GB2093468A - Polyphenylenesulphide Sheet- like Material - Google Patents

Abstract

A sheet-like material comprises a composition mainly consisting of high molecular weight poly p-phenylene- sulfide, characterised in that: a) the amount of extract thereof through chloroform extraction is less than 1.5 weight % of the total weight prior to said extraction, and b) i. the index of crystallinity thereof is in the range above 2.5 and below 8.0, ii. the size of crystallite thereof is in the range above 50 ANGSTROM and below 100 ANGSTROM , and iii. orientation factors thereof measured in three directions of through, Edge and End are respectively above 0.70, as measured by wide angle X-ray diffraction method. The sheet-like material may be laminated to a thin metallic film to produce a printed circuit board.

Description

SPECIFICATION Polyphenylenesulfide Sheet-like Material The present invention relates to a sheet-like material mainly consisting of poly p-phenylenesulfide (referred to as PPS hereinbelow), and also to a printed circuit board or substrate employing said sheetlike material.

Conventionally, for a raw material of a flexible printed circuit board, there has been widely employed a polyimide film owing to its superior thermal endurance. The polyimide film as described above, however, has such drawbacks that it is not only extremely expensive, but is generally weak against strong alkali such as aqueous sodium hydroxide and the like to be used in the manufacturing process of the printed circuit board, with a large moisture absorbance, thus being accompanied by dimensional changes following variations in the humidity.

On the other hand, the PPS formed into a sheet-like configuration having a small moisture absorbance has superior performance in the points such as insulating resistance, thermal endurance, resistance to chemical, etc., and draws attention as a raw material for printed circuit boards such as flexible circuit boards or carrier tapes for IC chips. Particularly, the unstretched PPS film produced by heating and crystallizing substantially unoriented films is simple in its manufacturing process, and essentially has no residual strain resulting from the stretching, without any dimensional variations due to heat shrinkage even when subjected to high temperature atmosphere, and therefore, is considered to be suitable for a substrate of printed circuit boards.

However, since the conventional unstretched PPS film has the disadvantages as described hereinbelow, it can not be applied to end uses requiring flexibility for a long period of time or including boring in the process, and thus, extremely limited in the range of applications thereof under the present circumstances.

More specifically, the disadvantages of the known unstretched PPS film have been such that, in the first place, the flexibility thereof as represented by the folding endurance is not sufficiently good even immediately after manufacture, while such flexibility is undesirably reduced to a large extent as the time elapses, and therefore, it has been difficult to maintain the favorable flexibility for long periods.

Secondly, since conventional unstretched PPS films are fragile and weak against impacts, cracks tend to be formed around the peripheries of bores or holes, and in some cases the films are broken at such cracks when such boring is effected by punching or drilling, Accordingly, it is an object of the present invention to provide an improved unstretched PPS sheet-like material superior in flexibility and impact resistance with substantial elimination of disadvantages inherent in the conventional unstretched PPS films of the kind.

Another object of the present invention is to provide an improved printed circuit board which utilizes the improved unstretched PPS sheet of the above described type.

According to the present invention, there is provided a sheet-like material comprising a composition mainly consisting of high molecular weight poly p-phenylenesulfide, characterized in that: a. the amount of extract thereof through chloroform extraction is less than 1.5 wt% of the entire weight prior to said extraction, and b. i) index of crystallinity thereof is in the range above 2.5 and below 8.0.

ii) Size of crystallite thereof is in the range above 50 A and below 100 A, and iii) orientation factors thereof measured in three directions of through, Edge and End are respectively above 0.70, as measured by wide angle X-ray diffraction method.

Further, according to the present invention, there is also provided an improved printed circuit board which comprises the improved PPS sheet-like material as described above, and metallic thin film or layer laminated thereon.

The high molecular PPS to be employed in the present invention is required to contain the recurring unit as represented by a structural formula

by more than 90 molar %, and more preferably, more than 95 molar %. If such para-oriented phenylenesulfide unit is less than 90 molar %, sufficient crystallinity of polymer is not available, while it is difficult to obtain a superior film due to poor thermal endurance during soldering, etc.

With respect to the remaining less than 10% of the recurring unit of said polymer, it is permissible to contain the metha-oriented unit

ether unit

sulfane unit

biphenyl unit

naphthalene sulfide unit

displaced phenyl sulfide unit

where R represents alkyl group, nitro group, phenyle group, alcoxide group), three functional phenyl sulfide unit

etc., to such a range as not to largely affect the crystallinity, stretchability and orientation efficiency of the polymer, but the comonomers thereof should more preferably be less than 5 molar %. Particularly, it is preferable that the multi-functional comonomers of more than three functions should be less than 1%.

