JPS61261471A - Partial coating method - Google Patents

Abstract

PURPOSE:To attain highly accurate and high-quality partial coating by conforming via locating means a substrate bar and a masking bar of the same length to a prescribed position and then by subjecting the substrate to partial coating. CONSTITUTION:The masking bar 14 having a length equal to that of the substrate bar 12 and also having openings of the same shape as that of a film to be formed on the substrate bar 12 is prepared. The masking bar 14 and the substrate bar 12 to be partially coated are continuously fed into a vacuum vessel to allow the two bars 12, 14 to adhere each other. Subsequently, in a locating zone B, guide holes provided to the above bars 12, 14 are pierced with the pins of a sprocket 18 to subject the bars 12, 14 to locating. Then the above substrate bar 12 is partially coated in a film-forming zone C.

Description

[Detailed Description of the Invention] 11 Yu Einggomi minutes! The present invention relates to a method for continuously partially coating a long strip in a vacuum container, and more specifically, it relates to a method for continuously partially coating a long strip in a vacuum container, and more specifically, it provides high quality and high quality coating by a simple means.
The present invention relates to a method for partially covering long strips that can form highly accurate partial coverings.

Conventional technology An example of a field where continuous partial coating is required on a long strip is lead frames used in the packaging of various electronic components such as semiconductor integrated circuit devices (ICs). It will be done. Generally, this lead frame is used with the wire bonding parts on it coated with precious metals or AI, etc., but in recent years, trends in IC have led to higher reliability, smaller size, and lower cost. Spot-shaped Al-coated lead frames are being used exclusively.

The manufacturing method of such a lead frame having a spot-like Al coating includes a cladding method in which aluminum foil is cold-pressed using a roller or the like, or a vacuum evaporation method is used to coat the entire surface of the metal tape with A1, and then A1 is coated on the entire surface of the metal tape. In order to leave only the necessary parts of the coating, methods have been adopted, such as applying an organic film to the part, or chemically etching the remaining part while holding it down with rubber etc. to obtain a spot-like Al coating.

However, with the cladding method, it is difficult to form a coating of a predetermined shape discontinuously at a predetermined interval, and the latter method, which uses vacuum evaporation, requires a large number of steps and There are problems with contamination due to contact with organic films, rubber, etc., and it is difficult to say that this method is advantageous in terms of cost and quality.

For these reasons, there has recently been a strong demand for the development of a method for directly forming spot-like A1 coatings. By the way, as for the cladding method of cold-pressure welding AI foil, it is extremely difficult to obtain a product that is satisfactory in terms of quality due to the limitations of the manufacturing method itself as described above. That is, when trying to directly form a spot-like A1 film using the cladding method, there are two main types of methods that can be considered. A first method is to cold press an AI foil 2 having an opening 1 in a predetermined portion as shown in FIG. 3. In the cladding method, positioning with the substrate is determined by applying a predetermined tension to the AI foil, but with a layered foil shaped like the one shown in Figure 3, the part 3 connecting the spot shaped parts 1 is Since it is thin, it is not possible to apply sufficient tension. Furthermore, if tension is applied to such a complicated shape, stress will be concentrated at each location, resulting in problems such as twisting of the AI foil, and therefore sufficient positioning accuracy cannot be obtained.

A second method is to temporarily attach the AI foil piece to the substrate tape and then cold press it.

However, with this method, it is necessary to temporarily fix the A1 foil piece to the board tape with an adhesive, etc., which causes contamination with the adhesive, which significantly deteriorates the quality of the lead frame, so it is not a practical method. No, no.

On the other hand, it can be said that the vacuum evaporation method is very superior in terms of quality such as positioning accuracy and Al coating purity when compared to the above-mentioned cladding method. For this reason, various methods using masking strips have been studied for direct spot formation of long strips by vacuum evaporation, but these methods require high precision positioning of the long strips and masking strips. It is important to realize this. These positioning methods include:
Broadly speaking, it can be classified into those using optical means and those using mechanical means.

In the former method, the size and positional relationship with the substrate of the spot-shaped portion are directly measured by optical means, the error from the predetermined position is calculated, and then the masking strip or the substrate strip is corrected and moved to partially cover the spot. The goal is to achieve the following. However, this method has the disadvantage that the equipment used is not only complicated but also expensive, and in some cases, evaporated matter may adhere to the optical system lens, etc., resulting in a decrease in measurement accuracy. It is hard to say that this is a preferable method.

