DE2424002C3 - Flame retardant multilayer printed circuit board and process for their manufacture - Google Patents

Description

The present invention relates to a position of a flame-retardant multilayer line

Flame-retardant multilayer printed circuit board and sub-board are specified.

: in process of their manufacture. The task is, starting from a difficult

flammable multilayer printed circuit board with two Outer layer metal circuits, at least one Inner layer metal circuit between the Outer layer circuits lies, and with insulating layers made of an at least partially hardened when-hardenable brominated epoxy resin, whereby the circuits adhere to one another by means of the respective insulating layers, according to the invention achieved in that at least the surface part of the insulating layer, the is in contact with the surface of the shiny side of the circuit, a bromine content of less than 10% by weight, and that the other part of the insulating layer has such a bromine content possesses that the total bromine content of the resin is greater than about 15 weight percent overall

In summary, the invention also provides a flame-retardant multilayer conductor plate two outer layer circuits, at least one inner layer circuit and insulating layers a cured thermosetting epoxy resin for connecting adjacent circuits, wherein at least that part of the surface of the insulating layers that corresponds to the surface of the shiny side of the Circuit connected, a bromine content of less than about 10 weight percent and the other part of the insulating layers has such a bromine content that the entire bromine content of the resin is greater than about 15 weight percent total based on the resin. The circuit board has excellent high temperature adhesive strength and good solder resistance.

The invention is explained in more detail below with reference to the drawing.

It shows

Fig. 1 is a section through a coated with copper Laminate,

F i g. FIG. 2 is a graph showing the relationship between the bromine content of the resin content in FIG Surface layer of a laminate and the high temperature adhesive strength of the laminate versus the copper foil,

F i g. 3 is a graph showing the relationship between the bromine content of the entire laminate and the resistance to fire and

F i g. 4 A to 4 H an embodiment of the inventive method for producing a flame-retardant multi-layer circuit board.

The invention is based on the knowledge that the high-temperature adhesion of a circuit metal foil and the thermal resistance to solder of the insulating layers become satisfactory when the halogen content of the resin component in the surface layer which is bonded to the metal foil is less than 10% by weight. From a practical point of view and for a difficult inflammability of the layer material, the thickness of the layer with such a low bromine content should not exceed about 30 μm. The adhesive strength does not increase, even if the thickness of the layer with the low bromine content exceeds 30 μm. On the other hand, a thickness of the layer with a low bromine content of at least ΙΟμίη is required in order to achieve sufficient adhesive strength for the copper foil. The laminate can be made flame retardant not only with bromine, but also with chlorine, although bromine is more effective than chlorine. It is essential in the invention to add a bromine compound, but a chlorine compound can also be provided along with the bromine compound.
That used in the present invention

Epoxy resin is generally, for example, a bisphenol-A epoxy resin, a resorcinol epoxy resin, a tetrahydroxyphenylethane epoxy resin, a novolac epoxy resin, a polyalcohol epoxy resin, a polyglycol epoxy resin, a glycerine triether epoxy resin, a polyolefin epoxy resin, an alicyclic epoxy resin or the like.

All previously used hardeners can be provided as hardeners for these epoxy resins, for example Amine hardener, acid anhydride hardener or the like.

As a halogen source for making the above-mentioned epoxy resins difficult to ignite For example, bromine-containing bisphenol A epoxy resins, bromine-containing novolac epoxy resins etc. are provided; however, it is also possible to combine these substances with other materials if necessary to mix, for example with fillers, phosphorus compounds, etc. Furthermore, as halogen-containing Hardener 4,4'-methylenebis (2-chloroaniline), 4,4'-methylenebis (2,3-dichloroaniline), 4,4'-methylenebis (2,3-dichloramline), 4,4'-methylenebis (2,5-dichloroaniline), Het. Acid anhydride, tetrabromophthalic anhydride, Tetrachlorophthalic anhydride, etc. can be used.