Additionally, it is necessary that the apparent melt viscosity of said polymer should be in the range between 2000 and 100,000 poise, and preferably, between 3000 and 50,000 poise under the conditions of 3000C in temperature and 200 (seconds)-' in shear rate, and further that the non Newtonian coefficient (referred to as N value hereinbelow) under the above stated conditions should more preferably be in the range between 0.9 and 2.0.Polymers with extremely higher or lower viscosities are not only unpreferable from the viewpoints of uniformity during extrusion, surface state of the film obtained, etc., but give rise to extreme difficulties during the biaxial stretching, while they are not preferable due to the facts that, when the content of crosslinking or content of branching is high, with the N value exceeding 2.0, efficiency of orientation, thickness variation and surface roughness, etc. through stretching are adversely affected.

Although there is no perfectly sole relation between the apparent melt viscosity and N value, and the so-called "melt flow index" (referred to as MFI hereinbelow) generally employed as an index for melting viscosity of resins, the MFI of the PPS which may be used in the present invention is in the range approximately between 10 and 130.

On the other hand, with respect to the degree of polymerization, exact values thereof are not available, since measurements are difficult to be taken due to no solubility of PPS in the general organic solvents at normal temperature, with marked differences according to compositions of comonomers and degrees of crosslinking, etc., but the values may be regarded to be in the region approximately from 50 to 1000.

Addition of additives such as anti-oxidants, thermostabilizer, lubricants, nucieation agents, ultraviolet absorbers, colorants, etc. to the PPS employed in the present invention to the extent normally accepted, will invite no particular problems. Moreover, blending or mixing of small amounts of other kind polymers and fillers to the PPS of the present invention within the range not to hinder the object thereof for the purpose of improvement of fluidity, fine adjustment of crystallinity and the like, presents no inconveniences, either.

However, in cases where the sheet according to the present invention is to be used as electrical insulating materials, extra care should be taken in the preparation of PPS resin and selection of the additives so as to avoid reduction of insulation resistance. Although the PPS itself possesses an extremely favourable electrical insulation resistance ranging from low temperatures to high temperatures, such electrical resistance is undesirably decreased to a marked extent, if any substance which serves as carrier for electrical conduction (for example, metallic ion or the like) is contained therein. Accordingly, for the preparation of polymers, it is essential to carefully remove carrier substances such as metallic ion, etc., and simultaneously, not to cause such substances to be externally added or mixed.

In the sheet-like material of the present invention, it is required that the amount of extract when extraction by chloroform is effected under the conditions as stated later, is less than 1 5 wt% (more preferably, less than 1.2 wt%) of the entire weight before the extraction. The sheet-like material having such extraction amount exceeding 1.5 wt% is poor in flexibility and impact strength, with these properties being remarkably deteriorated as time elapses, and therefore, the object of the present invention can not be achieved thereby.

Although it is not clear why the PPS sheet having the high extraction amount as described above is inferior in the flexibility and impact strength, this may be assumed to be attributable to the fact that, in the amorphous region of the heated and crystallized sheet to support the flexibility and impact strength, the crystallites of low molecular weight composition, which are to be extracted by chloroform, are formed, thus resulting in loss of such flexibility and impact strength.

The crystalline structure of the sheet-like material according to the present invention is characterized by the following three sets of parameters as measured through the wide angle X-ray diffraction method.

Firstly, index of crystallinity must be in the range above 2.5 and below 8.0 (more preferably, above 3.0 and below 6.0). The index of crystallinity as referred to above may be defined by the ratio (1200/125) of the maximum intensity (1200) of diffraction peak with a Miller indices of (200) of PPS crystal in the wide angle X-ray diffraction profile of the sheet, to the intensity (125) at 20=250 at the same profile. If the index of crystallinity as described above is less than 2.5, the mechanical strength in the high temperature atmosphere such as solder bath is low, with poor thermal endurance, while, when the index of crystallinity exceeds 8.0, the resultant sheet becomes brittle or fragile, with loss of the flexibility and impact strength.

Secondly, sizes of PPS crystallites within the sheet (referred to as ACS hereinbelow) must be in the region above 50 A and below 100 . The size of the crystallite referred to above means the apparent size of crystallite to be obtained by applying the Scheller's formula to the half width of the diffraction peak with a Miller indices of (200) of the PPS crystal. If the ACS is less than 50 , poor thermal endurance may result, while any sheet having ACS value exceeding 100 A is difficult to be obtained actually.

Thirdly, it is also required that the orientation factors as measured in three directions of through, Edge and End (referred to as OF hereinbelow) must respectively be above 0.70. The orientation factor as measured in a certain direction as referred to above, is defined by the ratio 14=300/14=00 of photo density (I0=0 ) obtained by such procedures as taking X-ray plate image by Laue method through Xray incidence in said certain direction and scanning (200) diffraction ring of the PPS crystal by a microphotodensitometer in the radial direction along the equatorial line, with respect to photo density (I0=30 ) obtained in the similar manner in a direction of 300.

Meanwhile, the Trough direction referred to above is represented by the direction perpendicular to the sheet surface, Edge direction, by the direction parallel to the sheet surface and also to the transverse direction of said sheet, and End direction, by the direction parallel to the sheet surface and also to the longitudinal direction of said sheet. If the value of OF as described above is less than 0.7, the heat shrinkage is liable to take place due to the residual strain following the stretching.

