JPH1065041A - Formation of spherical terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form spherical terminals corresponding to a fine pitch and to easily perform measuring test as to electric characteristics before surface mounting thereof in the case where the spherical terminals for the surface mounting are formed. SOLUTION: A pin-type terminal 1, consisting of high melting point solder 3, whose one end has low melting point solder 2 joined thereto is erected on a pad 5 formed on the surface of a base 4 by fusing the low melting point solder 2, then the pin-type terminal 1 consisting of high melting point solder 3 is heated and fused to be deformed owing to surface tension to form a spherical terminal 6. The difference between the low melting point of 2 and the high melting point is not less than 20 deg.C. Thus, the measuring test as to electric characteristics can easily be carried out in a state wherein the pin-type terminal 1 is erected, and then surface mounting can easily be performed as the spherical terminal 6. Further, the spherical terminals can easily cope with a fine pitch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a spherical terminal used when a semiconductor element is mounted on a semiconductor element housing package or a semiconductor element housing package is mounted on a circuit board.

[0002]

2. Description of the Related Art When a surface-mount type semiconductor element housing package housing a semiconductor element such as an LSI (large-scale integrated circuit element) is mounted on a circuit board, the mounting terminal is a main surface of a package base. A pin-shaped terminal using a metal pin or a spherical terminal using a spherical metal such as a so-called solder bump, which is connected to a terminal portion formed and arranged in a matrix, is usually used. (Pin grid array) type, and the latter is called BGA (ball grid array) type.

In general, a PGA type mounting terminal can easily perform an electrical characteristic measurement test by inserting a pin-shaped terminal into a socket or the like. However, the pin-shaped terminal is accurately inserted into a large number of insertion holes on the circuit board side. Since it is difficult to insert, it tends to be difficult to perform surface mounting. On the other hand, the mounting terminals of the BGA type have a large number of terminals (lands) on the circuit board side.
It is easy to perform surface mounting because it is only necessary to heat and melt the spherical terminal while the spherical terminal is in contact with
In order to obtain good electrical connection only by contact with the spherical terminal, a large load is required on the spherical terminal and the package body, so that the socket for the measurement test becomes complicated and the durability of the spherical terminal is problematic due to the measurement. Tends to be difficult to occur.

[0004] In response to the progress of high integration and miniaturization of semiconductor elements and circuit boards, the density of mounting terminals has been increased, the pitch between mounting terminals has been narrowed, and fine pitch has been advanced. Flip chip mounting, which is advantageous for high integration and miniaturization, is becoming mainstream for mounting a semiconductor element storage package on a circuit board. BGA type spherical terminals are suitable for this flip chip mounting. However, it is difficult to supply spherical metal and arrange the spherical terminals with high precision and high density to form spherical terminals corresponding to fine pitch. It is more difficult than arranging pin-shaped terminals by supplying metal pins.

[0005]

As a method of forming a spherical terminal for surface mounting, a method of printing using a solder paste and a method of dipping (immersion) in a solder bath have been conventionally used.
Many methods are known, such as a soldering method, a solder plating method, and supplying a solder ball using a mask. However, any of these methods has a problem that it is difficult to form a desired spherical terminal by supplying a sufficient amount of solder with good mass productivity while preventing a short circuit between terminals corresponding to a fine pitch. Was.

Further, even when a spherical terminal is used as a mounting terminal of a package for storing a semiconductor element, the electrical characteristics of the package for storing a semiconductor element do not deteriorate the durability of the mounting terminal before surface mounting. There was also a demand that the measurement test be easily performed.

Further, the above-mentioned problems and demands are caused not only in the package for housing the semiconductor element but also in the surface mounting of the semiconductor element on the mounting portion of the package for storing the semiconductor element, or in the case of other circuit boards in the circuit board. The same applies to the case where a spherical terminal is used for surface mounting on a device.

The present invention has been devised in view of the problems and demands of the prior art, and has the following objects.
As a fine-pitch mounting terminal, a sufficient amount of solder can be supplied with good mass productivity while forming a short circuit between the terminals to form a desired spherical terminal, and the durability of the mounting terminal is reduced before surface mounting. It is an object of the present invention to provide a method of forming a spherical terminal that can easily perform a measurement test of electrical characteristics without using the terminal.