To make a low bromine layer on the surface layer covered with a metal foil of the layer material is connected, a prepreg is first made by adding a resin with a high bromine content is used, followed by a layer of a resin on the prepreg with a low bromine content is produced by a coating, spraying or dipping process.

The laminate can also be obtained by laminating a prepreg with a high bromine content and a low bromine prepreg.

The method according to the invention for producing a flame-retardant multilayer printed circuit board is characterized in that laminated materials laminated with a copper coating on both sides are produced that an inner layer circuit is formed on one side of the respective layer material is that several layers of at least one flame-retardant prepreg from one thermosetting epoxy resin are applied, wherein at least a surface part of the prepreg less than about 10 weight percent bromine and the other portion of the prepreg has a bromine content such that the total bromine content of the resin as a whole is greater than about 15 percent by weight, based on the resin, so that the layer with the low bromine content of the Pre-impregnation with the inner layer circuit surface may be in contact that the entire assembly is pressed to adhere the layers and that finally the resulting multilayer printed circuit board is drilled, non-Glavanese copper-clad, electrical copper-plated and the photo printing, a gold plating and a removal of the protective layer and etching residues is subjected to processes that have already been developed.

The following are comparative examples for the production of a copper-clad on one side Coating material described. At all

Comparative Examples are all parts and percentages in the same manner as in Comparative Example 1 weight related. are processed.

A varnish D with a bromine content of 4Vo, be-comparative example 1 _{based on the} solids content of the varnish, is made

50 parts of bisphenol A epoxy resin (epoxy equivalent of 5, 80 parts of bisphenol A epoxy resin and 20 parts 450 to 550, melting point 65 to 75 ° C), 50 parts of tetrabromobisphenol-A epoxy resin. Tetrabromobisphenol-A-epoxy resin (epoxy equivalent on the surface of the lacquer C (pre-

330 to 380) and 0.5 part of benzyldimethylamine as impregnate C) impregnated flat glass fabric, curing accelerators are applied in 80 parts of methyl lacquer D so that the ethyl ketone to be coated is dissolved. The resulting solution will have a thickness of 10 μm, which is mixed with 4 parts of dicyandiamide as hardener, in the same way as in Comparative Example 1, is dissolved in 20 parts of methyl cellosolve, thereby creating a B. -Step-epoxy pre-impregnation paint with a concentration of approximately 50% (pre-impregnation B) with a resin content of 60%. This varnish is referred to below as having a bromine content of 16%, based on the total “varnish / 4”. Its bromine content is 23% of the total resin content. As in the comparison with regard to the solids content of the paint. Example 1 are the epoxy prepreg and a

Then 100 parts of a bisphenol-A-epoxy copper foil are pressed under the action of heat to resin (epoxy equivalent 450 to 550, melting point a one-sided copper-clad epoxy layer-65 to 75 ° C) and 0.5 part of benzyldimethylamine as a substance with a thickness of 0.6 mm to be obtained, such as curing accelerator in 80 parts of methyl ethyl ketone ao this in FIG. 1 is shown. solved. The resulting solution is mixed with 4 parts _v .... . . .

Dicyandiamide ak hardener mixed in 20 parts of Comparative Example 3 Methyl cellulose is dissolved, creating a paint with 50 parts bisphenol A epoxy resin (as in Ver

a concentration of 50Vo is obtained. This same example 1), 50 parts of tetrabromisphenol A lacquer, is referred to below as "lacquer B". as epoxy resin (as in Comparative Example 1), 16.5 parts