Subsequently, the method of manufacturing the sheet according to the present invention will be explained hereinbelow.

In the first place, the PPS polymer to be employed for the production of the sheet-like material according to the present invention may be obtained by causing alkali metal sulfide to react with paradihalobenzene in polar organic solvents under high temperature and high pressure. Particularly, it is preferable to cause sodium sulfide to react with p-dichlorobenzene in amide type high boiling point polar organic solvents such as N-methyl-pyrrolidone, etc. In the above case it is most desirable to effect the reaction at the temperatures of 2300C to 2800C through addition of the so-called polymerization modifier such as caustic alkali, alkali metal carboxylate for the adjustments of the degree of the polymerization.The pressure in the autoclave and time for the polymerization may be suitably determined according to the kinds and amounts of modifiers to be employed and the desired degree of polymerization, etc. For maintaining electrical insulation performance of the film to be finally obtained, it is desirable to wash the polymerized polymer (generally in the form of powder) with water not containing metallic ion so as to remove by-produced salt, polymerization modifiers, etc, thereby to keep the ionic carrier concentration sufficiently small. In the above case, the total ash in the polymer should preferably be less than 5000 ppm, with calcium being less than 1000 ppm and sodium less than 500 ppm.

The PPS polymer thus obtained is fed to a known melt extrusion equipment represented by an extruder so as to be formed into the sheet-like configuration, but in the case where a larger amount of chloroform extract is contained in the polymer, the extraction amount thereof with respect to the sheet-like material does not fall in the range as defined by the present invention, and thus, only the sheet-like material poor in the flexibility and impact strength is to be obtained.

In the case as described above, it is desirable to preliminarily treat the polymer before supplying to the forming process. For this purpose, there may be employed, for example, a method by which the polymer powder obtained by to the polymerization and washing with water is further washed or rinsed in a suitable organic solvent maintained at temperatures higher than room temperature (preferably higher than 500C) under normal or increased pressure. The organic solvents to be employable in the above treatment may, for example, be methylene chloride, NMP, chloroform, toluene, etc. Similarly, acetone heated to a temperature close to the boiling point may also be employed.

During formation of PPS polymer into the sheet-like configuration by the melt extrusion equipment, the PPS in the melted state is liable to be subjected to gelation through contact with oxygen, and therefore, it is desirable to substitute the interior of the hopper of the extruder, etc. by inert gas or to reduce the pressure therein.

The melted resin is continuously extruded from slit-shaped dies (for example, T die, circular die, etc.) so as to be forcibly cooled. As means for such forcible cooling, a process for casting onto a cooled metallic drum, a process for spraying gas or liquid at low temperatures, or a process for immersing in a liquid at low temperature or the like may be employed selectively or in combination.By the forcible cooling as described above, the PPS in the melted state is rapidly cooled down to a temperature below the glass transition temperature for once forming it into the sheet in the unoriented and amorphous state. Prior to or during the forcible cooling, stretching the sheet in the longitudinal direction or transverse direction or in the both directions not only presents no problem, but also is rather preferable from the viewpoints of flexibility and impact strength, as far as the OF of the sheet finally obtained is limited to the values above 0.70.However, in general, such stretching should be effected under the state where the temperatures of the sheet are higher than 220 to 2300 C. For one example, there may be raised a method in which, immediately after the extrusion of PPS from the circular die, stretching of 3 to 10 times with respect to the area is applied through utilization of air pressure (the so-called blowup method).

In the manner as described above, the formed material in the configuration of a sheet as an intermediate product is obtained. The "sheet-like material" according to the present invention means a thin-leaf like formed material less than approximately 5 mm in thickness, and generally represents formed items normally called films, sheets, plates, etc.

Subsequently, constant dimensional heat set is effected for the purpose of improving the thermal endurance. The "constant dimensional heat set" according to the present invention means a heat treatment under such conditions that the dimensional variation before and after the heat treatment becomes below +20%.

The heat-treatment as described above is effected by bringing the sheet to be treated into contact with the flow of heated liquid or gas or with surface of a solid. (The "temperature" and "time" for the heat treatment to be mentioned later are nothing but the temperature and contacting time of such heating medium). More specifically, the examples of such heat treatment may include a process for bringing into contact with a heated roll (referred to as the roll heat treating method hereinbelow), a method of employing a tenter, a process for blasting heated air flow on a roll, etc.

The temperatures for the above heat treatment are set in the range between above 1 500C and below 2800 C. Temperatures below 1 500C are not preferable, since there is a possibility that the ACS of the sheet to be obtained becomes less than 50 A, while on the other hand, if the temperature exceeds 2800 C, it becomes difficult to effect the heat treatment by the method earlier described, since the sheet-like material to be treated tends to lose its shape due to softening.

Meanwhile, although the time for the heat treatment is one of the main factors for determining the index of crystallinity, the index may also vary according to the properties of the polymer employed, and methods and time for the heat treatment, so it is required to adjust so that the index of crystallinity falls into the range as described earlier.

