JPS5930470A - Soldering method of wiring substrate - Google Patents

Abstract

PURPOSE:To keep parts of poor heat resistance mounted on a wiring substrate free from thermal damages by putting the wiring substrate joined tentatively with semiconductor elements into a furnace kept in an inert gaseous atmosphere and heating locally the soldered parts. CONSTITUTION:For example, a liquid crystal module 8 produced by sealing a liquid crystal 6 between a lower glass substrate 2 and an upper glass substrate 4, and joining tentatively plural pieces of semiconductor elements 10 for driving the liquid crystal on the substrate 2 by means of solder 12 is prepared. A furnace 16 kept in an inert gaseous atmosphere is provided above a preheating plate 14, is covered with a cover 2 consisting of IR transmittable glass, has introducing parts 24A, B and a discharging port 26 for an inert gas and is provided with an IR lamp 18 in the upper part. Thereupon, the module 8 is charged into the furnace 16, and an inert gas, for example, gaseous N2 is introduced into the furnace 16, then the lamp 18 is lighted to heat locally the part joined by the solder 12, thereby soldering the module 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved soldering method for soldering a semiconductor element to a wiring board having components having a heat-resistant temperature lower than the melting temperature of solder.

A typical method of directly soldering a semiconductor element to a wiring board is a microelement connecting method disclosed in Japanese Patent No. 519Q1313. At this point, solder for caulking is applied to the terminals placed on the pattern surface of the semiconductor element, and after applying flux to the bonding terminals of the wiring board, which are the mating parts to be bonded, In this method, the terminals of the semiconductor element and the terminals of the wiring board are aligned and faced, and the solder at the connection part is heated and melted to perform solder bonding.

Conventionally, when soldering using this method, the wiring board on which the semiconductor has been temporarily fixed is generally sent into a belt-conveyed heating furnace. Therefore, if the wiring board includes components that have a heat resistance lower than the solder melting temperature, they will suffer thermal damage.

The present invention has been made in view of the above-mentioned circumstances, and provides a soldering method for highly efficiently melting and bonding semiconductor elements with gold and solder without causing thermal damage to components with low heat resistance mounted on wiring boards. The purpose is to provide.

In order to achieve the above object, the wiring board soldering method of the present invention is characterized by placing the wiring board on which the semiconductor elements have been temporarily bonded into an inert gas atmosphere furnace, and locally heating the solder joints. do.

The basic principle of the invention is as follows. Melting the solder in an inert gas atmosphere eliminates the risk of oxidation of the flux, and if the solder melting joint is locally heated, the temperature of the part away from the joint will not rise to the solder melting temperature. There is no risk of thermal damage, and furthermore, by performing local heating, the solder can be quickly melted with less thermal energy consumption, thus improving work efficiency.

Next, one embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 shows a finished product of an example of a liquid crystal module as a wiring board to which the method of the present invention is applied and solder melted and bonded, showing a lower glass substrate 2 and an upper glass substrate 4.
A liquid crystal 6 is sealed between the lower glass substrate 2 and a plurality of semiconductor elements 10 for driving the liquid crystal are connected to the lower glass substrate 2. FIG. 2 is a side view of the above liquid crystal module, in which the lower substrate 2 and the semiconductor element 0 are bonded by a hunter 12. As shown in FIG.

FIG. 3 is a cross-sectional front view of an example of a soldering device configured to perform solder melting temperature using the method of the present invention;
The figure is a sectional side view of the same. A furnace 16 is provided on the preheating plate 14, and an infrared heating lamp 18 is provided above the furnace 16. The upper opening of the furnace 16 is covered with a cover 22, and this cover 22 constitutes the ceiling wall of the furnace. In this embodiment, the cover 22 is made of infrared transmitting glass, and a partition plate 23f is integrally fixed to the lower surface of the cover 22, so that the distance between the inner walls of the furnace is A.

8. It is divided into two rooms.

At one end of the furnace 16 is an inert gas inlet 24 communicating with the A chamber.
An inert gas inlet 24B communicating with chambers A and B is provided, and an inert gas outlet 2G is provided at the other end of the furnace 16.

