the property of not being mixed with MO, so Sn is mixed with Cu around MO to avoid MO.
A solder diffusion region 11 is formed by diffusing the inside.

For this reason, the distance over which Sn actually diffuses increases several times or more. Therefore, if a thickness of 4 μm is required for Cu.

In the case of a Cu-Mo alloy, a thickness of about 1 μm is sufficient.

Since almost pure Cu is exposed over a wide area on the surface of the Cu-Mo alloy, it has solder wettability comparable to that for Cu.

Such a combination is also used in an example in Nikkei Microdevice, No. 7 (1986), pages 145 to 153. In this example, an IC lead frame is manufactured using Cu and Cr, an alloy that hardly mixes with each other, and good results have been obtained by examining the diffusibility of solder. Further, in this example, since Cr is slightly dissolved in Cu, the specific resistance of the material is 1.2 to 1.3 times or more that of pure copper. However, since the combination of Cu and Mo does not have a solid solution range, the specific resistance can be approximately 1.1 times that of pure copper.

In addition, as mentioned above, the composition of the Cu-Mo alloy is Mol11
~50 molti, balance Cu is preferable, MocL1~20
Morti, the balance Cu is more preferable because MO is 5
This is because if the molarity exceeds 0, the solder wettability will drop sharply.

[Effect]

As mentioned above, in the Cu-Mo alloy, Mo is Cu
Since Sn becomes an obstacle to diffusion in the film, macroscopically, the diffusion rate of Sn becomes slow, and the required film thickness can be reduced. Furthermore,
Since Cu is almost pure Cu, it has good wettability with solder, and connection reliability does not deteriorate.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. Cu, A is deposited on a substrate 8 such as a glass substrate, a ceramic substrate, a resin substrate, etc. by a method such as sputtering, vapor deposition, or plating.
A wiring layer 3 made of T, Ni, Mo, W, etc., an adhesive #7 made of CrMo, etc. are formed, a Cu-Mo alloy layer 6 is formed by vapor deposition, sputtering, etc., and solder wettability made of Au is improved. Layer 4 was formed by vapor deposition, sputtering, plating, etc. At this time, in the formation of Cu-Mo alloy,
There are methods such as using a simultaneous vapor deposition (sputtering) method in which Cu and Mo are separately and simultaneously vapor-deposited or sputtered, or cis sputtering using a target in which Cu plates and Mo plates are arranged alternately to have a predetermined area. Either film can be formed easily and at high speed. After the film formation was completed, the Nu layer and the Cu--Mo layer were sequentially patterned by photoetching. At this time, Au and Cu-Mo are simultaneously etched with aqua regia, or only the surfaces of Au and Cu-Mo are etched with an iodine-based solution and the remaining Cu-Mo is etched with a nitric acid-based etching solution. Cu-Mo itself can be easily etched with an oxidizing acid (nitric acid, etc.). Thereafter, the adhesive layer 7 and the wiring layer 3 are patterned by photoetching. In the above example, the adhesive layer 7 may be omitted depending on the material of the wiring layer 3. The wiring layer can also be formed using thick film technology such as printing and baking. Furthermore, if process control is performed to prevent oxidation of the surface of the Cu--Mo layer, the Au layer can also be omitted, thereby reducing costs.

〔Effect of the invention〕

As described above, according to the present invention, the connection layer required for soldering can be made as thin as around 1 μm, which improves reliability by eliminating large steps, improves the connection strength of the connection, and reduces the time required to form the connection. By shortening the length and reducing the amount of materials used, the cost of soldering terminals is reduced. Furthermore, by changing the blending ratio of Cu and Mo, it becomes possible to control the solder diffusion rate, which increases the degree of freedom in design. Also,
Specific impulse is almost the same as purity.

[Brief explanation of drawings]

Figure 1 is a diagram showing the soldering terminal of the present invention, Figure 2 is a diagram showing the structure of a conventional soldering terminal, and Figure 3 is a CCB.
A diagram showing a conventional example of connection, FIG. 4(a) is a diagram showing a state of solder connection in a conventional structure, FIG. 4(b)
A diagram showing the progress of diffusion due to a thermal process after soldering connection, FIG. 5 is a diagram showing the structure of the Cu-Mo alloy used in the present invention,
FIG. 6 is a diagram showing an embodiment of the present invention. 1... Composition range according to claim 1 of the present patent 2...
Composition range according to claim 2 of this patent 3...Wiring 4...Wettability improving layer 5...Solder 6...Connection layer 7...Adhesive layer 8...Substrate 9...Solder Diffusion region 10...Mo (molybdenum) 11...Cu (copper). Figure 1 ? 30th 4-zu demand J) L8 raw improvement waste 5・-1;
Poetry, 47. -Dentsuta 4 Figure 4

Claims (1)

[Claims] 1. A soldering terminal characterized by being made of a Cu-Mo alloy. 2. The Cu-Mo alloy contains Mo0.1 to 50 mol%,
Cu- having a composition consisting of 99.9 to 50 mol% Cu
The solder connection terminal according to claim 1, which is made of a Mo alloy. 3. A soldering terminal made of a Cu-Mo alloy, and characterized in that an Au layer is provided on the surface of this alloy. 4. The Cu-Mo alloy contains 0.1 to 50 mol%, Cu9
The solder connection terminal according to claim 3, which is a Cu-Mo alloy having a composition of 9.9 to 50 mol%.