In the next step, for obtaining the printed circuit board according to the present invention, it is a general practice to apply a metallic foil represented by a copper foil onto the sheet-like material obtained by the above described method through employment of a suitable adhesive or to employ a method for forming a metallic layer on the surface of the sheet through processes such as plating or vacuum metallizing, etc., but alternatively, there may be employed another method in which a laminated material of PPS and metallic foil is produced either by applying PPS onto the metallic foil through extrusion laminating or by fusing together the PPS sheet and the metallic foil by heat pressing, and thereafter, is subjected to heat treatment for crystallization of the PPS.

As a result of the construction of the sheet-like material of the present invention as described above, the insufficient "flexibility", "impact strength" and "aptitude for boring" which are the disadvantages inherent in the conventional PPS unstretched films, have been remarkably improved, and thus, the improved sheet-like material with extremely high reliability has been advantageously presented in the applications thereof, for example, to a printed circuit board accompanied by boring and bending or folding processes.

Furthermore, the printed circuit board according to the present invention is superior also in the electric characteristics of high frequencies as well as in the resistance to chemicals, resistance to moisture, flexibility, aptitude for boring, and thermal endurance, and such a printed circuit board well balanced in various characteristics as that according to the present invention has not been conventionally proposed as yet.

Subsequently, description will be given hereinbelow on the definition of the characteristic values of the polymer and sheet-like material employed in the present invention, and also on the measuring and evaluating methods thereof.

(1) Amount of Extraction by Chloroform Approximately 10 g of the sample cut into square pieces each about 1 cm in length and width are accurately measured by a chemical balance, and the weight is represented by Ag.

Subsequently, the sample thus measured is set in a Soxhlet extractor containing about 100 cc of chloroform for extraction by a hot water bath of 650C for 24 hours.

Thereafter, the extracted liquid is transferred into a weighing bottle (the weight thereof is represented by Bg) accurately weighed in advance, with further addition thereto of a primary washing liquid obtained by washing the interior of the extractor by a small amount of chloroform for subsequent drying in a hot air oven at a temperature of 300C until the liquid disappears. In the next step, after transfer into the hot air oven at 650C and drying for one hour, the sample is cooled down to the room temperature in a desiccator containing silica gel and subsequently, accurately weighed by the chemical balance (the weight is represented by Cg).

The results thus obtained are applied to the following equation so as to obtain the amount of extraction Wex (wt%).

Wex=1 00 (C-B)/A (2) Wide Angle X-ray Diffraction Method OF: With each of the samples being aligned in the stretching direction and formed (for fixing each film during the formation, 5% amyl acetate solution of collodion is employed) into a strip 1 mm thick, 1 mm wide and 10 mm long, X-ray was directed so as to be incident along the surface of the film (in the Edge and End directions) for taking the X-ray plate image photograph. For the X-ray generating apparatus, Model D-3F unit made by Rigaku Danki was employed, with Cu-Kd rays passed through an Ni filter at 40 kV-20 mA being employed as the X-ray source. The distance between the sample and film was set at 41 mm, and multi-exposure method (15 inchs. and 30 mins.) was adopted by the use of the kodak non-screen type films.

In the next step, and the orientation degree (OF) each sample was defined to be OF=145=30 /lfi=0 by reading the photo density of diffraction peak with a Miller indices of (200) on the X-ray plate image photograph, through scanning by a densitometer in a radial direction from the center of the plate image at the positions of 0=0 (on the equatorial line) 100, 200 and 300, wherein l0=30 shows the maximum intensity of scanning at 300 and I=00 represents the maximum intensity at the scanning of the equatorial line.

It is to be noted here that the average values of strength of 0=0 and 6=180 were employed for lb=0 , and those of strength of 0=30 and =1 500, for l=300.

In connection with the above, the measuring conditions of the densitometer are as follows.

For the apparatus, Sakura micro-densitometer model PDM-5 type A made by Konishiroku Photo Industry Co. was employed with the measuring density range of 0.ON4.OD (minimum measuring area 4 82 conversion), optical magnifications of 100 times, slit width of 1 , and height of 100 , while the film moving speed is 50 y/sec at chart speed of 1 mm/sec.

ACS and index of crystallinity: For cancelling the orientation effect of the sample, the method of rotating the sample in a plane was adopted and the diffraction pattern was measured by the refraction method. As the X-ray generating apparatus, Model D-8C unit made by Rigaku denki was used, while Cu-Kd passed through the Ni-filter at 35 kV-1 5 mA was employed as the X-ray source. For the goniometer, Model PMG-A2 unit made by Rigaku denki was employed, and the sample was mounted on a rotary sample table rotatable at the speed of 80 rpm, with Divergence slit 1 0, receiving slit 0.15 mm and scattering slit 1 being employed for the slit system, The 26 scanning speed was 1 0/mien., while the chart speed was 1 cm/min.Each of the samples was cut into a square having 1 side of 20 mm, and was piled up into thickness of 0.5 mm for preparing the measuring specimen.