[0009]

According to the method of forming a spherical terminal of the present invention, a pin-shaped terminal made of a high-melting-point solder having a low-melting-point solder joined at one end is melted with the low-melting-point solder. Then, the pin-shaped terminal made of the high melting point solder is heated and melted and deformed into a spherical shape by surface tension.

The method of forming a spherical terminal according to the present invention is a method of forming such a spherical terminal, wherein the difference between the melting point of the low melting point solder and the melting point of the high melting point solder is 20 ° C. or more. It is characterized by the following.

[0011]

According to the method of forming a spherical terminal of the present invention, first, a pin-shaped terminal made of a high-melting-point solder having a low-melting-point solder joined at one end is melted with the low-melting-point solder to form a substrate surface. In this state, the mounting terminals have the same shape as that of the PGA type, and the terminals in this state are inserted into a socket or the like so as to be electrically connected without lowering the durability of the mounting terminals. A characteristic measurement test can be easily performed. Further, since the pin-shaped terminals are erected on the pads formed on the surface of the base, even if the arrangement pitch of the pads, that is, the pitch between the mounting terminals is narrow, the mounting terminals can be easily and accurately arranged, It can easily cope with fine pitch of mounting terminals.

Further, according to the method of forming a spherical terminal of the present invention, after the pin-like terminal is erected in this manner, the pin-like terminal made of a high melting point solder is melted by heating and deformed into a spherical shape by surface tension. Therefore, in this state, BG
It becomes a mounting terminal of the same shape as the A type, and it can be easily mounted on the surface by heating and melting it in a state where the terminals are in contact with a large number of terminals (lands) on the mounting circuit board side. Become. In addition, the pin-shaped terminals, which are erected accurately on the pads on the surface of the base, are heated and melted and deformed into a spherical shape. A desired BGA type spherical terminal corresponding to the pitch can be formed.

Further, according to the method of forming a spherical terminal of the present invention, the difference between the melting point of the low melting point solder and the melting point of the high melting point solder of the pin-shaped terminal composed of the high melting point solder having one end joined to the low melting point solder. Since the temperature is set to 20 ° C or higher, even when a large number of pin-shaped terminals are supplied at one time and are erected on the pads on the surface of the base, the pin-shaped shape must be deformed without melting the high melting point solder. In addition, only the low-melting-point solder can be melted and fused to the pads to be erected, and a large number of mounting terminals can be formed stably and accurately even in mass production.

Hereinafter, the present invention will be described with reference to the accompanying drawings. 1A to 1C are cross-sectional views showing an example of an embodiment of a method for forming a spherical terminal according to the present invention. FIG.
(A) is a cross-sectional view showing an example of a pin-shaped terminal, in which 1 is a pin-shaped terminal, which is composed of a high-melting-point solder 3 to which a low-melting-point solder 2 is joined at one end.

As the low melting point solder 2, for example, 63 wt% Sn / 37 wt% Pb (melting point: 183 wt.
° C), 46 wt% Sn / 46 wt% Pb / 8 wt% Bi (melting point 180 ° C), or 43 wt% Sn / 43 wt% Pb / 14
A so-called low melting point solder such as wt% Bi (melting point 140 ° C.) is used.

On the other hand, as the high melting point solder 3, for example, 10
wt% Sn / 90wt% Pb (melting point 300 ℃) or 5wt% Sb
A so-called high melting point such as n / 95 wt% Pb (melting point 340 ° C.) is used.

The volume ratio of the low melting point solder 2 to the high melting point solder 3 in the pin-shaped terminal 1 is preferably about 1:10 to 1:20 for the low melting point solder and the high melting point solder. Is preferable in that the bonding strength is good when they are melted. The dimensions of the pin-shaped terminal 1 are
It is preferable that the pin-like terminal 1 is about 0.35 to 0.55 mm and the length is about 2 to 4 mm because the pin-like terminal 1 is easily inserted into the socket and the pin-like terminal 1 is hardly deformed when inserted into the socket.

FIG. 1B is a cross-sectional view showing a state in which the pin-shaped terminals 1 are erected on pads formed on the surface of the substrate. In FIG. Pads as mounting electrodes.