On the other hand, in the positioning method using mechanical means, positioning is often performed by sandwiching both strips (the mask strip and the substrate strip) between two holding rollers called pinch rollers. However, in this method, when metal rollers are used, slippage is likely to occur between the strips and the rollers, making highly accurate positioning difficult. Further, even when an organic roller is used, the organic substance releases gas into the vacuum container, making it impossible to obtain a highly pure coating.

As a means to overcome these drawbacks, attempts have been made to use sprockets for the substrate strip and the masking strip to synchronize the two strips, but as a practical matter, considering manufacturing errors of the sprockets and periodic rotation errors of both sprockets, etc. , it is difficult to achieve high precision positioning. Furthermore, it is known that the sprocket pin lifts up the substrate strips and masking strips during running, and this makes it impossible to obtain highly accurate partially coated products.

Problems to be Solved by the Invention As detailed above, in light of recent trends in lead frames used in electronic components such as ICs, improvements in reliability, miniaturization, and cost reduction, Therefore, partially covered products are becoming mainstream. However, as mentioned above, all of the conventional partial coating methods have various drawbacks as mentioned above, and there is still much room for improvement.

Among the various drawbacks of the conventional methods described above, it is particularly important to improve the accuracy of positioning between the mask strip and the substrate strip in order to achieve continuous and efficient partial coverage. Conventionally, optical or mechanical methods are known as such positioning methods, but the equipment is complicated and expensive, the accuracy is reduced due to contamination by deposits or organic matter, and the coating purity is compromised. However, there are problems such as misunderstandings, and so far no method that is fully satisfactory is known.

Therefore, developing a method for partially covering semiconductor lead frames and the like with high positioning accuracy is of great significance in efficiently manufacturing high-quality partially covered products.

That is, an object of the present invention is to provide a simple method capable of solving the above-mentioned drawbacks and continuously forming a high-quality partial coating in a long strip with very good dimensional accuracy.

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above-mentioned shortcomings in the conventional continuous partial coating method for long strips, especially the problem of positioning accuracy. The present invention was completed based on the discovery that it is effective to provide an opening (hereinafter referred to as a guide hole) in the sprocket and utilize this for positioning, as well as to use a sprocket that does not have its own drive mechanism.

That is, the partial coating method of the present invention includes a substrate strip to be partially coated, and a masking strip having approximately the same length as the substrate strip and having film-shaped openings to be formed in the substrate strip at predetermined intervals. are continuously supplied into a vacuum container so that at least the two strips are in close contact with each other in the container, while a sprocket pin on a sprocket without a drive mechanism is inserted into a guide hole provided in the two strips. These positions are determined by penetrating the
The method is characterized in that the substrate strip is partially covered.

The continuous partial coating method of the present invention is characterized by the structure of the sprocket used, which can rotate only in the conveying direction of the substrate strip and masking strip, and applies a predetermined braking force in the opposite direction. The original drive mechanism is not provided. This consists of a substantially cylindrical or disk-shaped main body and a sprocket pin provided protruding from the surface of the main body. A plurality of protrusions spaced apart at intervals properly adapted to the

The pins of the sprocket are designed to fit into a number of holes provided on the side of the sprocket, for example, in a screw-in type or slot type. By fitting, it is possible to use a plurality of masking stripes with different opening dimensions and pitches without replacing them.

Furthermore, in the method of the present invention, the masking strip is preferably formed from a material with a smaller coefficient of thermal expansion than the substrate strip, taking into consideration the influence of heat during film formation. You can choose as appropriate depending on the balance,
Examples include stainless steel, Nitsukenopechrome, etc., or other metals and alloys, such as copper and steel coated with the above materials. Furthermore, the length of the masking strip is approximately the same as that of the substrate strip.

Furthermore, in the method of the present invention, an ion plating method is particularly used as a film forming method. Therefore, the DC method,
Any of the radio frequency method, cluster ion beam method, and hot cathode ray method can be used, and similar effects can be expected.

Moreover, the tension in front and rear of the substrate strip and the masking strip can be set individually with the sprocket as the center.

In the method of the present invention, the dimensions of the substrate strip and the masking strip (
There are no particular restrictions on the length and width, and they can be selected as appropriate depending on the intended use of the covering.

The method of the present invention is carried out by first aligning a substrate strip and a masking strip of equal length in a predetermined manner using positioning means, and then subjecting them to a film forming process.