From the half width of the diffraction peak with a Miller indices of (200), the apparent crystal size (ACS) was worked out by the employment of Scheller's formula.

ACS( )=KA/p cos0, = [ B2-( B' )2j112 Where K: Scheller constant (K=1) A: X-ray wave length (A=1.5418 ) 26: Bragg angle ( ) ; p: Half width after correction (radian) B: Actually measured half width B': Half width of correcting standard sample (Si single crystal).

Meanwhile with respect to the index of crystallinity from the diffraction profile of each sample, the maximum intensity (1200) at the diffraction peak with a Miller indices of (200) and the intensity (125) at 26=250 as internal standard, were measured with the ratio therebetween being defined as the index of crystallinity (1200/125).

(3) Apparent Melt Viscosity (,uo) and Non-Newtonian Coefficient (N) With the use of an extrusion plastometer type viscometer having the capillary shaped die of length L and radius R, when the output by volume, upon extrusion of the polymer under pressure of P and at temperature T, is represented by 0, the apparent shear stress (tau) apparent shear rate y and apparent viscosity y are defined as follows.

T=(RP)/(2L) y=j4Q)/(7rR2) =Tiy- In the above case, the apparent melt viscosity yo is defined by the value at y=200 (sec)-1, of a curve y=f(y) to be obtained through plotting of we at the time with respect to various y.

On the other hand, the non-Newtonian coefficient N is defined by the reciprocal of the value at y=200 (sex)~' of d log g (y)/d log y which is the full logarithmic differential function of a curve T=9(P) to be obtained by plotting T with respect to various y. The value N as described above is equal to the index n, on the assumption that the relation between the shear stress S and shear rate D of the melt polymer (the so-called flow curve) may be approximated by a formula D=aS" (a and n are constants).

In the present invention, the value measured atT=3000C was adopted with the employment of a die of L=1 0 mm and R=0.5 mm.

(4) Glass Transition Temperature (Tg) and Melting Point (Tm) These were measured by the DSC method, while Tm was defined by the peak temperature of the melting curve.

(5) Tensile Strength, Elongation According to the method set forth in JIS z 1702, measurements were taken by the employment of a tensile tester of "Instron" type.

(6) Heat Shrinkage A. To cut the sample film into ribbon-like shape each measuring 10 mm in width and 250 mm in length.

B. To draw 2 marked lines in the transverse direction in parallel relation to each other at an interval of about 200 mm, and accurately measure the interval between the marked lines with the use of a casedometer (to be Amm).

C. To place the above sample into the hot air oven at 2500C, with a load of 1 g being applied to the forward end of said sample, and to take out the sample after leaving it to stand in the oven for 10 minutes.

D. To measure the interval between the 2 marked lines again with the use of the casedometer (to be Bmm).

E. To define the heat shrinkage (%) by 100 (A-B)/A.

(7) Folding Endurance The number of folding endurance at 200C was measured according to the method set forth in JIS P-8 115 (the so-called MIT method).

(8) Rate of Defects in Boring Process A. In the case of sheet With the sheet cut into tape-shape of 35 mm in width and 10 m in length, sprocket perforations of carrier tape for IC chips are formed at opposite sides of the tape by employing a punching machine for the carrier tapes for IC chips. Thereafter, by counting the number of perforations formed with cracks at the peripheral edges thereof through visual examination, the rate of defects in the boring process is defined by the rate thereof with respect to the total number of perforations.

B. In the case of a printed circuit board substrate by using a drill of 1 mm in diameter, 1000 holes or bores are formed in the substrate from the metallic foil side thereof in a checkerboard-like pattern at intervals of 10 mm, and thereafter, the number of holes having cracks at their peripheral edges is counted through visual examination so as to define the rate of defects in the boring process by the rate thereof with respect to the total number of holes.

(9) Solderability A. In the case of a sheet The film cut into squares each 50 mm in length and width is floated on a solder bath kept at a temperature of 2500C for observation of dimensional stability at this time. Thereafter, by applying a tension of approximately 0.5 kg/mm2 to the opposite edges of the film in the solder bath for visual examination of the degree of elongation at that time.

The results of the evaluation are to be represented by the following 4 grades.

O: Dimensional stability is favorable, with almost no elongation.

n: Although favorable in dimensional stability, elongation is large.

M: Elongation is small, but poor in dimensional stability.

X: Poor in dimensional stability, with large elongation.

B. In the case of a printed circuit board substrate.

The evaluation is effected according to the method set forth in JIS C-6481, and swelling and peeling on the film surface and copper foil surface were visually examined.

The results of the evaluation were represented by the following grading.

0: Neither swelling nor peeling is noticeable.

X: Both swelling and peeling are noticeable.

(10) Resistance to Chemicals The evaluation was effected according to the method set forth in Test Methods Manual No. 2, 3, 2, of IPC (Institute of Printed Circuits), and the indications were made as follows according to the residual or retention rate of peeling off strength.

O: Residual rate more than 80% inclusive X: Residual rate less than 80%.