A flat glass fabric with a thickness of unge-4,4'-methylbis (2-chloroaniline) as a halogen-containing approximately 100 μm and made of 60/25 mm warp threads and hardener and 1.0 part boron trifluoride monomethylaniin 58/25 mm weft is impregnated with the above-mentioned hardening accelerator in methylethyl lacquer A and then dissolved at 130 ° ClO min to form the ketone and the lacquer concentration is dried to a half-cured state (B stage). This represents 30, whereby a varnish E is obtained. The pre-impregnated material obtained from bromine is referred to below as “the pre-impregnation and chlorine content of the lacquer is 21 Ve and 3.7 ⁰ Zo, precise: A ”. The lacquer B is then referred to based on the solids content. Surface of the 100 parts bisphenol-A-epoxy resin to be connected with a copper foil (applied as in the case of the impregnated fabric so that the same example 1) and 16.5 parts 4,4'-methylenebis thickness of the top layer in the dry state at 35 (2 -cb.loramlin) as a hardener are in methyl ethyl ketone, for example, lOjim and then dissolved to dry a varnish F with a varnish concentration of 130 ° C for 10 minutes to produce the layer of 30Ve. Transfer the chlorine content of the varnish varnish B to the B stage. The amount obtained is 3.7Ve, based on the solids content. Pre-impregnation is referred to in the following as »pre-impregnation- In the same way as with the comparative example

gnat B «denotes the resin content of prepreg 1, a flat glass fabric is impregnated with varnish E gnats is 55 V · and the bromine content based on (prepreg E), and varnish F has the total resin content 19Ve. layered on the impregnated fabric around a

The glossy surface of a 105 μm thick B-stage epoxy prepreg (prepreg F) with copper foil is roughened with an etching solution which has a resin content of 60 Ve and a halogen content by dissolving 40 g of copper chloride and 500 ml 45 of about 21V, based on the total Harzge hydrochloric acid in water to 11 is obtained; to produce the copper stop. The prepreg F and a foil are then dipped into a 1 Votige aqueous solution of a copper foil with the action of heat on the aminosilane binder (Wz A 1100 from the US company in the same way as in Comparative Example 1. Uaion Carbide Caqy $ and then 30 ram In this way it was dried copper casings-100 ° C BneSduchl des VoränpTä ^ nats B 50 ter epoxy-Sdricfatwerkstoff ffiä a thickness of BDd ¹ BJeT Sejacfatea des VtHütipi-iignrtl * A waden to 0.6 mm, like this one in Fig. 1 shows the treated Sjopfeifofie and the applied epoxy layer

fabric that is classified according to one of the Va # äc & sfeeispiefe I to 3

rarter aef ITO ⁰ C 60 mm pressed on wmde, iänsichtOcii the high bandiese way eatsbeat a one-sided head encased 55 peratnr-fiaBfest ^ eä, the soldering machine is made and

a thickness of 0.6 nnn, the Sdreensmamrabaifceä with a one-sided knpi I d Fi 1 fki f di

i g p

How these wheels Fig. 1 is shown. Ia of Fig. 1 stranding! £ a layered material, which is applied to the

are a KüpfexfoBe i, eme pushes 2 in the same way as in igc example 1 with one

iingen after aod eme layer 3 aal iron already prepared pre-impregnation was provided, hoiKO Br. ^ i ^ jehalt vtH ^ sebea. 60 but with a core layer with little bromine content

VU-UU ^ OJ 9 aid the UbedSdheascBicht of the Vefaappresiats as

V **** ™ ****** «** harn Vogleicb ^ ei ^ iel 1 ansgebüdei warde. Which he-

Bn Lack C nrit eraem Bromgehaft voa 18 · / ·, befaatteoea are in the Nachsfeäienden day

drew the solids content of the lacfes, threw befle 1 znsarameffijBfalft.

died, in that 15 te

lBifalA ^ xkaiarzes and SS parts sdkSLfk & ägBsit der & rafedNfe bd 260 ° C at a

dte ^ poxy- iO0X25 ^^^ & ^ iKf i ⁰ )

qp ^ py ^^ p,

Sdme% mnkt 70 to SO ⁰ C) fofie in emer Bvate of l © ram m Läqgsncatang in

the center was removed by etching. Solder resistance is the time it takes to settle the copper foil lifts and comes off when a 100 X 100 mm test piece is on the surface a solder bath floats at 260 ° C, with the surface with the copper foil on the bottom. The resilience Against ignition is measured by removing the copper foil from a test specimen with a thickness of 12.7 mm and a length of 135 mm removed by etching and the test specimen

twice according to (US or Japanese standard) UL 94 is ignited, with the test piece perpendicular and the time until the flames go out is determined. For every layer material six specimens were used. The mean of the measurements and the measuring ranges (top and lowest value) are shown in Table 1. (Here is a mean of 5 s or less and a highest Value of 10 s or less prescribed by (US or Japanese standard) SE-O).

