JP4129666B2 - Manufacturing method of substrate for semiconductor package - Google Patents

Description

[0001]
The present invention relates to PGA (pin grid array), BGA (ball grid array), CSP (chip size package), MCM (multi-chip module) used in electronic equipment, electrical equipment, computers, communication equipment, and the like. ), A printed circuit board used for FC-BGA (flip chip ball grid array) and the like.
[0002]
[Prior art]
Along with the high integration of semiconductor elements, it is also necessary to increase the density of printed circuit boards for semiconductor packages. In particular, in printed wiring boards used in this field, not only multilayering and thinning of wiring but also miniaturization and high density of through-holes are rapidly progressing. That is, the formation of a through hole by a laser is attempted from the formation of a through hole by a conventionally used drill. The through hole is filled with an insulating resin or the like in order to prevent deterioration of the substrate performance due to intrusion of moisture or the like.
[0003]
[Problems to be solved by the invention]
The filling of the through hole is performed at the time of solder resist coating or before solder resist coating in a separate process. However, there arises a problem that the resin filled in the hole collapses or falls off. Further, even after the semiconductor package is formed, since the hole-filling resin transmits moisture, it causes peeling between the substrate and the mold resin, so-called popcorn phenomenon. As a countermeasure against this, in a method of forming a through hole with a laser and then closing the through portion with plating, that is, sealing (hereinafter referred to as sealing the through hole with plating), a resin hole and a copper foil hole Due to the variation in the hole diameter and the variation in the shape of the copper foil holes, it is difficult to uniformly plate and seal all the holes in the substrate of 50 to 2000.
[0004]
[Means for Solving the Problems]
In the laser hole processing on the double-sided board, after forming the non-through hole leaving only the single-sided copper foil, the through hole is formed by etching, and the hole is sealed with plating to ensure conduction, and the sealed hole This is a method for manufacturing a semiconductor package substrate in which solder ball connection terminals are formed at the positions.
The present invention is a double-sided copper-clad laminate,
(1) Form a non-through hole that leaves only one-sided copper foil by laser processing (2) Form a through-hole in one-sided copper foil by etching treatment (3) Desmear treatment (4) Seal the through-hole by plating (5) A method of manufacturing a semiconductor package substrate by forming solder connection terminals at positions of sealed holes.
This invention is a manufacturing method of the board | substrate for semiconductor packages by a double-sided copper clad laminated board being board thickness 0.04-0.4mm and each copper foil thickness 5-20 micrometers of front and back.
The present invention is a method for manufacturing a substrate for a semiconductor package, wherein the laser processing is performed using a carbon dioxide laser, and the hole diameter is 70 to 120 μm.
This invention is a manufacturing method of the board | substrate for semiconductor packages by the through-hole diameter by an etching process being 10-100 micrometers.
The present invention is a method for manufacturing a substrate for a semiconductor package, in which an etching treatment is performed using an aqueous solution containing hydrogen peroxide or persulfate.
The present invention is a method for manufacturing a substrate for a semiconductor package, in which desmear treatment is performed using potassium permanganate or potassium chromate aqueous solution.
The present invention is a method for manufacturing a substrate for a semiconductor package, wherein sealing of a through hole by plating is performed by electroless plating and / or electrolytic plating.
The present invention is a method for manufacturing a substrate for a semiconductor package by performing electrolytic plating in an electrolytic copper plating solution at a current density of 0.3 to 1.5 A / dm ² .
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a non-through hole is formed in a double-sided copper-clad laminate by laser processing, and a through hole is formed by etching. After the desmear process, the circuit on the front and back of the substrate is made conductive by plating, and at the same time, the through hole is sealed. This is a method of manufacturing a printed circuit board by forming solder connection terminals at the positions of the copper foils in the plated and sealed holes (hereinafter referred to as the positions of the sealed copper foils).