Hereinbelow, Examples are inserted for the purpose of explaining the present invention, without any intention of limiting the scope thereof.

Example 1 (1) Polymerization of PPS A. Polymerization of the high molecular weight PPS (set to be PPS-A) employed in the present invention 32.6 kg of sodium sulfide (250 mol, containing water of crystallization at 40 wit%), 100 g of sodium hydroxide,18.0 kg (125 mol) of sodium benzoate, and 79.2 kg of N-methyl-2-pyrrolidone (referred to as NMP hereinbelow) were placed into an autoclave, and gradually raised in temperature up to 2500C, while being stirred so as to remove distillant liquid of 7.0 1 containing water of 6.9 kg.

Subsequently, 37.5 kg (255 mol) of 1,4-dichlorobenzene (referred to as DCB hereinbelow) and 20.0 kg of NMP were added to the remaining mixture for heating at 2500C for 3 hours. The reaction product was subjected to extraction in methylene chloride at 380C for 2 hours, with further 8 times washing in hot water, and then, dried at 800C for 24 hours by using a vacuum dryer, and thus,21.9 kg of high molecular weight PPS (yield 81%) with apparent melt viscosity of 4200 Poise, N value of 1.6, Tg of 91 C and Tm of 2800C was obtained.

B. Polymerization of PPS (referred to as PPS-B) for comparison In the similar procedures as described above, polymerization was effected for 5 hours at 2650C for further 8 times washing by hot water without conducting methylene chloride extraction, and subsequent drying, and thus, approximately 20 kg of dried PPS having the apparent melt viscosity of 3500 Poise, N value of 1.6, Tg of 880 C, and Tm of 2790C was obtained.

(2) Thermofonning PPS-A and PPS-B obtained by the processes as described in the above item (1) were each fed to an extruder of 40 mm and melted at a temperature of 31 00C, and then, extruded from a T die having a linear lip of 600 mm in length and 0.2 mm in clearance so as to be cast onto a metallic drum kept at a surface temperature of 650C for cooling and solidification, and thus, amorphous films A-1 and B-1 of 550 mm in width and 50 Mm in thickness were obtained (cast method).

Meanwhile, PPS-A and PPS-B were each supplied to an extruder of 38 mm) for melting at a temperature of 31 00C, and then, extruded from a circular die of 50 mm in diameter and 0.5 mm in clearance. Immediately thereafter, air is directed into the melted film tube for blowing 10 times in area for subsequent rapid cooling by air stream, and thus, amorphous films A-2 and B-2 of 250 mm in width and 50 Mm in thickness were obtained (tubular method).

(3) Heat Treatment The amorphous films A-1, A-2, B-1 and B-2 were each subjected to heat treatment with the use of a tenter at 2600C for 30 seconds, and thus films A-1-1, A-2-1, B-1 -1 and B-2-1 were obtained.

(4) Properties of the Films Obtained Table 1 shows the properties of the films obtained. More specifically, films A-1 -1 and A-2-1 are those according to the present invention, while films B-1 -1 and B-2-1 are films other than those according to the present invention.

Table 1 Chloroform extracted OF Film PPS amount ACS Index of symbols employed (wit%) Through End Edge (A) crystallinity A A 0.71 0.89 0.94 0.91 72 5.1 A-2-1 A 0.69 0.95 0.80 0.79 70 -5.4 B B 1.98 0.90 0.96 0.89 73 5.5 B-2-1 B 1.95 0.96 0.81 0.82 74 5.7 (5) Evaluation Table 2 shows the results of evaluation of the above described films.

As is clear from Table 2, the films according to the present invention are superior not only in the mechanical properties and dimensional stability at high temperatures, but also in the flexibility and aptitude for boring which have been related to the drawbacks of the conventional films, while having less deterioration in the flexibility and aptitude for boring with time. On the other hand, the known films having a large chloroform extraction amount are poor in the flexibility and aptitude for boring.

Table 2 Evaluation results Sample film A-1-1 A-2-1 B-1-1 B-2-1 Tensile strength 8.0 8.5 7.8 8.1 (kg/mm2) (MD) Elongation (%) 7.4 7.1 6.5 6.6 (MD) Heat shrinkage (%) 0.4 0.5 0.5 0.5 (MD) Folding Immediately 5200 6500 900 1300 endurance after (times) manufacture 1000C,after 3600 4300 440 670 30 days Rate of Immediately 0 0 1.3 0.9 defects after in boring manufacture process (%) 1000C, after 0 0 1.7 1.5 (punching) 30 days Remarks Present Present Comparative Comparative invention invention item item Example 2 (1) Amorphous Film The amorphous film A-1 used in Example 1 was employed.

(2) Heat Treatment The amorphous film A-l was subjected to heat treatments at various temperatures for different periods of time with the use of the tenter, and thus, films A-l NA-1 -5 having different index of crystallinity and ACS were obtained.

(3) Properties and Evaluation Results of the Films Obtained.

