JP2688100B2 - Semiconductor mounting substrate and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor mounting substrate, and more particularly to a semiconductor mounting substrate used to provide a high-density, multi-terminal package at low cost.

(Prior art)

In recent years, with the progress of the electronic industry, the demand for electronic devices has been toward smaller size and higher speed.
Along with this trend, the number of input / output terminals of nuclear semiconductor components has increased significantly. Therefore, recently, connection of this semiconductor component to a printed wiring board has become an important issue.

Conventionally, a semiconductor component having a large number of input / output terminals and a printed wiring board are connected via a package. A typical such package is a single chip type package in which only one semiconductor component is mounted.

For example, the PGA (Pin Grid Array) type is a type in which semiconductor parts are connected by using a large number of conductor pins arranged in a predetermined array and conductor circuits formed on a substrate, and TAB (Tape Automated Bonding) ) Type is a form in which a finger lead formed as a part of a conductor circuit formed on a substrate and an electronic circuit component are connected by thermocompression bonding, and potted with a resin for sealing. The QFP (Quater Flat Package) type is a type in which a lead frame and a semiconductor component are connected by wire bonding and transfer molding is performed.

However, in the PGA package, there is a lower limit to the distance between the conductor pins, and thus there is a limit to the increase in density. Also,
The TAB type package requires a special mounting machine when thermocompression bonding the finger leads and semiconductor components,
The production cost will increase. More general said QFP
It is difficult for the type package to form a fine pattern, and there is a limit to high density.

That is, when mounting a component having a large number of output / input terminals, it is generally necessary to form a fine pattern on the lead frame. However, the lead frame needs to have some strength, and usually has a thickness of about 150 μm. Therefore, it was extremely difficult to etch this into a fine pattern.

[Problems to be Solved by the Invention]

In view of such a situation, conventionally, some techniques for improving the above QFP have been proposed. That is, as an improvement of a package in which a semiconductor component and a lead frame are connected by a substrate on which a fine conductor circuit is formed, a substrate on which a conductor circuit is formed and a lead frame are electrically connected by wire bonding. Then, the conductor circuit and the semiconductor component are connected by wire bonding, and then transfer molding is performed.The substrate on which the conductor circuit is formed and the lead frame are electrically connected through a through hole to form a conductor circuit. Proposals have been made such as those in which semiconductor components are connected by wire bonding and then transfer molding is performed.

However, the former package has problems such as lack of connection reliability because the lead frame and the circuit on the substrate are connected by wire bonding. On the other hand, in the latter package, since the lead frame and the circuit on the substrate are connected by through holes, high connection reliability can be obtained, but there is a problem that the manufacturing process is very complicated. Further, each of the packages obtained by these improvements has a drawback that the cost is high because each package is manufactured by combining the substrate and the lead frame.

An object of the present invention is to provide a semiconductor mounting substrate that constitutes a package for high-density mounting with high reliability when mounting a multi-terminal semiconductor component on a printed wiring board, and The purpose is to establish a technology that enables inexpensive supply of semiconductor mounting substrates.

[Means for Solving the Problems]

As a result of earnest research to realize the above object, the present inventors focused their attention on a lead frame provided with a die pad, formed a conductor circuit on this lead frame by an additive method, and formed this conductor circuit and the lead of the lead frame. It was found that the above problems can be solved by connecting with a plated conductor, and the present invention has been completed here.

That is, according to the present invention, an insulating material is arranged in at least one of the gap between the lead of the lead frame and the die pad, the gap between the leads and the surface of the lead frame, and the insulating material is arranged. An adhesive layer is provided on at least a part of the lead frame in the above state, a conductor circuit formed by an additive method is provided through the adhesive layer, and the conductor circuit and the lead are provided,
We propose a semiconductor mounting substrate that is connected by a plated conductor.

In manufacturing a semiconductor mounting substrate having at least a lead frame and a conductor circuit, at least the following three steps are performed: (a) a gap between the lead frame lead and die pad, and a space between the leads. Filling or forming an insulating material in at least one of the gap and the surface of the lead frame, and (b) forming an adhesive layer on at least a part of the lead frame in which the insulating material is arranged. (C) a step of forming a plated conductor circuit by the additive method via the adhesive layer and continuously forming the conductor circuit and the lead of the lead frame integrally or separately connecting via a connecting conductor We propose a method for manufacturing a semiconductor mounting substrate, which is characterized by being manufactured through the following steps.