The base 4 may be, for example, an insulating base of a semiconductor element storage package surface-mounted on a mounting circuit board, a semiconductor element substrate mounted on a mounting portion of the semiconductor element storage package, or mounted on a mounting circuit board. Circuit board to be used. As the insulating base of the package for housing semiconductor elements, for example, ceramics such as aluminum oxide sintered body, mullite sintered body, silicon carbide sintered body, aluminum nitride sintered body, or glass ceramic sintered body, Alternatively, various insulating plastics such as glass epoxy resin and BT resin are used. For a semiconductor element substrate, for example, silicon or gallium arsenide is used. For a circuit substrate, for example, a ceramic or resin substrate is used. Is used.

The pad 5 is formed of W, Mo.Cu, or the like, and by subjecting them to Ni / Au plating or the like. The array is formed at a pitch of 1.27 mm, for example.

The above 43 wt% Sn / 43 wt% Pb / 14 wt% B
i (melting point 140 ° C) low melting point solder 2 is 10wt% Sn / 90wt
When the pin-shaped terminal 1 (difference in melting point: 160 ° C.) joined to the high melting point solder 3 having a melting point of 300% Pb, the peak temperature is set to about 190 ° C. and the low melting point solder 2 is padded. 5, the pin-shaped terminal 1 can be erected as shown in FIG. 1B without melting only the low melting point solder 2 and melting and deforming the high melting point solder 3.

The condition for standing up in this manner is to keep the temperature at about 140 to 200 ° C. for about 30 seconds to 2 minutes in consideration of the shape of the fillet formed by the low melting point solder 2 and the like. do it.

At this time, when the difference between the melting point of the low melting point solder 2 and the melting point of the high melting point solder 3 becomes smaller than 20 ° C., when the low melting point solder 2 is melted, the high melting point solder 3 is deformed. Since the pin shape tends to be difficult to maintain, the difference in the melting points is preferably 20 ° C. or more. On the other hand, the upper limit of the difference in the melting point is determined by the high melting point solder 3 and the low melting point solder 2 used for the pin-shaped terminal 1, and does not have to be lower than the lower limit.

By inserting the pin-like terminal 1 in this state into a socket or the like of a pin insertion type, a measurement test of electrical characteristics can be easily performed without reducing the durability of the pin-like terminal 1 as a mounting terminal. I can do it.

Further, a fine pitch is formed on the surface of the substrate 4 by a method such as inserting a large number of pin-shaped terminals 1 into a plate jig provided with holes into which the pin-shaped terminals 1 can be inserted at the same pitch as the pin terminals. Since the plurality of pads 5 can be provided upright, even if the pitch between the mounting terminals is narrow, it is possible to easily and accurately arrange a large number of pin-shaped terminals 1 to cope with the problem.

FIG. 1C is a sectional view showing a state in which the pin-shaped terminal 1 erected on the pad 5 is heated and melted and deformed into a spherical shape by surface tension. In FIG. Are spherical terminals formed on the pad 5.

The above 43 wt% Sn / 43 wt% Pb / 14 wt% B
i (melting point 140 ° C) low melting point solder 2 is 10wt% Sn / 90wt
When the pin-shaped terminal 1 (difference in melting point: 160 ° C.) joined to the high melting point solder 3 of% Pb (melting point 300 ° C.) is erected on the pad 5, the reflow is performed at a peak temperature of about 350 ° C. By heating in a furnace, the high melting point solder 3 is melted and deformed into a spherical shape on the pad 5 by its surface tension, so that a spherical terminal 6 can be formed as shown in FIG.

At this time, the low-melting-point solder 2 is melted together with the high-melting-point solder 3, and the two kinds of solder are mutually diffused to form a spherical terminal 6 having a substantially uniform solder composition on the pad 5.

Therefore, the low melting point solder 2 and the high melting point solder 3
Is desirably selected in consideration of the characteristics required for the spherical terminal 6 that is melted and becomes a substantially uniform composition.

As a heating and melting means or method for deforming the pin-like terminal 1 into a spherical shape, a method of mounting on a heater block and a method of heating in a batch furnace besides using a reflow furnace. and so on.

The conditions for the heating and melting are, for example, about 350 ° C. in a nitrogen atmosphere in consideration of the fact that the pin-shaped high melting point solder 3 is deformed into a spherical shape by surface tension.
For about one minute.

