JPH0385751A - Semiconductor device and its mounting method - Google Patents

Abstract

PURPOSE:To prevent the deformation of a lead at the stage of handling and to mount a semiconductor device on a board by soldering with enough junction strength without recourse to a method of supplying solder from outside by covering the lead with a solder bridge layer which covers adjacent plural leads continuously. CONSTITUTION:The lead 6 of the body part 5 of a multipin package IC such as a QFP, etc., is put between a lower frame 2 and an upper frame 3 and is fixed with screws, and then this jig 1 is immersed in a solder plating bath A, and it is so arranged that a great part of the lead 6 is immersed in the solder plating bath A, and electric plating is done with the jig 1 as a cathode and with a solder ingot electrode 7 as an anode. In this electric plating, plated layers are deposited in order around the lead 6, but by performing electric plating until the ones adjoining each other of each plated layer deposited junction and unite with each other, a bridge layer 8 is formed.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to quad flat packages (QFP),
Regarding semiconductor devices such as multi-bin ICs such as small outline packages (SOPs) and methods for mounting these semiconductor devices on substrates, we have taken measures such as reinforcing leads, simplifying work in the mounting process, and improving the bonding strength of semiconductor devices. It is something that

"Prior Art" Conventionally, the leads of surface mount type IC packages such as QFP have tended to become thinner as the degree of integration of the IC improves. As the degree of integration increases further according to the Zabumicron rule, the leads themselves become extremely thin and their strength decreases. Or, the leads have become so weak that they are easily deformed by contact with a soldering iron during soldering.

``Problem to be Solved by the Invention'' Therefore, when mounting such an IC package on a mounting board, the conventional manual joining method using a soldering iron is not applicable at all. In other words, there is a high risk that the leads will be deformed due to the supply of solder thread or contact with a soldering iron, which not only does not improve yield and work efficiency, but also makes it difficult to obtain uniform mounting peel strength of each lead to the board. There is a problem that cannot be done.

In addition, in ICs with many pins and narrow lead (pin) spacing such as QFP, the lead spacing may be 0.65 mm or less, so if the amount of solder supplied during bonding is even slightly excessive, reflow (melting) may occur. Later, there is a risk that blister may occur due to the solder between the leads, causing short circuits between adjacent leads, and if even a small amount of solder is insufficient, the bonding strength will be insufficient, so make sure to use an appropriate amount of solder. It was extremely difficult to supply.

This invention was made to solve the above problems,
In addition to preventing deformation of the leads during transportation and handling, the semiconductor device can be soldered to the board with sufficient bonding strength and mounted without using the conventional external solder supply method, simplifying the mounting process. The purpose of this research is to present semiconductor devices that can be used as standard devices and their mounting methods.

"Means for solving the problem" In order to solve the problem, the invention stated in claim I,
In a semiconductor device that is equipped with a plurality of leads and is mounted by soldering the leads to a conductor of a substrate, the leads are covered with a semi-IJ-] bridge layer that continuously covers a plurality of adjacent leads. be.

In order to solve the above problem, the invention described in claim 2 has the following features:
In a semiconductor device that includes a plurality of leads and is mounted by soldering the terminal part of the lead to the conductor of the board, the terminal part of the lead is in contact with the conductor surface of the board. A bent portion is formed to form a solder reservoir gap, and a plurality of adjacent leads are covered with a solid layer of solder that continuously covers the leads.

In order to solve the above problem, the invention described in claim 3 has the following features:
When mounting the semiconductor device according to the first aspect, the thick film solder plating attached to the leads is melted and the leads are bonded to the conductor of the substrate.

``Function'' Adjacent leads are connected and covered with a bridge layer of solder, so the bridge layer reinforces the leads and prevents deformation of the leads.

In addition, since a bridge layer of solder is formed around the leads, during mounting, by heating and melting this bridge layer while the leads are in contact with the conductor of the board, the melted solder in the bridge layer is transferred to the leads. The contact portion between the tip and the conductor is covered, thereby joining the lead and the conductor. Therefore, there is no need to newly supply solder from the outside at the time of mounting, and the leads and the conductor of the board are bonded with sufficient strength by the molten solder.

This invention will be explained in more detail below.

1 and 2 are for explaining an embodiment of the invention as claimed in claim 1, and a semiconductor device 11 of this embodiment has a large number of chips on the outer periphery of a main body 5 of a multi-pin package IC. The leads (terminal pins) 6 are extended. These leads 6 are connected to the circuits and elements inside the main body 5, and the leads 6 extend diagonally downward from the side of the main body 5, and their tips 6a are bent. , the main body portion 5 of the multi-pin package IC is connected to the conductor II of the substrate 9 via these glues 6 .

In the semiconductor device H of this example, the leads 6 are covered with thick film solder plating. In the present invention, thick film solder plating refers to a solder plating having a sufficiently thick thickness (thickness T shown in FIG. 2) of 15 μm or more. Therefore, the lead 6 of the semiconductor device 1-1 in this example is covered with a bridge layer 8 made of thick film solder plating with a thickness of 15 μm or more. Note that depending on the type of semiconductor device H, this bridge layer 8
Although the preferred range of the thickness varies, the thickness is determined experimentally in the range of I5 to several hundred μm, and it is sufficient that the bonding strength is greater than the lower limit of the allowable bonding strength.