In the present invention, the lead frame means a lead and a die pad. The die pad is a portion on which a semiconductor component is directly or indirectly mounted. The die pad functions as a heat radiator when directly mounted, and has a role as a reinforcing material when indirectly mounted.

It is preferable that the conductor circuit is integrally formed as a plated conductor when connecting to the lead.

At least one of the insulating material layer and the adhesive layer is preferably formed by screen printing.

Further, the adhesive layer is made of a heat-resistant fine powder soluble in an oxidant dispersed in a heat-resistant resin that is hardly soluble in an oxidant, and a plated conductor circuit is formed. The surface is preferably a roughened surface by roughening treatment with an oxidizing agent.

[Action]

The semiconductor mounting substrate of the present invention is filled with an insulating material in at least one or more of the gap between the lead of the lead frame and the die pad, the gap between the leads and the surface of the lead frame or the surface of the lead frame. Is formed so as to cover at least a part thereof. The reason why the insulating material is provided at a predetermined portion of the lead frame is to integrate the leads and the die pad to reinforce the substrate and to reliably insulate the leads and the leads and the die pad from each other.

As the insulating material layer, a thermosetting heat resistant resin such as a bisphenol A type epoxy resin, a phenol novolac epoxy resin, or a cresol novolac epoxy resin is suitable.

One of the features of the present invention is that an adhesive layer is formed on at least a part of the lead frame in which the insulating material is arranged, and a conductor circuit is formed by an additive method through the adhesive layer, and The point is that the conductor circuit and the lead are connected integrally by a plating method or via another connecting conductor which is also formed by plating.

The lead frame in which the above-mentioned insulating material is arranged is composed of the lead, the die pad and the insulating material. Therefore, in at least a part of the lead frame in which the insulating material is arranged, not only the part consisting of the insulating material layer, that is, the surface of the insulating material, but also the inside of the insulating material is included. It also includes a case where the inner layer circuit is formed through the through hole.

The reason for forming the conductor circuit via the adhesive layer by the additive method is firstly that such a method facilitates formation of a fine-patterned conductor circuit. Secondly, since the conductor circuit formed on the adhesive layer and the lead of the lead frame are connected by the conductor circuit formed by plating, extremely high reliability can be obtained. is there.

In the present invention, the conductor circuit formed via the adhesive and the conductor circuit formed between the adhesive layer and the lead frame are integrally formed as a plated conductor. Is desirable. This is because the process is simpler and the connection reliability is further improved.

Therefore, a mode in which a conductor circuit such as a connecting circuit that connects the conductor circuit and the lead frame is subsequently formed by a plating method and connected to a conductor circuit previously formed via an adhesive layer is also an embodiment of the present invention. It can be said that it is an aspect.

The plated conductor is a conductor layer or a conductor film formed by plating.

Such a semiconductor mounting substrate can be applied to either a single chip type or a multi-chip type, and the lead frame is a plug type (for DIP).
Or surface mount type (for FP).

In the present invention, the insulating material layer may be used instead of the adhesive material. In this case, an adhesive layer is formed in the gap between the lead of the lead frame and the die pad or the gap between the leads. However, this type is more preferable because it has a simpler structure.

Now, in the present invention, the adhesive layer used in forming a conductor circuit by the additive method is a heat-resistant fine powder soluble in an oxidizing agent, dispersed in a heat-resistant resin hardly soluble in the oxidizing agent. In the
At least the surface on which the plated conductor circuit is formed is preferably a surface roughened by a roughening treatment with an oxidizing agent.

The adhesive constituting this adhesive layer is composed of (a) heat-resistant resin particles having an average particle diameter of 2 to 10 μm and heat-resistant resin fine particles having an average particle diameter of 2 μm or less Mixture with powder, (b) pseudo particles obtained by adhering heat-resistant resin fine powder having an average particle size of 2 μm or less on the surface of heat-resistant resin particles having an average particle size of 2 to 10 μm, or (c) average particle size 2 μm It is preferable to disperse at least one kind of heat resistant particles selected from the following: agglomerated particles of the heat resistant resin fine powder obtained by aggregating to have an average particle size of 2 to 10 μm.