[0006]
The insulating substrate used in the present invention is an epoxy resin, a bismaleimide triazine resin (BT resin), a polyimide resin, a PPO resin, or the like, or a prepreg in which these resins are impregnated with glass fiber, glass cloth, or paper. The copper foil used in the present invention is an electrolytic copper foil having a thickness of 5 to 20 μm, preferably 9 to 15 μm. A copper foil is placed on the prepreg and press-molded to form a double-sided copper clad laminate having an insulating layer thickness of 0.04 to 0.4 mm.
[0007]
The laser processing of the present invention will be described in detail.
The shape of the hole formed in the present invention is such that the surface of the copper foil and the insulating layer are formed by a laser, and the irradiation energy and the number of pulses are set so that the copper foil on the bottom surface is a non-through hole. Control the beam diameter. The laser used in the present invention is performed using a carbon dioxide laser drilling machine having a wavelength of 9 to 11 μm. Beam diameter: 50 to 150 μm; output × number of shots: (20 to 40 mJ) × (1 to 2 shot) + (10 to 20 mJ) × (1 to 4 shot). The hole diameter of the surface copper foil is the average hole diameter: A non-through hole of 90 to 100 μm is formed. If the hole diameter variation width on the surface of the hole formed in the present invention is a minimum of 70 to 120 μm and the hole diameter of the bottom of the insulating layer is 30 to 100 μm, it is a hole having a preferable shape for carrying out the present invention. is there.
[0008]
The formation of the through hole in the copper foil by the etching process of the present invention will be described.
The chemical solution for the etching treatment of the present invention is an aqueous solution of persulfate, hydrogen peroxide-sulfuric acid or the like. A hole is made in the bottom copper foil by dipping the laser processed substrate in the chemical solution or spraying the chemical solution. Furthermore, the copper surface that has come into contact with the chemical solution by the etching process is roughened. The roughened copper surface has the effect of improving the adhesion of the plated copper in the subsequent process.
The
[0009]
The copper foil on the surface melts and evaporates by laser irradiation, and the resin of the insulating layer decomposes and evaporates and is discharged, but part of it stays inside the generated through-hole, while the copper foil at the bottom of the hole The hole has not been opened by the heat, but it has been altered by heat, so in the etching process, it reacts with the remaining copper and the altered copper foil without being discharged, dissolves, and opens the pores in the copper foil at the bottom of the hole There is. However, in the etching process of the present invention, if the diameter of the hole bottom is smaller than 30 μm, it sometimes happens that the through hole cannot be formed in the etching process. Even if the hole is formed, it is difficult to continuously supply the plating component to the through-hole portion even if the plating solution is stirred or vibrated in the plating process, particularly in the electroless plating process. For this reason, sealing by plating may not be possible. Even if sealing can be achieved by plating, the thickness of the plating layer that connects the circuit patterns on the front and back of the substrate becomes too small, which may cause problems in connection reliability of plating. On the other hand, if the thickness is larger than 100 μm, in normal plating processing, the copper foil through-holes cannot be sealed or the plating becomes too thick, resulting in a decrease in pattern accuracy. There is also. On the other hand, if the diameter of the upper part of the through hole is larger than 200 μm, the hole diameter is too large, which results in inhibiting high density.
[0010]
In the desmear treatment of the present invention, the chemical solution is an aqueous solution such as permanganate or chromate, and the treatment is performed at 50 to 90 ° C. for 1 to 15 minutes. By using a method of spraying or immersing the chemical solution on the etched substrate, the dirt on the surface or the accumulated matter inside the through-hole is decomposed, dissolved and removed.
In the laser processing, the resin decomposition product of the insulating layer is not discharged from the holes, but remains inside, or the discharged decomposition product adheres to the copper foil on the surface, so it remains particularly on the bottom copper foil. Resin and resin decomposition products are factors that hinder the deposition and adhesion of plating, and cause a decrease in the adhesion reliability of plating. Therefore, desmear treatment is necessary.
[0011]
A method for sealing a through hole and conducting the front and back of the substrate by plating according to the present invention will be described.
