JPH01274492A - Manufacture of substrate device using non-eutectic solder - Google Patents

Abstract

PURPOSE:To prevent the generation of the rising phenomenon of a surface mounting part by using non-eutectic solder and transporting a printed board carrying the surface mounting part in different temperature atmospheres. CONSTITUTION:An alloy selected in a solidus curve and a liquidus curve is employed as non-eutectic solder. Fixed quantities of the non-eutectic solder 10, 11 are applied onto specified conductive layers 6, 7 formed onto a printed board 5, and a surface mounting part 1 is fixed temporarily onto the top faces of these solder. The solder 10, 11 begins to be melted at a proper temperature Tc from a temperature T1 to a temperature T2 in a vapor phase type solder tank controlled at a first heating temperature regarding the printed board 5 under the state. When there is temperature difference between the electrode sections of the surface mounting part 1 at that time, the high temperature side between them is melted first. Since, however, surface tension by the half melting of solder 10 is extremely small, one side of the part 1 is not lifted by the surface force. When the substrate 5 is transported in the vapor phase type solder tank selected at a temperature higher than the liquid-phase temperature T2 regarding an ambient temperature, solder 11 under a half-melted state is also brought to a molten state, and the electrode sections 3 are fixed completely.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a board device in which a surface-mounted electronic component is fixed onto a Zolin board using a vapor phase soldering tank or the like. The present invention relates to a method of manufacturing a board device in which surface-mounted electronic components are fixed using non-eutectic solder.

[Prior art] In order to increase the mounting density of hybrid IC'Js, there is a tendency to use light, thin, short, and small surface-mounted components, such as chip-type capacitors, as the electronic components mounted on the IC board. .

In addition, the size and size of surface-mounted components are different, and the sizes and sizes of the same electronic components are different from each other.

Moreover, in order to mount such surface-mounted components, reflow soldering equipment often runs out of use.

As shown in 4th r2I, paste-like solder 8 is placed between conductive layers 6 and 7 formed on a predetermined printed circuit board 5.
．． 9 etc., the surface mount component 1 is temporarily fixed, and in the temporarily fixed state, the printed circuit board 5 is exposed to an infrared υ flow furnace or an air 4
'[] The solder is transported into a solder tank (not shown).

The paste solder 8, 9 is usually a high melting point solder, such as 5n-Pb eutectic solder (its melting point is 18
3°C) is used.

High temperature atmosphere in an infrared reflow oven or vapor phase soldering bath (18
By passing the printed circuit board 5 through the temperature (3° C. or higher), the paste solder 8 and 9 are melted, and the printed circuit board 5 is cooled by the subsequent feeding 1a. The melted solder is now solidified, and the surface mount component 1 is fixed onto the printed circuit board 5.

[Problem to be Solved by the Invention] By the way, as mentioned above, when the surface mount component 1 is mounted on the printed circuit board 5 using a soldering device such as an infrared reflow oven or a vapor phase soldering tank, the soldering All surface mount components 1 passing through the high temperature atmosphere inside the device are always -
It is not always possible to heat the food at different temperatures.

The shape and size of electronic components to be mounted vary, and small surface mount components adjacent to large surface mount components are affected by the large surface mount component, and This is because a temperature difference may occur even between the electrode parts 3° and 4.

If there is a difference in temperature like this, the paste solder 8
.

In this way, for example, if the paste solder 8 on the left side is completely melted and the paste solder 9 on the right side is incompletely melted, the completely melted paste solder 8 side is more likely to melt than the other paste solder 8 itself. surface tension increases.

This surface tension difference is caused by the blue electrode part 3 as shown by the arrow in FIG.
．． This appears as a difference in the moment (vertical component of the rotational moment) in the height direction at 4, and the moment applied to the electrode part 3 on the completely melted side is greater than the moment applied to the incompletely melted electrode part 4 side. It suddenly becomes bigger.

This causes the so-called Manhattan phenomenon in which the surface-mounted component 1 rises as shown in FIG.

The smaller the component, the greater the surface tension of the solder relative to the component's own weight, making the Manhattan phenomenon more likely to occur.