The reason for using such an adhesive layer is that it is convenient for uniformly roughening the surface of the adhesive layer. That is,
In the case of the adhesive used in the present invention, the heat-resistant particles and the heat-resistant resin forming the matrix have a large difference in solubility in an oxidizing agent. Only the heat resistant particles dispersed in the surface portion of the layer are preferentially dissolved and removed.
Therefore, the surface of the adhesive layer after treatment with the oxidant is
Has been uniformly roughened due to the heat-resistant particles removed,
It acts as an effective anchor for the conductor circuit that will be formed on the surface later. Therefore, the plated conductor circuit formed by the additive method has high adhesion strength and ensures reliability.

The adhesive layer also has a function of insulating the die pad of the lead frame from the plated conductor circuit. The preferable thickness of this adhesive layer is 5 to 30 μm.

As the heat-resistant particles in the adhesive, a resin having excellent heat resistance and electrical insulation and having stable properties against chemicals other than the oxidizing agent is used. When this resin is hardened, it becomes sparingly soluble in the heat-resistant resin liquid or solvent, but soluble in the oxidizing agent.

As the resin constituting such heat-resistant particles, for example, at least one selected from an epoxy resin, a polyester resin, and a bismaleimide-triazine resin
There are several species, and epoxy resin is particularly preferable.

As the oxidizing agent used in the oxidation treatment,
Chromic acid, chromate, permanganate, ozone, etc. are used.

Further, when forming a plated conductor circuit on the adhesive layer and the lead frame by the additive method, it is preferable to make the shape as small as possible. The allowable step thickness is preferably 50 μm or less. If the step is unavoidably large, it is desirable to form a taper.

The additive method adopted in the present invention is the first
On the adhesive layer to which nuclei are formed, a plating resist is formed, and then electroless plating is performed, or after the electroless plating is performed, further electrolytic plating is performed, and then a full additive that forms a conductor circuit is formed. It is the law. Second,
By applying electroless plating to the entire surface of the adhesive layer to which nuclei are applied, or after performing electroless plating and further electrolytic plating, a pattern is formed by forming an etching resist and then performing etching. The semi-additive method of forming is also applied to this invention.

In the present invention, an insulating layer may be further provided on the lead frame in addition to the adhesive layer to form an inner layer circuit, and the conductor circuit may be multilayered.

In addition, the conductor circuit is manufactured by a build-up method,
It is also possible to connect the inner layer circuits with via holes.

The metal used for the electroless plating or electrolytic plating is preferably at least one selected from gold, silver, copper, nickel and the alloys thereof. In particular, when connecting semiconductor components and conductor circuits by wire bonding using gold wires, in order to improve the connection reliability of gold wires, copper is used for the conductor circuits, the surface of which is nickel-plated, and the surface It is desirable to apply gold plating to the. Further, it is advantageous to apply gold plating to the semiconductor mounting portion.

Now, in the semiconductor mounting substrate of the present invention, after mounting the semiconductor component, it is desirable to seal the conductor circuit portion using a sealing resin by a potting method or a transfer molding method. Silicon resin, epoxy resin, or the like can be used as the sealing resin used for this purpose.

Next, a method of manufacturing the semiconductor mounting substrate of the present invention will be described.

The semiconductor mounting substrate manufacturing method of the present invention is novel in that it employs the following characteristic steps. That is, (a) an insulating material is applied to at least a part of the lead frame including the die pad, that is, in a gap between the die pad and the leads, in a gap between the leads, or at least a part of the surface of the lead frame. A step of forming by filling or coating, (b) a step of forming an adhesive layer on at least a part of the insulating material arranged in the lead frame in the step (a), (c) via the adhesive layer And a plating conductor circuit is adhered and formed by the additive method, and the conductor circuit and the lead of the lead frame are continuously integrally molded, or a separate connection conductor is formed and connected by the plating method.

The lead frame used in the production of the semiconductor mounting substrate of the present invention is a lead frame that is processed into a predetermined shape by a method such as etching or punching in advance, or a metal plate before being processed into the lead frame, or a partly processed It may be of a type that directly uses things. However, when using a metal plate before being processed into a lead frame or a partially processed one, an adhesive layer is formed on the metal plate, and a plated conductor circuit is subsequently formed by an additive method, followed by etching or the like. It is necessary to process it into a predetermined shape.

As a method of processing the lead frame into a predetermined shape, it is preferable to use a method of forming an etching resist on a metal plate and then performing an etching treatment.