Table 1

High Solder- Resilience temperature- resistance against inflammation Adhesion Strength (g / cm) (lake) (lake) Comparative example 1 100 > 180 2.1 (0 to 6.5) Comparative example 2 95 > 180 2.8 (1.0 to 8.5) Comparative example 3 95 > 180 2.6 (0 to 7.5) Example according to the status of 20th 20th 2.0 (0 to 5.0) technology

Comparative example 4

In order to determine the influence of the bromine content in the surface part of the layer material connected with a copper foil on the adhesive strength, the following tests were carried out. Paints are made from bisphenol A epoxy resin and tetrabromobisphenol A epoxy resin as in Comparative Example 1, with the amount of tetrabromobisphenol A epoxy resin used being changed. The resulting paints were applied as a surface layer to prepreg A in Comparative Example 1 to produce corresponding prepregs. The relationship between the bromine content of the resin content in the surface layer and the high-temperature adhesive strength of the layer material for a copper foil is shown in FIG. 2 shown. If the bromine content in the surface layer exceeds 10 * / ο, the high-temperature adhesive strength is greatly reduced. Since an adhesive strength of more than approximately 50 g / cm is required for reliable adhesion between the copper foil and the layer material, the bromine content should generally be less than 10%.

Furthermore, the relationship between the bromine content of the entire layer material and the Resistance to ignition is shown in FIG. 3. As shown in FIG. 3, learned the flame extinguishing time does not meet the demands the quality SE-O the UL-94-Νοπη the resistance against inflammation, if the Bromgeaalt is less from 15 * / ·.

In the following further examples apply the ErSndang explained in which all parts are also rand percentages weight-related smd.

example 1

Two layer materials arasemerte on both sides with a thickness of the carrier material 11 of 0.6 mm and a resistance to inflammation corresponding to the good SE-O are produced, one side with a 35 μm thick copper foil and the other side with a 70 μm thick Copper foil is provided. An internal circuit 10 'with 30 ⁰ / o of an etched surface is formed on the respective side of the 70 μΐη thick copper foil 10 on both sides of the copper-clad laminated materials (Fi g. 4 A and AB). The copper surfaces of the above-described two-sided copper-clad laminate materials are at 30 ° C for 3 to g by dissolving 40 copper chloride and 500 ml of 37 ^e / cent hydrochloric acid then term in a l% aqueous solution of a min with an etching solution roughened to 1 1 is prepared, Aminosilane binder dipped and dried at 100 ° C for 30 min. Three layers 12 of prepreg B of Comparative Example 1 are placed between the inner layer copper foils 10 'of these double-sided laminated materials so that the layer of prepreg with a low bromine content can be in contact with the inner circuit surfaces. The entire arrangement is placed between two metal plates, which are held for 3 minutes under a pressure of 3 kg / cm ² in a press heated to 170 ° C. and then for 60 minutes under a pressure of 40 kg / cm ² in order to zn the layers together associate. The resulting multi-layer circuit board is then drilled, non-galvanically and electroplated with copper, medium: photo printing printed, plated with GoM and freed of the treasure or etching layers, which is carried out according to a process developed by be lens, as this is in the Figures 4D through 4H are shown; There is a through hole 13 there, a non-galvanically separated copper coating 14, an electroplated copper coating 15, a protective layer II, a gold coating 17 and an etched TeO (see window

Example 2

In the same way as in example 1 wild dB Inner layer folding surface be is the one used in Comparative Example 1

ίο

Paint B is then applied-copper foil surface inner-layer circuit on and dried for 10 min at 13O ⁰ C, is obtained μΐη whereby a ß-stage Beschichtuiigsfilm having a thickness of 30th Three layers of an already specified prepreg (bromine content 20%), in which there is no layer with a low halogen content in the surface layer, are then placed between these two layer materials, which are laminated on both sides, and treated in the same way as for the production of a multi-layer circuit board Example 1.