To form the bridge layer 8 by applying thick film solder plating to the leads 6, for example, a normal electric solder plating method is used.

FIG. 3 does not show a jig 1 for applying electrical solder plating to a large number of adhesives 6 of a multi-bin package IC such as a QFP. This jig I is composed of a rectangular upper frame 3 made of metal such as brass, a lower frame 2 made of a non-conductive material, and screws 4.

Then, as shown in Fig. 4, the leads 6 of the main body 5 of a multi-pin package IC such as QFP are sandwiched between the lower frame 2 and the upper frame 3, and are fixed with screws 4. The jig 1 is immersed in the solder plating bath A, and the leads 6 are arranged so that most of them are immersed in the solder plating bath A, and the jig 1 is used as a cathode and the solder ingot electrode 7 is an anode. It is done by plating. Naturally, a degreasing and cleaning process is carried out as part of the final treatment for the wood.

In this electroplating process, plating layers are sequentially deposited around the leads 6. By performing electroplating until adjacent ones of the deposited plating layers are joined and integrated, A bridge layer 8 can be formed.

The temperature of the plating bath A is 20 to 50°C, the current density is 2
~] 5 A/dm2 is preferable, but is not limited to this. The thickness of the solder plating film is controlled by controlling the plating time, plating bath temperature, bathing rate, bath agitation level, etc.

Furthermore, the alloy composition of the solder ingot 7 and the solder plating bath Δ is not particularly limited, and is the usual 60% tin and 40% lead.
% solder is used, and the alloy composition of the solder plating thickness obtained by electric solder plating is also the same as the composition of the solder ingot.

As described above, the bridge layer 8 allows the adjacent boards 6...
If the structure is to cover the lead 6... with the lead layer 8
Since the lead 6 is reinforced, the lead 6 will not be deformed even if a load is applied to the lead 6 during transportation or packaging.

Next, a method for mounting a semiconductor device having the bridge layer 8 having the above structure will be described.

When mounting the above semiconductor device on a board, its leads 6
Soldering can be performed using only the thick film solder plating applied to ....

FIG. 1 is for schematically explaining an example of this mounting method, and the reference numeral 9 in the figure is a substrate on which the main body 5 of the IC package is mounted, and this substrate 9 is a reinforced synthetic resin plate or the like. A conductor 11 made of copper foil or the like is pasted on the base material 10, and a cover film 12 is pasted on the conductor II, to which the leads 6 are joined. In some areas, the cover film 12 is partially removed to form a pad 13.

As shown in FIG. 1, the pads 13 of the substrate 9 are not coated with solder such as solder paste, and the conductors 11 are exposed as they are.

Then, the main body part 5 is aligned and placed on the substrate 9 so that the leads 6... of the main body part 5 come into contact with the conductors Il of the pads 13 of the substrate 9, and in this state, the leads 6... The bridge layer 8 on the surface of the leads 6 is melted by a method such as blowing heated air toward the conductor 11 or by thermocompression bonding, and the leads 6 and the conductor 11 are joined with the molten solder to perform mounting.

When this bridge layer 8 is melted, the molten solder tends to gather around the leads 6 due to the surface tension of the leads 6, so the solder at the portion connecting between the leads 6 and 6 breaks off and around each lead 6. It is attracted to the side and stays around the contact portion between the tip 6a of the lead 6 and the conductor 11, and each lead 6 and each conductor 11 are joined. Therefore, in this state, each adjacent lead 6... is separated from the conductor I+.
is joined to.

According to such a mounting method, the semiconductor device H and the substrate 9 are bonded only by the solder of the bridge layer 8 applied to the leads 6 of the semiconductor device H in advance. Therefore, during mounting, if there is no need to separately supply solder to the joint portion from the outside, there is no need to print or apply solder paste to the pads of the board in advance. Therefore, the mounting process is simplified, and the semiconductor device can be mounted by soldering using an automatic machine.

Further, according to the present invention, by controlling the thickness of the bridge layer 8, it is possible to apply a necessary and sufficient amount of solder to each individual semiconductor device, so that the semiconductor devices H can be joined by soldering. You can definitely do it.

In this respect, with the conventional method of printing solder paste onto the pads of a board, it is impossible to apply an appropriate amount of solder by changing the amount of solder applied to each pad of the board, and it is impossible to apply an appropriate amount of solder to each pad of the board. cannot be given.

Furthermore, in the case of an IC with a multi-pin package such as a QFP as a semiconductor device, sufficient bonding strength can be obtained by applying solder plating to a thickness that corresponds to the lead width W and lead pitch P shown in Figure 2. , and there is no solder bridge between the leads 6 and 6, and the lead pitch is 0.5 m.
Even ICs as narrow as 0.3 mm or less can be mounted by soldering. In particular, it has been impossible to mount an IC with a lead pitch of less than 0.5 mm by soldering using conventional solder supply methods.