As mentioned above, the positioning means (sprocket) used in the present invention does not have its own drive mechanism and is given a predetermined braking force in one direction, so it can rotate only in the direction in which the substrate strip, etc. runs. Therefore, unnecessary tension is not applied to the substrate strip and the masking strip.

That is, in the method of the present invention, the running of the substrate strip is provided by a winding means (such as a reel or a pinch roller) after coating. The tension of the substrate strip and masking strip can be set separately, so tension detectors are attached to the side strips to correct excess or deficiency in the preset tension and improve tension accuracy. It is also possible to devise ways of doing this.

The reason why the sprocket is not provided with its own drive mechanism is that
This is because when a generally used sprocket is also used to feed a substrate strip, etc., when the drill strip is detached from the sprocket pin, the pin gets caught in the guide hole, causing a phenomenon that lifts the strip. . Regarding this point, the inventors have investigated various materials, surface conditions, shapes, etc. of the strips and pins, but have confirmed that it is impossible to prevent the strips from lifting no matter what combination they use. .

It has been found that lifting this strip by the sprocket pin significantly impairs the precision of the coating operation, but this can be solved by not providing the sprocket with a drive mechanism, ie, a thread feeding mechanism, as in the present invention.

In the method of the present invention, a masking strip with approximately the same length as the substrate strip is used, but this is because when an endless mask is used, the evaporated material is deposited in the openings of a predetermined shape. , the size of the opening decreases, and
The mask may become deformed due to the effects of heat of condensation and radiant heat from evaporated matter,
Furthermore, it has the disadvantage that the tension cannot be maintained constant due to thermal expansion of the mask, making it difficult to cover parts with high precision.

In addition, the reason why we have adopted a mechanism that allows the front tension and rear tension of the substrate strip and masking strip to be set individually, centering on the sprocket, is due to the position of the guide hole of the strip and the pin as shown in Figure 2. In order to maintain this relationship, the forward tension must constantly increase, and especially for the substrate strip, the force is the sum of the frictional force on the sprocket roll surface due to the tension at the sprocket part and the frictional force with the masking strip. acts, requiring a forward tension greater than the frictional force.

On the other hand, the forward tension of the masking strip is basically the same as that of the substrate strip, but furthermore, the tension has a large effect on the gap between the substrate strip and the masking strip. That is, if the gap is large, the vapor deposition material wraps around the predetermined opening of the masking strip, significantly deteriorating the spot size accuracy. Therefore, the front tension of the masking strip needs to be determined by taking into account its material and required dimensional accuracy.

Further, the rear tension of the side strip is determined so that the straight portion of the sprocket pin can be completely inserted into the guide hole of the side strip without disturbing the above-mentioned state. From the above, the front tension and rear tension around the sprocket of the substrate strip and the masking strip usually have different values in order to maintain the positional relationship as shown in FIG. 2, for example. The present invention adopts a mechanism in which these can be set individually.

Finally, the reason why ion plating is adopted as a coating method is that in the case of vacuum evaporation, the adhesion between the substrate strip and the coating is poor, and to compensate for this, the substrate strip is generally preheated. However, this not only causes thermal expansion in the substrate strip, making it impossible to obtain high-precision partial coverage, but also causes thermal distortion of the substrate strip itself.Furthermore, gas is released due to heating, and the coating film itself is damaged. This is because good quality cannot be obtained. In addition, heating of the substrate strips causes heat to accumulate in guide rolls, sprockets, etc., which adversely affects their dimensional accuracy.If water cooling is used as a countermeasure, the equipment itself becomes complicated and expensive. turn into.

Hereinafter, the present invention will be explained in more detail with reference to the embodiments described with reference to the accompanying drawings. However, the scope of the present invention is not limited in any way by the following examples.

FIG. 1 schematically shows a partial coating apparatus useful for carrying out the method of the present invention, which includes a supply section A for substrate strips to be coated and masking strips, and a positioning section B1 for the substrate and mask. It mainly consists of a forming section C and a winding section for substrate strips and masking strips.

First, in the supply section A, the substrate strip 12 is fed out from the substrate supply reel 11, and the masking strip 14 is fed out from the masking strip supply reel 13, respectively. Before the substrate strip 12 comes into contact with the masking strip 14, it is subjected to ion bombardment treatment by blowing inert gas Ar from the gas inlet 15 and applying voltage from the DC power supply 16.

The substrate strip 12 and the masking strip 14 are then stabilized by guide rolls 17 and sent to the positioning station. Here, the substrate strips 12 and the masking strips 14 are positioned by passing guide pins of the sprocket 18 through guide holes provided therein in advance.