In the above-described manufacturing method of the present invention, the surface of the lead frame having the adhesive layer formed thereon is subjected to blackening treatment for the adhesive layer surface, and blackening reduction treatment is performed for the lead portion. It is desirable to roughen by applying. This roughening treatment is performed to improve the adhesiveness (anchor effect) between the adhesive and the plated conductor and to improve the adhesiveness between the lead and the plated conductor.

In addition, in the manufacturing method of the present invention, the effect of the present invention is not impaired even if an adhesive is used for the portion where the insulating material layer is formed, and this embodiment is also the manufacturing method of the present invention. In this method, the insulating material layer and the adhesive layer can be formed at the same time, which has the advantage of simplifying the process.

In the present invention, a gap between each lead or a gap between the lead and the die pad or an insulating material layer on the lead frame surface,
Alternatively, as a method for forming the adhesive layer, a method by screen printing is desirable.

In the present invention, the adhesive layer used as a substitute for a part of the insulating material is formed by applying an uncured adhesive resin solution or screen-printing it, or by attaching a semi-cured adhesive resin film. Form. Then, it is advantageous to roughen the adhesive layer after preliminarily pre-treating the surface portion by means such as polishing using a fine-powder abrasive or liquid homing, and then lightly removing it.

The plating resist used in the present invention may be formed by printing a liquid resist and drying and curing it, or by exposing and developing a photosensitive dry film.

〔Example〕

 Next, the present invention will be described with reference to examples.

Example 1 (1) Based on a metal sheet manufactured by a punching method, a lead frame 3 as shown in FIG. 1 (a) was formed between a lead 3a and a die pad 3b of FIG. 1 (b). ), The sealing resin, that is, the insulating material 11 was embedded and cured.

(2) Next, 60 parts by weight of phenol novolac type epoxy resin, 40 parts by weight of bisphenol A type epoxy resin, 4 parts by weight of imidazole curing agent, and 10 parts by weight of epoxy resin powder (particle size 3.9 μm) having a large particle size, and Butyl carbitol was added to 25 parts by weight of epoxy resin powder with a small particle size (particle size 0.5 μm), the viscosity was adjusted to 250 cps with a homodispers disperser, and then kneaded with 3 rollers to obtain an adhesive solution. Prepared.

This solution is applied only to the portion where the sealing resin, that is, the insulating material 11 is filled, and dried and cured at 100 ° C. for 1 hour and 150 ° C. for 5 hours to give a solution as shown in FIG. 1 (c). The adhesive layer 4 was formed.

(3) Next, the lead frame that has undergone the treatment in the previous step is dipped in a 800 g / l chromic acid solution (70 ° C.) for 10 minutes,
After roughening the surface of the adhesive layer 4 as shown in FIG. 1 (d),
Neutralized and washed.

(4) Next, a catalyst was applied onto the adhesive layer 4 of the lead frame 3.

(5) Next, in order to form a predetermined conductor circuit, a photosensitive liquid resist was used to form a plating resist 6 as shown in FIG. 1 (e).

(6) Next, electroless copper plating is applied to the surface of the lead frame 3 that has been subjected to the treatment of the previous step (5) to form a plated conductor circuit 7 as shown in FIG. 1 (f), and then the plating resist. By peeling off 6, the semiconductor mounting substrate as shown in FIG. 1 (g) was manufactured.

Example 2 This example is basically the same as Example 1, but
By applying the adhesive solution not only on the insulating material 11 but also on a part of the lead frame, the second
A semiconductor mounting substrate as shown in FIG.

Example 3 (1) An adhesive solution was produced in the same manner as in the step (2) of Example 1.

(2) In the gap between the lead 3a and the die pad 3b of the lead frame 3 having the shape shown in FIG.
The insulating material 11 was embedded and cured to obtain a lead frame as shown in FIG. 3 (b).

(3) Apply the adhesive solution of the above step (1) on the lead frame 3 filled with the insulating material treated in the previous step (2), and dry and cure at 100 ° C. for 1 hour and 150 ° C. for 5 hours. Then, the adhesive layer 4 was formed.

(4) Next, after dipping the lead frame 3 subjected to the treatment in the step (3) in 800 g / l chromic acid solution (70 ° C.) for 10 minutes to roughen the surface of the adhesive layer 4, After neutralization and washing, a lead frame as shown in FIG. 3 (c) was obtained.

(5) Next, a catalyst was applied to a predetermined position on the adhesive layer 4 on the lead frame 3 by a conventional method.