FIG. 5 shows a second embodiment of the invention as set forth in claim 1, in which the outer periphery of the leads 6 is coated with a bridge layer 8' made of solder that is uniform in thickness and continuous with each other. This is what happens.

Even if the structure of this example is adopted, the same effect as the previous example can be obtained.

FIG. 6 shows a first embodiment of the invention as set forth in claim 2, in which a bent portion 62 is formed on the tip end side of the glue 61 of this embodiment. At this bent portion 62, the first
The difference from the tip 6a of the lead 6 shown in the figure is the bending angle.

That is, when the main body part 5 of the IC is positioned and installed at a specified position on the substrate IC, and the tip end of the lead 6I is installed on the surface side of the conductor 11, there is no space between the bent part 62 and the conductor 11. A bent portion 62 is formed to form a solder reservoir gap.

In this example, on board 61, the above-described claim I
It is possible to obtain the same effect as the embodiment of the invention described in .

-1,1 In addition, when the structure of this example is adopted, the molten solder generated when the bridge layer 8 is heated and melted is attracted to the solder reservoir M gap by surface tension, stays there, and solidifies. do. Therefore, the bridge layer 8 existing between adjacent leads 61, 61 is sufficiently separated for each lead 61, and the tip of the lead 61 and the conductor 11 are completely joined. When the solder is drawn into the solder pool gap by surface tension in this manner, the bridge layer 8 between the leads 61, 61 can be completely separated, so that short circuits do not occur between adjacent leads 61, 61.

FIG. 7 shows a second embodiment of the invention as set forth in claim 2, and in this example, a zigzag-shaped bent portion 64 is formed on the tip end side of the lead 63.

With the structure of this example, the same effects as those of the previously described example can be obtained.

By the way, the bridge layer 8 used in each of the above embodiments
．． The means of forming 8° is not limited to the Metsuki method;
If it is a method that does not cause the lead to become deformed,
2- There is no problem in using methods other than the Metsuki method.

"Effects of the Invention" As explained above, according to the present invention, adjacent leads are connected and covered with a bridge layer of solder, the leads are reinforced by the bridge layer, and the bridge layer prevents deformation of the leads. Therefore, even if some load is applied to the reed during transportation or handling, the reed will not be deformed.

Further, when mounting on a board, bonding can be performed using only the solder of the bridge layer, which eliminates the need for newly supplied solder, which simplifies the mounting process and reduces mounting costs. Further, in the board mounting process, there is no need to consider the amount of solder and the solder supply method, so that the semiconductor device can be easily joined by positioning it on the board and melting the solder of the leads. Furthermore, since no load is applied to the leads during mounting, the leads will not be deformed. Furthermore, the bridge layer formed on the leads can be easily formed to have a uniform thickness, so unlike when printing solder on a board, it is easy to set the appropriate amount of solder for each semiconductor device. I can do it.

On the other hand, if a solder plating layer is formed that matches the size of the lead pitch and lead width, even when soldering a multi-pin type semiconductor device with a narrow pitch of 0.5 mm or less, there will be no bridging. This has the effect of making it possible to bond with high strength.

Furthermore, when the lead has a bent part at its tip, surface tension can attract solder into the solder pool gap formed between the conductor surface of the board and the adjacent conductor surface during mounting. The bridge layer existing between the - leads can be completely separated for each lead, and adjacent leads can be joined without causing a short circuit.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the semiconductor device of the invention as set forth in claim 1 installed on a substrate, FIG. 2 is a cross-sectional view showing the lead and bridge layer of the same-point embodiment, and FIG. is an exploded perspective view of a jig used for carrying out the invention set forth in claim 3; FIG. 4 is a sectional view showing a state in which thick film plating is applied to leads of a semiconductor device; and FIG. 5 is set forth in claim I. 6 is a sectional view of the first embodiment of the invention set forth in claim 2. FIG. 7 is a sectional view of the second embodiment of the invention set forth in claim 2. It is. A...Solder bath, ■4...Semiconductor device, D...Solder reservoir gap, ■...Jig, 5...Multi-pin package IC main body, 661.63...Lead (pin terminal) ), 8, 8
'... Bridge layer, 7... Solder ingot electrode, 9
...Substrate, II/Conductor, 62.64...Bending part.

Claims (3)

[Claims] (1) In a semiconductor device that includes a plurality of leads and is mounted by soldering the leads to a conductor of a substrate, the leads are covered with a solder bridge layer that continuously covers a plurality of adjacent leads. A semiconductor device characterized by: (2) In a semiconductor device that is equipped with a plurality of leads and is mounted by soldering the terminal ends of the leads to the conductors of the board, the ends of the leads are soldered between the ends of the leads and the surface of the conductor when attached to the board. A semiconductor device characterized in that a bent portion is formed to form a reservoir gap, and the lead is covered with a solder bridge layer that continuously covers a plurality of adjacent leads. (3) A method for mounting a semiconductor device, characterized in that when mounting the semiconductor device according to claim 1, a bridge layer of solder attached to the lead is melted to join the lead to a conductor of a substrate.