Example 3

A multilayer printed circuit board is treated as in Example 1 with the exception that three layers of the prepreg F of Comparative Example 3 are used.

Example 4

An approximately 25 μπι thick flat glass fabrics of 65/25 mm warps and 52/25-mm-shot is impregnated with the varnish D of Comparative Example 2 and at 130 ⁰ C for 10 min dried to obtain a prepreg G having a thickness of 30 μπι to produce. The resin content of this prepreg is 55%. The double-sided laminated layer materials of Example 1 are treated in the same way as in Example 1. Two layers of the prepreg G described above are applied to the respective inner layer circuits of the double-sided laminated layer materials. Three layers of an already specified prepreg (bromine content 20%) with a thickness of 130 μm are introduced between the prepreg G described above. The entire arrangement is treated in the same way as described in Example 1 for the production of a multilayer printed circuit board.

Example 5

Six layers of the prepreg F of Comparative Example 3 are placed between a 35 μm thick copper foil for lamination on both sides and a 70 μm thick copper foil for two-sided lamination. The entire arrangement is pressed for 60 minutes at 170 ° C. with a pressure of 40 kg / cm ^2.

In this way, two laminated materials are created on both sides. On the 70 μm thick copper foil side This double-sided laminated material is an inner layer circuit on the manufactured in the same way as in Example 1, from which

ίο a multilayer circuit board in the same way as in Example 1 is obtained.

Example 6

An approximately 35 μΐη thick flat glass fabric such as glass fabric of Example 4 is impregnated with the varnish B of Comparative Example 1 and is obtained dried for 10 min at 130 ⁰ C whereby a prepreg having a thickness H of 30 μΐη. Six layers of prepreg E of Comparative Example 3 are placed between the two layers of the above-mentioned prepreg and then placed between a 35 μm thick copper foil and a 70 μm thick copper foil for lamination on both sides. The entire arrangement is treated in the same way as in Example 5 in a press at 170 ^° C. in order to effect lamination on both sides. An inner-layer circuit is produced on this double-sided laminated material in the same way as in Example 1, and three layers of the prepreg F from Comparative Example 3 are introduced between the double-sided laminated material. The entire arrangement is treated in the same way as in Example 1 to produce a multilayer printed circuit board.

The multilayer printed circuit boards of Examples 1 to 6 are combined with an already developed multilayer printed circuit board in terms of solder resistance at 260 ° C and resistance to inflammation compared. The results are shown in Table 2:

Table 2 K Öt ™ litti * l- Wirlp ^ tanrUfaWkHt ι Pntflamimm » resistance
(lake) ** '· ■ ■' - "~ t
<sec) > 180
> 180
> 180
> 180
> 180
tend of technology 30 2.0 (0 to 5.0)
Ävo \ ι - »tit oüs ^ y.fcj
2.6 (I ^ Ms 5.8)
2.1 (0.8 to 5.2)
2 ^ (0.8 to 5.0)
3 ^ (1.0 to 8.0)
2.2 (0 to 6.0) example 1
Example 2
Example 3
Example 4
Example 5
Examples
Example according to S To do this, 3 sheets of drawing jfijiiiiMipn

Claims (5)