This positioning can be better understood by referring to FIG. 2, which shows an enlarged view of this area. That is, this sprocket 18 is arranged so that the sprocket pin 42 is brought into contact with the guide hole 41 provided in both the substrate strip 12 and the masking strip 14 at the rearmost part of the guide hole with respect to the running direction of both strips. so that the sprocket itself is rotated by the movement of both threads. however,
In the state shown in FIG. 2, only the first pin (for example, pin 42) needs to maintain the above-mentioned contact state at least with respect to the running direction of each strip, and the other pins (for example, pin 42) It suffices that it be in a state where it can be easily inserted into the guide holes of both strips.

Thus, the substrate strip 12 and the masking strip 14, which have been accurately aligned by the positioning tool B, are then taken to the film forming section C. In the present invention, this film forming section is constituted by an ion plating device.

In this example, the high frequency method is used, and its configuration mainly consists of a crucible 21 provided in a vacuum container, an electron gun 22, and a high frequency excitation coil 24 connected to a high frequency power source 23, as shown in FIG. It is something that will be done. here 25
is a gas introduction port through which a gas such as Ar is introduced.

After being coated in this manner, the substrate strip 12 and the masking strip 14 are sent out from the vacuum vessel, wound up and collected by the respective take-up reels 31 and 32 via the guide roll 17°.

Thus, it was confirmed that if a long strip of substrate is partially coated according to the method of the present invention, the positioning accuracy is good and lifting of the substrate strip and masking strip by sprocket pins can be completely prevented. Moreover, the quality of the obtained film was also satisfactory.

Effects of the Invention As is clear from the above explanation, according to the present invention, it is possible to significantly improve positioning accuracy using a simple method, and high-precision, high-quality partial coverage can be achieved. Although the application of the method of the present invention has been explained by taking a layer-coated lead frame as an example, the scope of application of this method is not limited to this, and the substrate strip may be made of metal or organic material, and may also be made of evaporated substances. It is not limited. Furthermore, the implementation of the present invention includes:
In addition to what is shown in Figure 2, the location of the sprocket,
It does not matter the method of supplying tension to the strip, the method of ion plating, or the method of control.

Further, in the present invention, the ion plating method is adopted with the aim of achieving a high-precision, high-quality partial coating, but it is of course possible to adopt a vacuum evaporation method or a sputtering method depending on the requirements.

[Brief explanation of drawings]

1 is a diagram schematically illustrating an apparatus useful for carrying out the method of the present invention; FIG. 2 is a diagram illustrating the positional relationship between sprocket pins and guide holes in the present invention; FIG. 3 is a schematic diagram showing an AI foil for direct A1 partial coating by the cladding method. (Main reference numbers) 1...Opening, 2...A1 foil 11...Substrate strip supply reel, 12...
...Substrate strip, 13...Masking strip supply - Knope 14.
......Maskink strip, 15.25...Gas inlet, 16...DC power supply, 17.17°...Guide roll, 18... ... Sprocket, 21 ... Crucible, 22 ... Electron gun, 23 ... High frequency power supply, 24 ... High frequency excitation Coil, 31...
... Board strip take-up reel, 32... Masking strip take-up reel, 41... Guide hole, 42.42'... Sprocket pin, Patent application Am View Request% νj crystal

Claims (4)

[Claims] (1) A substrate strip to be partially covered and a masking strip having approximately the same length as the substrate strip and having film-shaped openings to be formed on the substrate strip at predetermined intervals are placed in a vacuum container. , at least a sprocket pin on a sprocket that is continuously supplied so that the two threads are in close contact with each other in the container, and that has no drive mechanism in the guide holes provided in the two threads and is freely rotatable in one direction. These positions are determined by penetrating the
A method for partially covering a long substrate strip, comprising partially covering the substrate strip. (2) The movement of the two strips is performed by a take-up reel or a pinch roller of the strip, and a sprocket pin passing through a guide hole of the strip is located at the rearmost part of the opening of both strips with respect to the running direction of the strip. 2. The partial covering method according to claim 1, wherein positioning is carried out by contacting with. (3) The partial coating method according to claim 1 or 2, wherein the front tension and rear tension of the substrate strip and the masking strip are individually set around the sprocket. (4) The partial coating method according to claim 1, 2, or 3, wherein the coating method is an ion plating method, a vacuum evaporation method, or a sputtering method.