Table 3 shows the properties and evaluation results of the resultant films.

In table 3, it is indicated that even if the chloroform extraction amount is small, films with superior properties are difficult to be obtained so far as the 3 sets of parameters by the wide angle Xray diffraction are not within the specific range.

Table 3

------------------------------------------------------------------------------------------------------ ltem Unit A-1-1 A-1-2 A-1-3 A-1-4 A-1-5 ------------------------------------------------------------------------------------------------------ Heat tresting temporature C 260 260 277 130 270 Heat treating time Second 30 2 3600 30 60 ------------------------------------------------------------------------------------------------------- Chloroform extraction Wi% 0.71 1.1 0.62 1.0 0.69 Amount OF Through 0.89 0.87 0.85 0.95 0.87 End 0.94 0.96 0.95 1.00 0.96 Edge 0.91 0.88 0.84 0.97 0.90 ACS A 72 69 80 45 75 index of Grystallinlty 5.1 2.0 8.5 2.5 5.3 ------------------------------------------------------------------------------------------------------ Heat shrinkage rate 0.4 0.8 0.3 0.7 0.4 Folding endurance 5200 8300 240 2600 4900 (immediately after manufacture) Solderability 0 x 0 x 0 ------------------------------------------------------------------------------------------------------ Remarks Present Comparative Comparative Comparative Comparative Comparative invention item item item item item ------------------------------------------------------------------------------------------------------ Example 3 (1) Raw Material PPS-A used in Example 1 was employed.

(2) Thermoforming PPS-A was formed by the tubular method in the item (2) of Example 1. In the above case, 3 kinds of dies prepared by making the slit clearances of circular dies respectively into 0.4 mm, 0.8 mm and 2.5 mm were employed, through blowing 8 times,16 times and 50 times in the respective areas, and thus, 3 kinds of films (to be A-3, A-4 and A-5) each 50 ym in thickness were obtained.

(3) Heat Treatment Amorphous films A-3, A-4 and A-5 were respectively subjected to heat treatments with the use of the tenter at 2700C for 120 seconds, and thus, films A-3-i , A-4-1 and A-5-1 were obtained.

(4) Properties and Evaluation Results of the Films Obtained Table 4 shows the properties and evaluation results of the resultant films.

In table 4, it is indicated that in the films with small OF, the heat shrinkage is increased by the residual strain due to orientation, and thus, the superior features as unstretched films are undesirably lost.

Table 4 Sample film Items A-3- 1 A-4- 1 A-5- 1 Chloroform extraction 0.73 0.71 0.70 amount (wt%) OF Through 0.89 0.93 0.92 End 0.86 0.76 0.61 Edge 0.85 0.75 0.59 ACS 76 75 72 Index of crystallinity 5.2 5.9 7.0 Heat shrinkage rate (%) 0.3 0.5 1.6 Folding endurance (times) 6000 6100 4600 Solderability o o Remarks Present Present Present invention invention invention Example 4 (1) Base Film PPS film (A-l-l) according to the present invention and comparative film (B-1-1) used in Example 1 were employed.

(2) Preparation of a Printed Circuit Board Substrate a. In the first place, the base film was subjected to the electrical corona treatment by impressing thereto electrical energy of 3000 joule per 1 m2 of the film.

b. Subsequently, an adhesive mainly composed of dimer acid group polyamide ("Milbex" 1200) was coated into a thickness of 20 m (after drying) with the use of a reverse coater.

c. In the next step, with an electrolytic polished Cu foil (35 m in thickness) for printed circuit board substrates being piled up thereon, the film was passed through a press roll having a linear pressure of 3 kg/cm, and maintained at a temperature of 1 000C for lamination.

d. The laminated material thus obtained is left to stand in the hot air oven at 800C for 4 days so as to harden the adhesive, and thus, the substrate for printed circuit board was obtained.

(3) Results of Evaluation Table 5 shows the results of evaluation.

In table 5 it is indicated that, in the printed circuit substrate according to the present invention, the aptitude for boring, which is related to the drawbacks of the conventional substrates employing known PPS unstretched films, has been improved, while the superior resistance to chemicals and thermal endurance specific to the substrates using PPS films are sufficiently maintained.

Table 5 Base film Evaluation item A-1-1 B-1-1 Rate of defects in boring 0 2.1 process (%) (drilling) Resistance to chemical Alcohol o o Hydrocarbon o o Ketone o o Chlorinated o o Solvent o o Acids o o Base o o Solderability o o Claims (Filed 25 March 1981) 1.A sheet-like material comprising a composition mainly consisting of high molecular weight poly p-phenylenesulfide, characterised in that: a) the amount of extract thereof through chloroform extraction is less than 1.5 weight % of the total weight prior to said extraction, and b) i. the index of crystallinity thereof is in the range above 2.5 and below 8.0, ii. the size of crystallite thereof is in the range above 50 A and below 100 A, and iii. orientation factors thereof measured in three directions of through, Edge and End are respectively above 0.70, as measured by wide angle X-ray diffraction method.