As a result, the spherical terminal 6 becomes a mounting terminal having the same shape as the BGA type, and is heated and melted while the spherical terminal 6 is in contact with a large number of terminal portions (lands) on the mounting circuit board. Surface mounting can be easily performed. Moreover, since the pin-shaped terminals 1 erected on the pads 5 on the surface of the base 4 with high precision are melted by heating and deformed into spherical shapes, a sufficient amount of solder can be supplied with good mass productivity while preventing short-circuiting between the terminals. Thus, a desired BGA type spherical terminal 6 corresponding to the fine pitch can be formed.

Further, since the difference between the melting point of the low melting point solder 2 and the melting point of the high melting point solder 3 of the pin-shaped terminal 1 is set to 20 ° C. or more, a large number of pin-shaped terminals 1 are supplied at one time to Even in the case of standing on the pad 5 on the front surface, only the low-melting-point solder 2 is melted without melting the high-melting-point solder 3 and deforming the pin-like shape, and is fused to the pad 5 to stand. Thereafter, the step of heating and melting the pin-shaped terminal 1 and deforming the pin-shaped terminal 1 by surface tension to form the spherical terminal 6 can be stably performed.
Even during mass production, a large number of spherical terminals 6 can be formed stably and accurately.

It should be noted that the present invention is not limited to the above-described embodiment, and that various changes and improvements can be made without departing from the scope of the present invention.

[0035]

According to the method for forming a spherical terminal of the present invention,
First, a pin-shaped terminal made of a high-melting-point solder having a low-melting-point solder joined to one end thereof is erected on a pad formed on the surface of the base by melting the low-melting-point solder. Therefore, by inserting the terminal in this state into a socket or the like, a measurement test of electrical characteristics could be easily performed without reducing the durability of the mounted terminal. In addition, since the pin-shaped terminals are erected on the pads formed on the surface of the base, even if the pitch between the mounting terminals is narrow, the mounting terminals can be easily and accurately arranged, and the fine pitch of the mounting terminals can be easily achieved. I was able to respond.

Further, according to the method of forming a spherical terminal of the present invention, the pin-shaped terminal made of high melting point solder is heated and melted after the pin-shaped terminal is accurately erected in this manner, and the pin-shaped terminal is formed into a spherical shape by surface tension. Since it is deformed, a spherical terminal having the same shape as the so-called BGA type can be easily formed in correspondence with a desired fine pitch by supplying a sufficient amount of solder with good mass productivity while preventing a short circuit between the terminals. I was able to. As a result, surface mounting on the terminal portion (land) on the mounting board side can be easily performed.

Further, according to the method of forming a spherical terminal of the present invention, since the difference between the melting point of the low melting point solder and the melting point of the high melting point solder of the pin-shaped terminal is set to 20 ° C. or more, a large number of pins can be formed at one time. Even if the terminal is supplied and it is erected on the pad on the surface of the base, only the low melting point solder is melted and fused to the pad without melting the high melting point solder and deforming the pin shape. The mounting terminals could be erected, and a large number of mounting terminals could be formed stably and accurately even during mass production.

Therefore, according to the present invention, the surface mounting of the semiconductor element housing package on the circuit board, the surface mounting of the semiconductor element on the mounting portion of the semiconductor element housing package, or the mounting of the circuit board on another circuit board is performed. When using spherical terminals in surface mounting etc., it is possible to form a desired spherical terminal by supplying a sufficient amount of solder with good mass productivity while preventing short circuit between terminals as a fine pitch mounting terminal,
In addition, a method for forming a spherical terminal that can easily perform a measurement test of electrical characteristics without reducing the durability of the mounted terminal before surface mounting can be provided.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views each showing an example of an embodiment of the present invention.

[Explanation of Signs] 1 ... Pin-shaped terminal 2 ... Low melting point solder 3 ... High melting point solder 4 ... Base 5 ... Pad 6 ... ..Spherical terminals

Claims (2)

[Claims] 1. A pin-shaped terminal made of a high-melting-point solder having one end joined with a low-melting-point solder is erected on a pad formed on the surface of a base by melting the low-melting-point solder. A method for forming a spherical terminal, wherein a pin-shaped terminal made of a melting point solder is heated and melted and deformed into a spherical shape by surface tension. 2. The method according to claim 1, wherein a difference between a melting point of the low melting point solder and a melting point of the high melting point solder is 20 ° C. or more.