JPS6133789A - Solder alloy for connector junction - Google Patents

Abstract

PURPOSE:To stabilize the contact with the metallic pins of a semiconductor module by using a solder alloy constituted by adding a specific ratio of Au to an In-Sn alloy having a prescribed compounding ratio for the solder alloy to be packed into a connecting tank of a solder melting type high-density connector. CONSTITUTION:The solder alloy formed by adding Au to the In-Sn alloy consisting of 41-93wt% In and the balance Sn at 0.1-19.5wt% by the total weight of said alloy is packed into the connecting tank for the solder melting type high- density connector, by which the packaging of the semiconductor element to a printed board is executed. The contact with the metallic pins of the semiconductor module is thus stabilized and the life of the metallic pins is considerably extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the composition of a solder alloy filled in a connection tank of a solder melting type high-density connector.

rc as a way to improve the processing power of a computer.

Semiconductor chips such as LSIs are becoming smaller in size and larger in capacity, but at the same time improvements are being made in mounting methods.

That is, in the past, a mounting method was adopted in which chips such as ICs and LSIs were mounted on a ceramic substrate with multilayer wiring and hermetically sealed, and a large number of such semiconductor elements were mounted on a printed wiring board.

However, in the future, with the improvement of moisture-resistant processing technology, multiple I and Sr chips will be mounted on a multilayer ceramic wiring board to create an LSI module, which will be used as a replacement unit, and connected via a connector. A mounting form of mounting on a printed wiring board is now being adopted.

In this case, the connector is fixed to the printed wiring board by a method such as soldering, while the LSI module can be inserted into and removed from the connector.

Here, in order to attach a semiconductor element such as an IC or an LSI in a removable state, conventionally, a connector consisting of a tAt contact and a female contact has been used for connection.

That is, a plurality of metal pins protrude from the back side of a semiconductor package such as an IC or an LSI to form a male contact, while a female contact is a contact mechanism equipped with a spring, thereby forming a connector.

In the case of such a conventional connector structure, a load of several tens of grams per terminal is required for insertion and removal, and the number of terminals is several hundred grams like the connector used for the LSIS terminal according to the present invention in (ifi-). If this method is applied to a multi-terminal contact mechanism, a load of several kilograms will be required for insertion and removal, and insertion and removal cannot be performed by normal means.

Therefore, a solder melt type connector has been proposed as a method to solve this problem.

In other words, this connector allows terminals to be inserted and removed under conditions close to zero insertion force and zero removal force, and the contact mechanism consists of an M contact made of a metal pin and a female contact whose connection tank is filled with a low melting point metal such as solder. During insertion and removal, the connection tank is heated to melt the low melting point metal, and in this state, male contacts made of metal pins are inserted and removed, thereby connecting the connector with almost zero insertion and removal force.

The connection tank is kept at room temperature except during insertion and removal, and the 1L
The low melting point metal forming the ull contact is firmly attached to the metal pin forming the m contact, achieving a contact resistance close to zero.

The present invention relates to the composition of the solder alloy to be filled into the connection tank of the T11 melting type high-density connector.

[Prior Art] There are various types of low melting point metals that are filled in the connection tank of solder melting type high density connectors, but indium (In)-tin (Sn) alloys are typical, and they have melting points of 117 to 117. 1
It is said that a 50° C. In-formed material is suitable.

Figure 2 shows a phase diagram of the In-Sn alloy system, and the composition that melts in this temperature range is the diagonally shaded area 1, which is downward to the right, where the Sn content is 7 to 59% by weight, or 41 to 93% by weight. This is the composition of In and remaining Sn.

The reason why the upper limit is set at 150°C is that the high-density connector is attached to the print 1 to wiring board using normal 6-4 solder (3
7Pb-63Sn (melting point 183°C) is used, so the solder alloy filled in the connection tank must be melted at a temperature below this temperature.
The temperature was set at 50°C.

Further, the reason why 117° C. is taken as the lower limit is that this temperature is the eutectic temperature, as is clear from the phase diagram.

Conventionally, solder alloys having such alloy compositions have been used.

However, since this alloy has low hardness, contact with the metal pin forming the male contact is unstable during use, which poses a problem in ensuring reliability.

[Problem to be Solved by the Invention 3 As mentioned above, In-Sn alloy is suitable for the solder melting type connector according to the present invention because of its low melting point.
The unstable contact with the metal pins of the semiconductor module is a problem from the viewpoint of ensuring reliability, and the purpose of the present invention is to
The objective is to improve the -5n solder alloy to obtain a stable contact state.

[Means for solving problems]

The above-mentioned problem is that the solder alloy filled in the connection tank of the solder melting type high-density connector is 41 to 93% by weight of In and the rest is Sn, and the gold (Au) is equivalent to 0.1 to 19.5% by weight of the total amount. ) can be solved by using a product with added.

[Effect]

The present invention uses A as an additive that has a melting point in the insertion/extraction temperature range of 100°C to 150°C for In-Sn alloys, has high hardness, and does not cause an increase in contact resistance with metal pins.
n is found, and by adding 0.1 to 19.5% by weight of the total amount, the problem described in "-" can be solved.