1 2 The number of printed circuit boards increased from _Claims : _{Janr m JaQr} ^ _the development of electronic 1 flame-retardant multilayer conductor facilities and devices. Printed circuit boards are now so widespread with two outer-layer metal circuits that essentially all of the electrical at least one inner-layer metal circuit, 5 niche devices and devices that are located between the outer-layer circuits use them With insulating layers from at least one part and devices the development of a multi-way hardened thermosetting brominated layer printed circuit board has been discussed, in order to enlarge its epoxy resin, whereby the circuits by means of the ever-packing density. For this reason, the few insulating layers that adhere to one another, so that the requirements placed on the properties of epoxy are characterized by the fact that at least prepregs Circuit used in, more and more strict; Lately touched, a bromine content of less than flame retardancy is also required. The previous 10 percent by weight and that the other 15 present invention uses an epoxy pre-impregnation part of the insulating layer such a bromine gnat for such a printed circuit board, which is held by the fact that the entire bromine content of the resin is flame retardant. zes total more than about 15 percent by weight To reduce the flammability of amounts to. Epoxy prepregs were previously halogen-containing 2. Multi-layer circuit board according to claim 1, ao term epoxy resins or halogen-containing hardeners used as a result characterized in that the thickness of the upper det. The flame retardancy decreases in this surface layer is about 10 to 50 μm. Fall with the halogen content too. With a circuit board 3. Multi-layer circuit board according to claim 1, however, has the use of such a halo- or 2, characterized in that the epoxy resin or hardener containing the gene is the large one Insulation to be connected to the inner layer circuit as a disadvantage that the adhesive strength for a circuit layer made of a prepreg made of a metal foil, such as a copper foil Thermosetting epoxy resin that is less high temperature (around 260 ° C) as well as its therals Contains 10 weight percent bromine. mixed resistance to the solder 4. Multi-layer printed circuit board after one of the ringers. Therefore the circuit claims 1 to 3, characterized in that 30 copper foil is slightly removed from the adhesive surface between it the surface part of the peel off on the surface of the and the insulating layer. The ones shown above shiny side of the inner layer circuit haf- Difficulties do not only affect the conductor ends Insulating layer from a prepreg with plates themselves, but also the electronic components ß-stage epoxy resin. parts that are provided on the printed circuit board. 5. A method for producing a difficult to develop 35 An electrolytic copper foil on metal-flammable multilayer printed circuit board according to a layered laminate has a glossy and one of claims 1 to 4, characterized in that it is matt. The matt side corresponds to the part of the layer materials that are drawn on both sides with a copper coating (10) which is produced with the base plate of the metal-covered layer materials (11) in contact that an inner layer circuit (10 ') on the 40, and has great roughness. The surface of one side of the respective layer material (11) of the matt side is treated in order to establish its adhesive strength so that several layers can be increased from as little as possible. A multilayer printed circuit board is produced at least one flame-retardant pre-impregnation by adhesive lamination of the glossy side of the gnat from a thermosetting epoxy resin on copper foil with a pre-impregnation. Which are brought, with at least one upper glossy side having a lower adhesive strength, however, area of the prepreg has a bromine content than the matt side. The shiny side of less than about 10 percent by weight and the part of the prepreg with the same roughness and surface should be subjected to such a treatment as the matt side, has a bromine content that the entire bromine, but at the same time the conductor track or must of the resin as a whole The surface treatment of the glossy impregnate with the low bromine content with the lower side should be limited to photoetching, and the inner layer circuit surface in contact with the Production of the printed multilayer conductor can stand, that the entire arrangement to the plate depends essentially on the adhesive strength of the layers and that 55 of the prepreg. On the one hand, the resulting multi-layer lei-bromine content of the prepreg must be increased, the plate drilled (13), non-electroplated copper plate so that the multilayer circuit board is more difficult to remove (14), electrolytically copper-plated (IS) and becomes flammable On the other hand, however, a high bromine content worsens the photographic print (16), a gold plating (17), the adhesive strength and the soldering and removal of the protective layer and etching agent resistance of the prepreg.
residues according to already developed It is an object of the present invention to subject a method. Multi-layer printed circuit board to indicate that not only is flame retardant, but also an excellent excellent adhesive strength and good solder resistance 65 has speed; furthermore, a process for the