The above-mentioned inert gas inlet ports 24A and 248K are capable of feeding N2 gas, and are equipped with the above-mentioned feeding gas heating means and flow fIk adjusting means (both not shown). It is a provision.

The partition plate 23 is arranged with respect to the cover 22 so that when the liquid crystal module 8 is inserted into the furnace 16, the semiconductor element 10 is located in the A room, and the liquid crystal covered with the upper glass substrate 4 is located in the B room. Fixed position ii1. is set. The infrared lamp 18 irradiates an arbitrary semiconductor element 10 with infrared rays in the direction of the reciprocating arrow XX and the direction of the arrow Y.
- It has a structure that can be moved in the Y direction.

A semiconductor device 1 is attached to a lower glass substrate 2 by the method of the present invention.
To solder 0, a liquid crystal module (unbonded product) 8 is placed in a furnace 16 as shown in the figure.

At this time, solder for bonding is applied in advance to the terminals of the semiconductor element 10, soldering flux is applied to the terminals of the lower glass substrate 2, and the semiconductor element 10 is positioned so that both terminals face each other. In this example, a flux with a high viscosity is used, and this flux is applied to the semiconductor element 1.
■1 plays the role of an adhesive for temporarily bonding 0 to the lower glass substrate 1O.

Prepare as above and preheat fJ 14'! i- Preheat the entire liquid crystal module 8 by raising the temperature.

The heat resistant temperature of the liquid crystal of the non-example liquid crystal module 8 is JO
The separation standard is 120°C. Therefore, the above preheating is set lower than the heat-resistant standard temperature [12oC, and in this example, it is preheated to 100C.

In parallel with the above preheating, from the inert gas inlet 24B to B
N2 gas heated to about 100° C. is fed into the room, and N2 gas heated to about 200° C. is fed into the entrance chamber from the inert gas inlet 24A. The introduced N2 gas flows through chamber A or chamber B, respectively, and is dissipated into the atmosphere from the inert gas outlet 26.

In the case of this example, the above operation is performed to change the state to 30
When the temperature is maintained for seconds, the furnace 16 becomes an inert atmosphere, and the temperature of the portion of the liquid crystal module 8 in the B chamber increases to approximately 100° C., while the temperature of the portion located in the entrance chamber rises to a temperature close to 200° C. In this state, the infrared lamp 18 is placed opposite the - semiconductor elements 10, and the infrared lamp 18 is energized to heat the semiconductor element 10 by infrared radiation until it reaches a predetermined temperature, and then the current is cut off.

In this embodiment, since solder having a melting temperature of 310 to 315°C is used, the above predetermined temperature is set slightly higher than 315°C. This melts the solder and performs the bonding. Since the inside of the furnace is filled with N2, which is an inert gas, the flux and solder used for soldering do not oxidize, and therefore highly reliable soldering can be performed.

Since the semiconductor element 10 is locally heated by infrared irradiation as described above, the liquid crystal spaced apart from the semiconductor element 10 is maintained at about 1001:1, and there is no risk of thermal damage. Furthermore, since the solder melting joint is preheated by flowing N2 gas at about 200° C. into the entrance chamber and the solder melting joint is locally heated, solder melting can be carried out quickly and work efficiency is high.

Moreover, since the entire liquid crystal module 8 is preheated to about 100'C, there is no risk of an excessive temperature gradient occurring due to the above-mentioned local heating, and therefore there is no risk of thermal cracking of the glass substrate.

In this embodiment, one infrared lamp 18 is provided,
Six semiconductor devices 1O are soldered by moving these in sequence, and two infrared lamps 18 are used.

It is also possible to provide three or six semiconductor elements 10 and simultaneously solder-melt and bond two, three, or six semiconductor elements 10. In this way, if a plurality of local heating means for the solder joint are used in correspondence with the number of semiconductor elements, the working efficiency can be further improved.

If an infrared lamp is used as a means for locally heating the entire Hunter melted joint as in this embodiment, it is convenient because the desired area of the semiconductor element can be locally heated in a non-contact manner.

The infrared irradiation may be started and ended by controlling the energization of the infrared lamp, or by turning on the infrared lamp at full speed and inserting and removing an infrared filter between the infrared lamp and the semiconductor element. You may do so.