(6) Next, in order to form a predetermined conductor circuit, a photosensitive liquid resist is applied to the surface of the lead frame 3 and the adhesive layer 4.
Was applied to a portion where the pattern (conductor circuit) was not formed to form a plating resist 6.

(7) Electroless copper plating is applied to the lead frame 3d that has undergone the process of the step (6), and only on the adhesive layer 4,
A conductor circuit was formed.

(8) Next, after the plating resist 6 on the lead frame 3 is partially peeled off, nuclei are applied only to the peeled portion 6 ', electroless copper plating is performed, and then pattern plating 7'is formed by electrolytic plating. Then, the leads and the conductor circuit were electrically connected to each other to manufacture the semiconductor mounting substrate shown in FIG.

Example 4 On the semiconductor mounting substrate 3 including the leads and the die pad obtained in Example 3, nickel plating was further applied, and then gold plating was performed to form a nickel-gold plating layer.
FIG. 4 shows that the IC chip 12 is mounted and the IC chip 12 and the alloy plated conductor circuit 10 are connected by wire bonding using the gold wire 9.

In addition, in the present invention, all of the semiconductor mounting substrates are resin-molded by transfer molding using epoxy resin in a portion where a circuit is formed, and all of these substrates are extremely reliable. Was confirmed.

〔The invention's effect〕

As described above, the semiconductor mounting substrate of the present invention can mount high-density, multi-terminal semiconductor components with high reliability. Moreover, according to the present invention, a high-precision multi-terminal package can be supplied at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a manufacturing process of a semiconductor mounting substrate of Example 1, FIG. 2 is a diagram showing a manufacturing process of a semiconductor mounting substrate of Example 2, and FIG. FIG. 4 is a diagram showing a manufacturing process of the semiconductor mounting substrate of Example 3, and FIG. 4 is a sectional view (a) and a plan view (a) of a package manufactured using the semiconductor mounting substrate obtained in Example 3. b), FIG. 5 shows a plan view of the lead frame used in the present invention. 3 ... Lead frame, 3a ... Lead, 3b ... Die pad, 4
... Adhesive layer, 5 ... Polyester film, 6 ... Plating resist, 6 '... Exfoliated part plating resist, 7, 7' ... Conductor circuit and plated conductor layer, 9 ... Gold wire, 10 ... Nickel-gold plating layer, 11 ... Insulation, 12 ... IC chip

Claims (6)

(57) [Claims] 1. An insulating material is arranged in at least one of a gap between a lead of a lead frame and a die pad, a gap between the leads and a surface of the lead frame, and the insulating material is arranged. An adhesive layer is provided on at least a part of the lead frame in the above state, a conductor circuit formed by an additive method is provided through the adhesive layer, and the conductor circuit and the lead are formed by a plated conductor. A semiconductor mounting board characterized by being connected. 2. The semiconductor mounting substrate according to claim 1, wherein the entire conductor circuit is integrally formed by a plating method. 3. The adhesive layer is a layer in which heat-resistant fine powder soluble in an oxidant is dispersed in a heat-resistant resin which is hardly soluble in the oxidant, and at least a conductor thereof. 3. The semiconductor mounting substrate according to claim 1, wherein the circuit formation surface is formed as a roughened surface by a roughening treatment with an oxidizing agent. 4. When manufacturing a semiconductor mounting substrate having a lead frame and a conductor circuit, at least the following steps: (a) a gap between the lead of the lead frame and a die pad, a gap between the leads, and A step of filling or forming an insulating material on at least one of the lead frame surfaces, (b) a step of forming an adhesive layer on at least a part of the lead frame in which the insulating material is arranged, (c) ) A step of forming a plated conductor circuit by the additive method via the adhesive layer and continuously forming the conductor circuit and the lead of the lead frame integrally or separately connecting via a connecting conductor. A method for manufacturing a semiconductor mounting substrate, which comprises manufacturing. 5. The manufacturing method according to claim 4, wherein at least one of the insulating material layer and the adhesive layer is formed by screen printing. 6. The adhesive layer is a layer in which heat-resistant fine powder soluble in an oxidant is dispersed in a heat-resistant resin which is hardly soluble in the oxidant, and at least a conductor thereof. The method for manufacturing a semiconductor mounting substrate according to claim 4, wherein the circuit formation surface is formed as a roughened surface by a roughening treatment with an oxidizing agent.