In today's electronic components, there is a tendency to make the components themselves smaller in order to improve the packaging density, and therefore the Manhattan phenomenon is likely to occur.

In addition, the recently developed vapor phase soldering method (VPS method)
, the Manhattan phenomenon is particularly likely to occur and has become a major problem.

Bonding failure due to the Manhattan phenomenon is a factor that significantly reduces the yield and reliability of reflow soldering.

In order to prevent the Manhattan phenomenon and eliminate soldering defects, it is conceivable to use an adhesive 14 to prevent the surface mount component 1 from rising as shown in FIG.

However, if this adhesive 14 is used, as shown in FIG. 7, when the surface mount component 1 is misplaced, it will be soldered in a misaligned state.

This may cause accidents such as contact with other electronic parts, so it is difficult to say that this is a reasonable solution.

If adhesive is not used, even if the component is mounted with a misalignment, a horizontal moment (arrow) due to the molten solder will act on the surface mount component 1, as shown in FIG. 8A. A direction correction force (self-alignment) acts on the surface mount component 1.

As a result, it is fixed at the normal position as shown in FIG.

When the adhesive 14 is used, the self-alignment effect of the molten solder can be utilized.

Therefore, the present invention proposes a method of manufacturing a board and a board device using non-eutectic solder, which prevents the rise phenomenon of surface-mounted components from occurring.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention uses a non-eutectic solder whose component ratio is selected so that the solidus line and the liquidus line do not coincide. At the same time, the printed circuit board to which the surface-mounted electronic component is temporarily attached by the non-eutectic solder is heated to the first heating temperature in an atmosphere at a temperature of 11.
12, the non-eutectic solder is brought into a semi-molten state, the surface-mounted electronic component is lightly bonded, and then the printed circuit board is heated to a predetermined second heating temperature that is higher than the first heating temperature. The non-eutectic solder is completely melted by being transported into a temperature atmosphere, thereby fixing the surface-mounted electronic component onto the printed circuit board. It is.

[Function] As is clear from the melting point diagram or phase diagram of the alloy shown in Figure 3, if the composition ratio of the alloy is selected so as to deviate from the eutectic point p, the solidus line Ln and liquidus line Lb of the alloy will no longer match.

For example, when using a solder with a composition ratio of Q, that is, a non-eutectic solder (binary alloy in this example), the temperature T1 of the solidus line La and the temperature 'r゛ of the liquidus line Lb are used. 2 is different.

When using this non-eutectic solder, in the first heating step, the heating temperature is passed through an atmosphere of an appropriate 7 grade Tc between T1 and T2. By passing through this temperature atmosphere, the non-eutectic solder becomes a mixture of liquid and solid. In other words, it becomes a semi-molten state.

At this time, even if the heating temperature on one electrode side is 1'e or less and the alloy solder coated on the electrode is not in a semi-molten state, the Manhattan phenomenon does not occur.

This is because the surface tension caused by the molten solder is small in the semi-molten state, and this surface tension does not apply enough force to pull up the other electrode side. As time passes, this electrode side also becomes semi-molten.

Next, proceeding to the second heating step, the temperature T at which the liquid phase state is reached is
Pass through an atmosphere heated to a temperature of 2 or more. This will completely melt the non-eutectic solder.

Here, even if only one non-eutectic solder completely melts first, the Manhattan phenomenon does not occur depending on the surface tension at that time. This is because at this point, at least the other electrode side is already in a semi-molten state. As time passes, the solder in the semi-molten state also completely melts.

Therefore, a substrate device with high yield can be provided.

Furthermore, by melting and solidifying the non-eutectic solder through two heating steps as described above, the incidence of Manhattan phenomenon can be reduced to almost zero.

[Example] Next, an example of a method for manufacturing a board device using non-eutectic solder according to the present invention will be described in detail with reference to FIG. 1 and subsequent figures.

In this invention as well, as shown in FIG.
A substrate device is formed by fixing the substrate.

For fixing the non-eutectic solder 10 and 11, a soldering device using a vapor phase solder bath in which the heating temperature can be easily adjusted is used, as will be described later.

