JPH0781002A - Laminates - Google Patents

Abstract

PURPOSE:To provide a base plate having low coefficient of thermal expansion and excellent connection reliability when it mounts parts on its surface by improving heat resistance of an aramid fiber unwoven fablic base laminates at its moisture absorption. CONSTITUTION:An aramid fiber unwoven fabric base laminates consists of an aramid fiber unwoven fabric obtained by adhering a web with a solvent soluble adhesive and a matrix resin. For the solvent soluble adhesive, a solvent solution of an epoxy resin is most suitable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric laminate.

[0002]

2. Description of the Related Art Recently, as electronic devices have become smaller and higher in density, the components mounted on a printed wiring board have been changed from a conventional insertion type to an imposition type. The surface mounting method is becoming mainstream. Therefore, various requirements are becoming severe for copper clad laminates used as printed wiring boards.

That is, when components such as chips are surface-mounted on a printed wiring board, the matching of thermal expansion coefficients becomes a problem from the viewpoint of connection reliability. For example, a thin surface mount type TSOP (T) has been widely used recently.
hin Small Outline Packag
The coefficient of thermal expansion of e) is about 5 × 10 ⁻⁶ / ° C. However, the coefficient of thermal expansion of a fiber-reinforced plastic substrate, such as a glass cloth-based epoxy resin copper-clad laminate, which is widely used as a printed wiring board, is about 15 to 17 × 10 ^−6.
/ ° C, which is much higher than that of mounted components.

Therefore, when such a component having a low coefficient of thermal expansion is surface-mounted on a printed wiring board having a high coefficient of thermal expansion, cracks are likely to occur in the solder at the connecting portion due to the large difference in the coefficient of thermal expansion. It is not possible to secure the connection reliability to withstand. In order to improve the connection reliability with the chip component, a substrate having a thermal expansion coefficient close to that of the mounted component, that is, a low thermal expansion coefficient is required.

As a substrate material having a low coefficient of thermal expansion, a ceramic substrate such as alumina or aluminum nitride, which is different from the above organic substrates, or a metal core substrate using a low thermal expansion metal such as Invar or 42 alloy as a core is used. Has been done. However, looking at these, since the ceramic substrate is extremely hard, it cannot be machined like drilling and cutting like the organic substrate, it cannot be a large substrate, and it is lighter because it is heavier than the organic substrate. Is disadvantageous to conversion.

[0007] There are drawbacks such that it is liable to crack due to poor toughness and handling is difficult, or the process of circuit processing and multilayering is complicated and the cost is high. Further, the metal core substrate having a low thermal expansion metal as a core has drawbacks that it is heavy and cannot cope with weight reduction, and it is necessary to provide an insulating coating in the hole of the metal core when forming the through hole. Therefore, it has been desired to develop a conventional organic substrate excellent in workability and having a low coefficient of thermal expansion.

As an organic substrate having a low thermal expansion, a substrate using a low thermal expansion base material such as quartz fiber or aramid fiber has been proposed. However, quartz fibers have not been put to practical use because they have extremely poor machinability and are expensive.

On the other hand, aramid fiber has a negative coefficient of thermal expansion, and the coefficient of thermal expansion in the plane direction of the aramid fiber nonwoven fabric substrate laminate using the same is lower as the volume content of aramid fiber is higher. When the volume content is 50% or more, the coefficient of thermal expansion becomes 1 × 10 ⁻⁵ / ° C. or less, and high connection reliability with mounted components, which cannot be obtained by a laminated plate using ordinary glass fibers, can be obtained.

As a conventional aramid fiber nonwoven fabric, a web, which is an aggregate of the fibers, is bonded by an aqueous emulsion adhesive, and a thermosoftening resin or fiber is mixed in the web and heated to melt them. It is known that the webs are joined together and the webs are joined together by these combinations.

[0010]

However, the water-based emulsion adhesive has a weak adhesive force with the aramid fiber. Therefore, when a heat resistance test such as immersing the aramid fiber non-woven fabric substrate in a solder bath after absorbing moisture, peeling occurs at the interface between the adhesive and the aramid fiber, which is a starting point and easily causes blisters. There is The one that heat-softening resin or fiber is mixed and heated to melt them,
Inferior heat resistance. That is, the greatest drawback of the aramid fiber non-woven fabric substrate laminate is that it has poor heat resistance when absorbing moisture.

The present invention is to improve the heat resistance when absorbing moisture, which is the greatest drawback of this aramid fiber non-woven fabric substrate, whereby the coefficient of thermal expansion is low, and when parts are surface-mounted, their connection is improved. It is intended to provide a substrate having excellent reliability.

[0012]

The present invention is an aramid fiber non-woven fabric base laminate comprising a matrix resin and an aramid fiber non-woven fabric obtained by adhering a web with a solvent-soluble adhesive.