2. A material according to Claim 1 in which the poly p-phenylene-sulfide as represented by the recurring unit

comprises more than 90 molar % of the composition.

3. A material according to Claim 1 in which the poly p-phenylene-sulfide as represented by the recurring unit

comprises more than 95 molar % of the composition.

4. A material according to any of Claims 1 to 3 in which recurring units derived from comonomers having more than three functions comprise less than 1 molar %.

5. A material according to any of Claims 1 to 4 in which the apparent melt viscosity of the polymer is between 2,000 and 100,000 poise at 3000C and 200 (seconds)-' shear rate.

6. A material according to Claim 5 in which the polymer has an apparent melt viscosity of between 3,000 and 50,000 poise at 3000C and 200 (Seconds)-1 shear rate.

7. A material according to any of Claims 1 to 6 in which the non-Newtonian coefficient of the polymer at 3000C and 200 (seconds)-1 shear rate is in the range 0.9 to 2.0.

8. A material according to any of Claims 1 to 7 in which the melt flow index of the polymer is in the range 10 to 130.

9. A material according to any of Claims 1 to 8 in which the amount of extract thereof by chloroform extraction is less than 1.2 weight % of the total weight prior to extraction.

10. A material according to any of Claims 1 to 9 in which the index of crystallinity is between 3.0 and 6.0.

11. A sheet-like material substantially as herein described.

12. A method of producing a high molecular weight sheet-like material comprising reacting an alkali metal sulfide with a para-dihalobenzene in a polar organic solvent under conditions of high temperature and pressure so as to produce a composition as claimed in any of Claims 1 to 11.

13. A method according to Claim 12 in which the sulfide is sodium sulfide.

14. A method according to Claim 12 or 13 in which the para-dihalobenzene is p-dichlorobenzene.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (19)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   Table 5 Base film Evaluation item A-1-1 B-1-1 Rate of defects in boring 0 2.1 process (%) (drilling) Resistance to chemical Alcohol o o Hydrocarbon o o Ketone o o Chlorinated o o Solvent o o Acids o o Base o o Solderability o o Claims (Filed 25 March 1981) 1.A sheet-like material comprising a composition mainly consisting of high molecular weight poly p-phenylenesulfide, characterised in that: a) the amount of extract thereof through chloroform extraction is less than 1.5 weight % of the total weight prior to said extraction, and b) i. the index of crystallinity thereof is in the range above 2.5 and below 8.0, ii. the size of crystallite thereof is in the range above 50 A and below 100 A, and iii. orientation factors thereof measured in three directions of through, Edge and End are respectively above 0.70, as measured by wide angle X-ray diffraction method.
2. 2. A material according to Claim 1 in which the poly p-phenylene-sulfide as represented by the recurring unit

   comprises more than 90 molar % of the composition.
3. 3. A material according to Claim 1 in which the poly p-phenylene-sulfide as represented by the recurring unit

   comprises more than 95 molar % of the composition.
4. 4. A material according to any of Claims 1 to 3 in which recurring units derived from comonomers having more than three functions comprise less than 1 molar %.
5. 5. A material according to any of Claims 1 to 4 in which the apparent melt viscosity of the polymer is between 2,000 and 100,000 poise at 3000C and 200 (seconds)-' shear rate.
6. 6. A material according to Claim 5 in which the polymer has an apparent melt viscosity of between 3,000 and 50,000 poise at 3000C and 200 (Seconds)-1 shear rate.
7. 7. A material according to any of Claims 1 to 6 in which the non-Newtonian coefficient of the polymer at 3000C and 200 (seconds)-1 shear rate is in the range 0.9 to 2.0.
8. 8. A material according to any of Claims 1 to 7 in which the melt flow index of the polymer is in the range 10 to 130.
9. 9. A material according to any of Claims 1 to 8 in which the amount of extract thereof by chloroform extraction is less than 1.2 weight % of the total weight prior to extraction.
10. 10. A material according to any of Claims 1 to 9 in which the index of crystallinity is between 3.0 and 6.0.
11. 11. A sheet-like material substantially as herein described.
12. 12. A method of producing a high molecular weight sheet-like material comprising reacting an alkali metal sulfide with a para-dihalobenzene in a polar organic solvent under conditions of high temperature and pressure so as to produce a composition as claimed in any of Claims 1 to 11.
13. 13. A method according to Claim 12 in which the sulfide is sodium sulfide.
14. 14. A method according to Claim 12 or 13 in which the para-dihalobenzene is p-dichlorobenzene.
15. 15. A method according to any of Claims 12 to 14 in which the solvent is an amide-type.
16. 1 6. A method according to any of Claims 12 to 15 in which the reaction temperature is 2300C to 280 C.
17. 17. A method according to Claim 16 in which the reaction is controlled by a polymerisation modifier.
18. 18. A method of producing a high molecular weight sheet-like material substantially as herein described.
19. 19. A printed circuit board comprising a sheet-like material as claimed in any of Claims 1 to 11 and a thin metallic film laminated thereon.