As the solder for joining the surface-mounted component 1, a non-eutectic solder whose component ratio is selected so that the solidus line and the liquidus line do not coincide is used.

The non-bare solder will be explained with reference to the phase diagram of the alloy shown in FIG. 3 with one exception of melting point rM.

FIG. 3 is a phase diagram of an alloy solder made of a binary alloy of tin Sn and QnPb, where f) indicates the eutectic point.

The eutectic point p is the gold hL where the solidus line La and the liquidus line Lb coincide.
; Refers to the composition ratio. An alloy solder having a total bending composition of 1 at the eutectic point f is usually referred to as eutectic solder. This eutectic solder melts when a predetermined addition y, A iuu a T 1 or more is reached.

On the other hand, if a non-eutectic solder in which the composition ratio of the alloy is selected so as to deviate from the eutectic point p is used, the solidus line La and liquidus line Lb of the alloy will not match.

For example, when an alloy is constructed so that the composition ratio is Q, the temperature T1 of both phase lines Lll and the temperature T2 of the liquidus line Lb are
There is a difference between

Therefore, if the heating temperature is set at an appropriate temperature Tc between T1 and 1゛2 in the first heating step, the non-eutectic solder will be in a state where liquid and solid are mixed, that is, a semi-molten state. .

In this semi-molten state, the surface mount components are lightly bonded.

At this time, if the heating temperature on one electrode side is below Tc,
Even when the non-eutectic solder 10 completely applied to this electrode is not in a semi-molten state, a Manhattan phenomenon does not occur.

This is because the surface tension due to the solder 10 is small in the semi-molten state, and this surface tension does not apply enough force to pull up the other electrode side.

Next, in a second heating step, the heating temperature is heated to a grade of 1000 ml or more, which results in an IIR phase state. In this way,
The non-eutectic solder 10 is completely melted. Due to this additional 2Δ temperature, the non-eutectic solder 10 (11) on the other electrode side, which was in an incompletely melted state, is also completely melted.

Here, even if only one non-eutectic solder 10 completely melts first, the Manhattan phenomenon does not occur depending on the surface tension at that time. This is because at this point, the other electrode is already in a semi-molten state and is lightly metal bonded.

In addition to the above-mentioned tin and lead, the composition of the non-eutectic solder may be a quaternary alloy of 1, tin Sn, button Pb, bismuth 13i, and silver Δg in a non-eutectic state. When this non-eutectic solder is used, the solidus temperature T1 is about 189°C, and the liquidus temperature T2 is about 209°C.

Using paste-like non-eutectic solder 10 (11), the first
When the surface mount component 1 is soldered as shown in the figure, the surface mount component 1 is fixed to the printed circuit board 5 through the following steps.

The non-eutectic solder used is a solder made of a quaternary alloy (Sn--Pb--Bi-.DELTA.g) whose biphasic line and liquidus line are selected as described above. As a soldering device, a vapor phase type soldering bath which can be easily controlled by 2 degrees was used.

FIG. 2 is a process diagram for explaining an example of a method for manufacturing a substrate device according to the present invention.

First, a predetermined conductive layer 6 completely formed on the printed circuit board S,
A predetermined amount of the non-eutectic solder 10.11 described above is applied on the surface of the predetermined surface mount component 1 placed on the upper surface of the non-eutectic solder 10.11.
is temporarily fixed by this non-eutectic solder 10.11 (
Figure 2A).

In this state, the printed circuit board 5 is transported into a vapor phase soldering bath where the first heating temperature is not controlled.

The first heating temperature is a suitable temperature T which is less than or equal to temperature T1 and less than or equal to 2.
It is c. When using the above-mentioned non-eutectic solder 10.11, a solvent having a boiling point of about 190'C may be used as the solvent filled in the vapor phase solder tank.

Due to this heating condition, the solder 10.11 begins to melt.

In this case, if there is a temperature difference between the electrode parts of the surface mount component 1,
Among them, the high temperature side melts first. FIG. 2B shows the solder 10 in a semi-molten state. Therefore, 7ri
The pole portion 3 side is lightly joined with semi-molten solder 10.