The plating process of the present invention is performed by a combination of electroless plating and / or electrolytic plating. For example, electroless plating, electroless plating and electrolytic plating or direct plating is performed. Gold, copper, nickel, palladium, etc. can be considered as the metal used for plating, but considering the ease of plating, the performance of the board, the ease of operation in the subsequent process, and the cost, copper plating is preferable.
First, electroless plating is performed to deposit copper on the inner wall insulating layer portion of the through hole to ensure conduction between the front and back copper foil surfaces. Subsequently, the copper layer is thickened by electrolytic plating, and the through hole is completely sealed with the plating metal.
A plating metal layer is uniformly formed on the inner wall surface of the through hole by an operation such as sufficiently stirring the solution during plating, and at the same time, connected to the front and back and / or the inner layer circuit. The plating thickness varies somewhat depending on the location, but is 5 to 20 μm in the hole.
[0012]
For electroless plating, an EDTA bath or a Rochelle salt bath is used.
Subsequently, electrolytic plating is performed to increase the thickness of the plated metal to ensure conduction reliability. Electrolytic plating ensures complete sealing of the through-holes and complete conduction of the substrate. For example, the electrolytic plating solution is an electrolytic solution containing copper sulfate or copper pyrophosphate. Immerse it in the solution and pass an electric current through the substrate to deposit plated copper. Current density at the electrolytic copper plating solution is 0.3~1.5A / dm ^2. Since the copper surface is roughened by the etching process, and there is no foreign matter inside the hole by the desmear process, the adhesion of the plated copper can be made extremely high.
[0013]
At this time, the conditions of the plating process are somewhat different depending on the target substrate, but can be achieved by a commonly used method. In the case of electrolytic plating, if the current density is increased too much, the uniformity may deteriorate (increase in plating thickness variation), or plating burn may occur, and a precise pattern may not be obtained when forming a circuit in a subsequent process. is there. Moreover, when the current density is low, productivity is lowered, which is not preferable.
[0014]
A method for forming a solder connection terminal at the position of the sealed bottom copper foil of the present invention will be described. A solder connection terminal having a diameter of 0.1 to 1.0 mm is formed at the position of the sealed hole. Since the copper foils on the front and back sides of the sealed through-hole are connected by plated copper, there is no problem that the surface peels or deforms even when heating such as mounting of solder balls is performed.
[0015]
After the circuit pattern is formed, the through hole is usually covered and / or filled with an insulating material. In the present invention, a solder resist is buried in the hole and applied as a protective film for the pattern.
[0016]
The printed wiring board thus formed is used as a semiconductor package substrate on which a semiconductor is mounted.
[0017]
【Example】
The present invention was carried out according to a known method (for example, edited by CF Combs, Yoshio Adachi, Yoshito Shimada "Printed Circuit Handbook", Modern Science Co., Ltd.). For ease of understanding, description will be made with reference to the drawings.
As the insulating base material 1 used in the present invention, a BT (bismaleimide triazine resin) double-sided copper clad laminate with a glass cloth having a thickness of 0.2 mm having a copper foil 2 of 12 μm on both sides was used. With reference to the method of JP-A-61-99596, the substrate surface is blackened, and a single-sided copper foil on the bottom surface is obtained by a laser drilling machine (wavelength: 9.3 μm carbon dioxide laser; output 70 W; number of pulses 5). The non-through hole 3 is formed with only the remaining. The cross-sectional shape of the non-through hole was a tapered shape, the diameter of the bottom surface portion was 35 μm, and the diameter of the surface portion was 100 μm [Drawing 2].
The laminated plate after laser drilling is sprayed with a 12% hydrogen peroxide-6% sulfuric acid solution (30 ° C.) on the substrate surface at a spray pressure of 2 kg / m ² , and the through hole 4 is formed on the bottom copper foil of the non-through hole. I confirmed it was bright.
Subsequently, it was immersed in a 2% potassium permanganate-20% potassium hydroxide aqueous solution to decompose, dissolve and remove organic substances in the through holes [Drawing 3].