As in this example, when N2' is used as an inert gas, the cost of using the inert gas as a consumable material is low, and even if the used waste is dissipated into the atmosphere, it is convenient because it does not cause problems with separate installation. .

In addition, if a partition wall is provided in the furnace to form a plurality of gas flow paths as in this example, and inert gases at multiple temperatures are allowed to flow through the furnace, it is possible to Work management is easy because multiple areas of the liquid crystal module 8) in the example can be selectively heated and also selectively cooled.

Furthermore, as mentioned above, when using an infrared lamp as a local heating device, if a part of the furnace wall is made of glass that transmits infrared rays, and infrared rays are irradiated from outside the furnace through this glass,
It is easy to keep the furnace airtight, and in addition, the operation and maintenance of the infrared lamp is easy.

In this embodiment, by flowing N2 gas at 200°C into the eight chambers of the furnace 160, one K produces the preheating effect of heating the semiconductor element 10 by the infrared lamp 18, as described above, and increases the solder melting temperature (310 to 315°C). ). Another effect is that when the heating by the infrared lamp 18 is stopped after the solder has melted, the semiconductor element lo is relatively quickly cooled down to 20°C by the N2 gas flow, so that the solder solidifies quickly. Increase work efficiency. Since the soil, semiconductor, body element 10, and parts adjacent thereto are kept at high temperatures for a short time, deterioration of these members due to heat can be prevented.

As an application example of the present invention, it is also possible to fully circulate an inert gas having a temperature of γb slightly higher than the solder melting temperature in the A chamber, and locally heat the solder joint by heat conduction by the gas, thereby performing -C solder melt joining. .

It is also possible to carry out the soldering method (1 method) of the present invention by providing means for locally heating the semiconductor element on the bottom side of the furnace J6. This makes it easy to open and close the furnace cover (22 in the previous example), making it convenient to take the wiring board, which is the workpiece, into and out of the furnace.

As explained above, the present invention provides a soldering method for melting and bonding all semi-3n elements on a wiring board, in which the wiring board on which the semiconductor elements are temporarily bonded is placed in a furnace in an inert gas atmosphere,... By heating the solder joints locally, it is possible to perform solder melting of semiconductor elements with high efficiency without the risk of thermal damage even if components with low heat resistance are mounted on the wiring board. can.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a liquid crystal module as an example of a wiring board which is completely soldered and bonded by applying the wiring board soldering method of the present invention, and FIG. 2 is a side view of the same. FIG. 3 is a front view showing an example of a wiring board soldering apparatus configured to carry out the entire method of the present invention, and FIG. 4 is a side view of the same. 2...1 part glass substrate, 4...upper glass substrate, 6...
...Liquid crystal, 8...Liquid crystal module, 10...Semiconductor element, 12...Solder, 14...Preheating board, 16...
・Furnace, 18...Infrared lamp, 22...Cover, 23
...Partition plate, 24A, 24B...Inert gas supply [
1,26...Inert gas discharge port. Representative Patent Attorney Tadashi Akimoto Figure 1) No. 0 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In a soldering method for melt-bonding a semiconductor element onto a wiring board, the wiring board on which the semiconductor element has been temporarily bonded is placed in an inert gas atmosphere furnace, and the soldering part is melt-bonded. 2. The wiring board according to claim 1, wherein the local heating is performed using an infrared lamp. 3. The method for soldering a wiring board according to claim 1, wherein the inert gas is N2 gas. 4. The inert gas is N2 gas. Claim 1, characterized in that a partition wall is provided in the gas atmosphere furnace to form a plurality of gas passages, and inert gases having at least two different temperatures are allowed to flow through the plurality of gas passages. The method for bonding a wiring board according to item 1. 5. Glass that transmits infrared rays is used for at least a part of the furnace wall of the inert gas atmosphere furnace, and bonding is performed from outside the furnace through this glass. 6. The method for soldering a wiring board according to claim 2, wherein the solder joint is locally heated by irradiating the solder joint with infrared light. The wiring board according to claim 1, wherein the local heating is performed using a number of local heating means corresponding to the number of 4" conductor elements to be joined by a hunter. Soldering method.