On the other hand, the solder 11 on the electrode portion 4 side is not yet in a semi-molten state. However, as described above, since the surface tension due to the semi-melting of the solder 10 is extremely small, this force is not enough to lift one side of the surface-mounted component 1. Therefore, the Manhattan phenomenon does not occur.

However, since it takes some time for the solder 41 to pass through the solder 41, the solder 11 on the other electrode 16π part 4 also becomes half-melted during this passing time, and both the electrode parts 3 and 4 are non-eutectic. Lightly joined with solder 10.11 (Figure 2C)
.

Next, proceed to the second heating step. In the second heating step, the ambient temperature is selected to be equal to or higher than the liquidus temperature T2. In the example, since a solvent with a boiling point of 215°C is used, the second heating temperature is 215°C.

The above-mentioned printed circuit board 5 is transported through the vapor phase soldering bath in this temperature atmosphere. Then, the semi-molten solder 11 also becomes molten, and the electrode portion 3 is completely fixed by the non-eutectic solder 10 (FIG. 3D).

At this time, if there is a temperature difference between the electrode parts 3 and 4, the solder 11 on the electrode part 4 side will not immediately become molten for the same reason as described above. However, since the electrode portion 4 is lightly metal-bonded to the conductive layer 7 by the first heating step, the Manhattan phenomenon does not occur in this case as well.

When 1l12 is fed to the center of the solder tank, the solder 11 also melts due to the passage of time and becomes Ti41i part 4.
are also completely fixed by the non-eutectic solder 11 (E in the same figure).

In this way, while using non-eutectic solder 10.11,
By sending the particles through atmospheres with different temperatures, it is possible to almost completely eliminate the occurrence of the Manhattan phenomenon.

In addition, in the above, a vapor phase type soldering bath was used as a soldering device to obtain different heating temperatures, but this is not limited to this, and a combination of an infrared reflow oven may also be used. You may also use it. Furthermore, fA
Various types of glue flow handi such as wind type, pot plate type, etc.
It can be used in conjunction with a scouring device.

If a non-eutectic solder is formed using a binary alloy or a multi-component alloy, the composition ratio is not particularly important because the composition should be set outside the eutectic point p, but in reality -L is the same as the in-phase line. It will run better if the liquidus line is not too close.

[Effects of the Invention] As explained above, in this invention, a non-eutectic solder is used and a printed circuit board on which four surface-mounted components are mounted is transported through different temperature atmospheres. A surface mount F415 product is fixed to a printed circuit board.

According to this method, since the surface mount components are lightly metal-bonded using the solder in a semi-molten state in the first heating step, it has the practical benefit of reliably eliminating the Manhattan effect of the surface mount components.

Therefore, the present invention is extremely suitable for application to a method of manufacturing a board device on which microscopic surface mount components that have been made into chips are mounted.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of essential parts showing an example of a board device using non-eutectic solder according to the present invention, FIG. 2 is a diagram showing the manufacturing process of the board device δ according to the present invention, and FIG. Fig. 4 is a state diagram showing the state of mounting on a printed circuit board, Fig. 5 is a state diagram showing the mounting state on a printed circuit board.
The figure is a diagram showing the occurrence of the Manhattan phenomenon due to paste solder, Figure 6 is a diagram showing another conventional mounting state, Figure 7 is a plan view at that time, and Figure 8 is an explanatory diagram of the self-alignment effect. . 1...Surface mount component 3.4...7ri pole part 10.11...Non-eutectic solder

Claims (1)

[Claims] (1) A non-eutectic solder whose component ratio is selected so that the solidus line and liquidus line do not match is used, and surface-mounted electronic components are temporarily fixed with this non-eutectic solder. The printed circuit board is transported into a temperature atmosphere at a first heating temperature, the non-eutectic solder is brought into a semi-molten state, the surface mount type electronic component is lightly bonded, and then the printed circuit board is heated. The surface-mounted electronic component is transported into a temperature atmosphere heated to a predetermined second heating temperature that is higher than the first heating temperature, and the non-eutectic solder is completely melted. A method of manufacturing a board device using non-eutectic solder, characterized in that the device is fixed on a printed circuit board.