Next, plated copper 5 was deposited by electroless plating [Drawing 4] (A), and plated copper 6 was deposited by electrolytic plating [Drawing 4] (B). Electroless plating is performed in a Rochelle salt bath, and copper of thickness 0.5 to 0.8 μM is deposited on the inner wall of the insulating layer of the through hole and the surface of the upper and lower copper layers to conduct the upper and lower copper layers. It was. Subsequently, the substrate is put in an electrolytic plating solution, and the through hole is plated at a current density of 1 A / dm ² to increase the copper thickness. At the same time, the through hole at the bottom of the hole is sealed with plated copper. The copper layers on the front and back sides were connected. The plating thickness was slightly different depending on the location, but was 10 to 12 μm at the inner wall of the hole. When observing the cross section of the hole, the copper plated through hole is completely plated and sealed, and the structure of the sealed through hole is that the bottom copper layer is completely sealed with plated copper (10 to 12 μm). It was found that there was no problem in connection reliability. The plating thicknesses of the electroless plating 5 and the electrolytic plating 6 on the copper foil 2 were uniformly 15 to 20 μm. Subsequently, a circuit pattern was formed on the copper foil surface . A semiconductor package substrate having a solder connection terminal 8 at the position of the plated hole 7 was prepared by applying a solder resist, filling a hole, and forming a solder resist pattern [Drawing 5].
The occurrence of cracks in the copper foil was examined by a temperature cycle test (500 cycles at −65 ° C., 30 minutes and 150 ° C., 30 minutes), but no cracks were observed.
[0018]
【The invention's effect】
Conductivity between the front and back patterns can be ensured by a continuous plating layer, connection reliability can be improved, and high density can be accommodated.
[Brief description of the drawings]
[FIG. 1] Double-sided board [FIG. 2] Substrate with non-through holes by laser treatment [FIG. 3] Substrate with through-holes by etching treatment [FIG. 4] (A) Electroless with upper and lower copper foils conductive by electroless plating Plated copper substrate (B) Formation of plating sealing hole with plated copper by electrolytic plating, and plated copper substrate thickened by electrolytic plating
[Fig.5] Printed wiring board with solder resist pattern [Description of symbols]
1 Insulating layer 2 Copper foil 3 Non-through hole 4 Through hole 5 Electroless plated copper 6 Electroplated copper 7 Plated and sealed hole 8 Solder connection terminal

Claims (7)

In double-sided copper-clad laminates,
(1) Form a non-through hole that leaves only one-sided copper foil by laser processing (2) Form a through hole in the copper foil at the bottom of the non-through hole by etching (3) Perform desmear treatment (4) None to ensure continuity of the copper foil surface of the front and back by performing electrolytic plating, followed by thickening the copper layer by electrolytic plating to seal the through hole by plating metal (5) solder connection terminal to the position of the sealed hole For manufacturing a semiconductor package substrate characterized by comprising:   2. The method for manufacturing a substrate for a semiconductor package according to claim 1, wherein the double-sided copper-clad laminate has an insulating layer thickness of 0.04 to 0.4 mm and a thickness of each of the front and back copper foils of 5 to 20 [mu] m.   2. The method of manufacturing a substrate for a semiconductor package according to claim 1, wherein the laser processing is performed by a carbon dioxide laser, and the hole diameter is 70 to 120 [mu] m.   2. The method of manufacturing a substrate for a semiconductor package according to claim 1, wherein the through-hole diameter in the single-sided copper foil formed by the etching process is 10 to 100 [mu] m. 5. The method of manufacturing a substrate for a semiconductor package according to claim 4, wherein the etching treatment is performed with an aqueous solution containing hydrogen peroxide or persulfate. 2. The method of manufacturing a substrate for a semiconductor package according to claim 1, wherein the desmear treatment is performed with an aqueous potassium permanganate or potassium chromate solution. ^{2. The} method for manufacturing a substrate for a semiconductor package according to claim 1 , wherein the electrolytic plating is performed in an electrolytic copper plating solution at a current density of 0.3 to 1.5 A / dm2.

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