As the solvent-soluble adhesive used for bonding the aramid fiber web, a solvent solution of thermosetting resin such as epoxy resin, polyimide resin, phenol resin, vinyl ester resin, silicone, melamine resin, unsaturated polyester resin is used. However, among these, the epoxy resin solvent solution is the most suitable from the viewpoint of the adhesiveness with the aramid fiber and the resistance to moisture and heat. As the solvent, a generally used organic solvent may be appropriately selected according to each resin.

For example, acetone is used for epoxy resin,
Methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether, N, N-dimethylformaldehyde,
N, N-dimethylacetamide, methanol, ethanol or the like is used alone or as a mixed solvent.

The amount of adhesion of these adhesives after drying is preferably 5 to 20 vol% with respect to the fibers. This is because if the adhesion amount is 5 vol% or less, sufficient nonwoven fabric strength cannot be obtained, and if it is 20 vol% or more, the resin impregnation property in the subsequent resin impregnation step and pressing step is impaired, and voids may occur.

The matrix resin to be impregnated into the aramid fiber nonwoven fabric is a thermosetting resin such as epoxy resin, polyimide resin, phenol resin, vinyl ester resin, silicone resin, melamine resin, unsaturated polyester resin, polysulfone, polyetherimide, Although thermoplastic resins such as polyene ether ether ketone and polyphenylene oxide can be used, among these,
Epoxy resin is most suitable in terms of adhesion to aramid fiber and other electrical properties.

The volume content of the aramid fiber in the aramid fiber nonwoven fabric substrate laminate is 40 in order to keep the thermal expansion coefficient low.
% Or more is preferable. Furthermore, if the volume content of aramid fiber is 50% or more, the coefficient of thermal expansion will be 1 × 10 ^-5 / ° C or less, and high connection reliability with mounted components that cannot be obtained with a laminated board using ordinary glass fibers. It is more preferable because the property is obtained.

[0018]

[Function] The adhesive strength between the solvent-soluble adhesive and the aramid fiber after drying and curing is stronger than that of the aqueous emulsion adhesive,
At the same time, the moisture resistance and heat resistance of the adhesive itself after curing are superior to those of the water-based emulsion adhesive. Therefore, the heat resistance of the aramid fiber nonwoven fabric substrate laminate of the present invention when absorbing moisture is superior to the heat resistance of the conventional aramid fiber nonwoven fabric substrate laminate when absorbing moisture, and is equivalent to that of the glass epoxy laminate plate.

[0019]

Example: An aramid fiber nonwoven fabric (basis weight: 82 g / m ² ) was obtained by immersing a web of aramid fiber (using Technora manufactured by Teijin Limited) in a mixed solvent of epoxy resin methyl ethyl ketone and methyl isobutyl ketone and drying and curing. It was The weight of the adhesive epoxy resin after curing was 10% of the weight of the aramid fiber. This aramid fiber nonwoven fabric was impregnated with an epoxy resin and dried to obtain a prepreg. Four prepregs were stacked and press-molded to obtain an aramid fiber nonwoven fabric substrate laminate. The thickness of this laminate was 0.4 mm, the aramid fiber volume content was 50%, and the thermal expansion coefficient in the plane direction was 6 × 10 ⁻⁶ / ° C.
After boiling this laminated plate, place it in a solder bath at 260 ° C for 3
The solder heat resistance was examined by immersing for 0 seconds. As a result, there was no abnormality even after 5 hours of boiling treatment.

Comparative Example The same aramid fiber web was dipped in an emulsion of an epoxy resin, dried and cured to obtain an aramid fiber nonwoven fabric. The weight of the epoxy resin as an adhesive after curing is 10% of the weight of the aramid fiber, and the basis weight is 82 g / m.
^{Was 2} .

A aramid fiber non-woven fabric substrate laminate was obtained in the same manner as in the following examples. The thickness of this laminate is 0.4 mm
The aramid fiber volume content was 50%, and the coefficient of thermal expansion in the plane direction was 6 × 10 ⁻⁶ / ° C. in the state without copper flakes. After the boiling treatment, this laminated plate was immersed in a solder bath at 260 ° C. for 30 seconds to examine the solder heat resistance. As a result, swelling occurred immediately when immersed in a solder bath at 260 ° C. for 1 hour of boiling treatment.

[0022]

As described above, according to the present invention, in the laminated board using the aramid nonwoven fabric as a base material, the thermal shock resistance such as solder heat resistance, which has been the biggest problem until now, especially the characteristics when absorbing moisture. Can be improved. This makes it possible to take full advantage of the low thermal expansion coefficient of aramid fibers. Therefore, the laminated plate and the manufacturing method thereof according to the present invention are very effective as a low thermal expansion substrate and a manufacturing method thereof required for further miniaturization, higher density or bare chip formation of semiconductor device packages which will be further advanced in the future. The present invention can be applied not only to a laminate of aramid non-woven fabric alone, but also to a composite laminate of both woven fabric and non-woven fabric.

Claims (2)

[Claims] 1. An aramid fiber non-woven substrate laminate comprising an aramid fiber non-woven fabric obtained by adhering a web with a solvent-soluble adhesive and a matrix resin. 2. The laminate according to claim 1, wherein the matrix resin is an epoxy resin.