The inventors previously discovered that when silver (Ag) was added to an In-Sn alloy system, the hardness increased, which stabilized the contact with the metal pin, and a similar phenomenon occurred when Au was added. It has also been found that the life of metal pins can be significantly improved by using a ternary alloy system to which Au is added.

〔Example〕

FIG. 1 shows a cut state diagram of the ternary alloy according to the present invention, and shows the case where Au is added to the eutectic composition of 521n-48Sn.・As you can see from the figure, by adding 5% by weight, the eutectic temperature of 117°C becomes 115
．． 5'c, and thereafter the liquidus line 2 tends to gradually rise as the amount added increases.

Here, if the upper limit of the operating temperature of the In-3n alloy is determined to be 150 DEG C. as described above, then the upper limit of the addition of AL1 is 19.5% by weight from FIG.

As shown in the figure, the in-phase line 3 also decreases to 114.2° C. by adding 5% Au, and thereafter maintains a substantially constant value regardless of the amount added.

Figure 3 shows the change in Knoop hardness measured at room temperature for the alloy composition shown in the cutting diagram shown in Figure 1.The horizontal axis shows the amount of addition, with the case of Au addition and the case of Ag addition. In contrast.

That is, the Knoop hardness of the eutectic composition is approximately 1.1, but the hardness increases in proportion to the amount added.

When Ag is added here, 4 increases rapidly in proportion to the amount added, and tends to be saturated after about 10%, but An
When adding 5, it increases almost linearly, and when the amount added is 20
%, there is still no tendency to saturation.

FIG. 4 shows changes in contact resistance with a metal pin measured at different temperatures using a solder alloy whose hardness has been increased by adding Au, and is compared with the case of adding Ag.

Here, the metal pin uses a phosphor bronze wire with a diameter of 0.3 tuna as the core wire,
This was coated with nickel (Ni) to a thickness of 2 μm and palladium (
Pd) was plated as a 2 μm base plate, and then a 0.1 μm layer was plated on top of this.
It is plated with Au to a thickness of .

Two such metal pins were inserted into a solder alloy bath and solidified, and the change in resistance value between the two metal pins was measured by varying the temperature.

Here, the solder alloy has a eutectic composition, that is, 521n 48S
The cases of a solder bath 6 of n, a solder bath 7 in which 5% by weight of Au is added to the eutectic composition, and a solder bath 8 in which 5% by weight of Ag is added are shown.

As can be seen from the figure, when the conventional solder bath 6 with a eutectic composition is used, the contact resistance value is about 1.8 mΩ, indicating an unstable contact state, but when the solder bath 7 containing Au and the Ag
When using the solder bath 8 to which is added, it is stable, and the contact resistance value is about 1.5 mΩ, which is lower than when using the solder bath 6 having a eutectic composition.

The above supports the assumption that contact instability when using conventional solder baths is due to insufficient hardness of the solder alloy, and that the problem can be solved by the Au-added ternary alloy according to the present invention. can.

A second advantage of using this ternary alloy as a solder bath is that it can extend the life of the metal pin.

In other words, metal pins are normally plated with Au to ensure reliability, but if they are repeatedly inserted into and removed from a molten solder bath, the Au atoms that make up the Au plating will dissolve into the solder bath. There is a problem in that the underlying metal is exposed and the reliability is reduced.

However, if a ternary alloy containing Au is used as a solder bath, dissolution of the Au plating can be significantly suppressed.

As an example, as described above, metal pins with a diameter of 0.3 nm and a length of IH plated with 0.1 μm of Au were prepared using three metal pins, one with 5% Au added to the eutectic composition and the other with Ag added. When we prepared a solder bath of the original alloy and conducted an immersion test while keeping it at 300°C, we found that in the case where the Ag-added bath was used, the All plating completely melted and left no trace after 100 hours. , 0.05 μm using Au addition bath
The plating film remained.

The superiority of the ternary alloy according to the present invention can be understood from the results of such severe tests.

Note that the claimed range specifies that the minimum amount of Au added is 0.1%; the reason for this is that the amount added is 0.1%.
% or less, this is because almost no increase in hardness is observed.

〔Effect of the invention〕

As explained above, In-3n-Au according to the present invention
Using a solder alloy with a ternary alloy containing 0.1 to 19.5% of Au can solve the problems of unstable contact and melting of the plating film, which were problems with solder melting type high-density connectors. It can be solved.

[Brief explanation of drawings]

FIG. 1 is a cut-away diagram of the solder alloy for connector contacts according to the present invention. FIG. 2 is an In-3n binary phase diagram. FIG. 3 is a characteristic diagram showing changes in hardness when Au or Ag is added to an In-3n alloy. FIG. 4 is a characteristic diagram showing the temperature characteristics of contact resistance between a metal pin and a solder bath. It is. In the figure, 2 is the liquidus line, 3 is the solid phase cotton, and 4.8 is the Ag
5.7 is a solder bath to which AI+ is added. Four parts and

Claims (1)

[Claims] The solder alloy filled in the connection tank of the solder melting type high-density connector is an alloy of 41 to 93% by weight indium and the remainder tin.
A solder alloy for connector contacts, characterized in that gold is added in an amount corresponding to 0.1 to 19.5% by weight of the total amount.