DE102009025641A1 - Use of heat-activated adhesive tapes for the bonding of flexible printed circuit boards - Google Patents

Abstract

Use of a heat-activatable adhesive tape for the bonding of flexible printed circuit boards, wherein the adhesive tape comprises a layer of an adhesive comprising at least a) an acrylonitrile-butadiene copolymer, b) a novolak resin and c) a formaldehyde donor as a hardener.

Description

The The invention relates to a heat-activatable adhesive tape with low Fluidity at high temperatures and high Crosslinking speed for bonding flexible printed circuit boards, in particular for the production of electronic components.

flexible electronic circuit boards ("Flexible Printed Circuit Boards ", FPCBs; also as flexible printed circuit boards today) are used in a variety of electronic Devices like cell phones, radios, computers, printers and many others used. They are constructed of several with electrical Circuits provided (in particular etched) flexible copper-clad laminates (Flexible Copper Clad Laminates, FCCL; also referred to as copper-clad laminates) which together be glued. Also, FCCLs are commonly used in electronic Used devices. Flexible Copper Clad Laminates exist made of layers of copper and a high-melting, resistant Thermoplastics, mostly polyimide, more rarely polyester such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) or liquid crystalline Polymers (LCPs), and in part an adhesive layer in between.

to Production of the FPCBs or to reinforce the FCCLs with Reinforcement materials, so-called Stiffenern be often adhesive tapes with particularly high demands used. For one thing, to manufacture the Flexible Copper Clad Laminates (FCCLs) glued the copper foils to the polyimide films, usually By acrylate adhesives is effected, on the other hand are also individual FCCLs of the FPCBs are glued together, in this case mostly an adhesion of polyimide to polyimide or polyimide to copper instead of. In addition, the FCCLs or finished FPCBs are also on others Substrates (stiffening materials, so-called "stiffeners") glued to the partial stiffening of the laminates. As reinforcing materials be z. Rigid glass fiber epoxy (FR-4), polyimide, polyester, Steel and aluminum used. This is especially for example then of interest, if the flexible circuit board with electronic components as chips or the like to be provided and / or for the use is to be stabilized.

At the adhesive tapes used for these bonds will be made very high standards. Because very high Bonding performance, heat and media resistance achieved generally become heat-activatable Adhesive tapes used, which processes at high temperatures become. These tapes are allowed during This high temperature stress in the bonding of the FPCBs, often at temperatures around 180 ° C, no volatile Deliver ingredients. To achieve high cohesion, Should the tapes during this temperature load network. For a good wetting high pressures used during the bonding process, the bonding usually takes place with hot presses. It is necessary that the tapes at high temperatures only a small Have flowability so as not to get out of the glue joint to be squeezed out. This is due to high viscosity of the uncrosslinked adhesive tape or by rapid cross-linking reached. In addition, the tapes must then be solder bath resistant, that is, for a very short time a very high temperature load, such as of 288 ° C, survive. This allowed in the glued component no bubbles.

Out For this reason, the use of pure thermoplastics does not make sense although these melt very easily and for good Wetting the substrates to be bonded and provide a very fast bonding within a few seconds. On the other hand, they are so soft at high temperatures that they when glued under pressure, tend to swell out of the glued joint. This is also no Lötbadbeständigkeit given.

Usually are used for crosslinkable adhesive tapes epoxy resins or phenolic resins used with certain hardeners react to polymeric networks.

adhesives based on elastomers and epoxy resins often react quite slowly, so that the bonding process takes a long time and the Costs are driven upwards. To get around this, will be added different accelerators, which is the reaction of crosslinking run much faster.

adversely Here it is that the epoxy-crosslinked adhesive tapes, in particular the accelerated systems, even at room temperature or light begin to crosslink elevated temperatures.

Especially when high reaction rates are set to the Shortening processing times is the shelf life often humiliated. Most commercial products for This application must therefore be stored at 5 ° C be stored for a sufficiently long time to be able to.

The Phenolic resins can be divided into two groups, one the Resole, in the production of an excess of formaldehyde emerge, and on the other hand, the novolak, which at a Formaldehydunterschuss be formed.

The Resoles crosslink spontaneously in the heat or by acid addition with itself while releasing water while the novolaks only react with each other if a formaldehyde splitter as a crosslinker acts. In their networking, no water is split off.

Usually is dispensed with the use of phenolic resins, if a bubble-free Process is desired. For one, the water leaves which split off the resoles in the reaction, a generation of bubbles On the other hand, the use of novolaks is a crosslinker necessary, in the reaction at least formaldehyde, often, as in the case of hexamethylenetetramine, can also split off ammonia. These two gaseous substances can also lead to blistering.

The Crosslinking resins are mainly used in construction bonding used and give very brittle after curing Adhesives that achieve high bond strengths, but hardly are flexible.

A Increasing flexibility is for use in flexible circuit boards inevitable. For one thing The bonding can be done with the help of an adhesive tape, ideally wound on a roll, on the other hand, it is flexible PCB, which must be bent, to recognize well the example of printed circuit boards in a laptop, in which the hinged Screen connected via FPCBs to the other circuits is.

A Flexibilization of this reaction resin adhesive is possible in two ways. On the one hand, elastomeric chains have flexibilized epoxy resins, but due to the very short elastomer chains only a limited flexibility Experienced. The other option is flexibility through the addition of elastomers to reach that of the adhesive be added. Since these elastomers are not cross-linked chemically, Only elastomers can be used, which in high temperatures still have a high viscosity, since the adhesive otherwise squeezed out during pressing from the bondline becomes.

There the adhesive tapes are mostly made from solution it is often difficult to find elastomers, long-chain enough not to flow at high temperatures, on the other hand, but still in conventional solvents are soluble or dispersible.

A Production via a hotmelt process is at networking Systems are very difficult, as early Networking can be avoided during the manufacturing process got to.

Especially suitable here is the use of nitrile rubbers in certain Solvents are soluble, or by a Kneading process transferred into a spreadable suspension can be, but also limited at high temperatures flow.

Adhesive tapes of nitrile rubbers and phenolic resins are z. B. from the DE 44 27 802 A known. These tapes are used for the bonding of chip modules in smart cards.

Adhesive tapes for Smard Cards are also in the EP 1 615 978 A described. Here are also called novolak resins. The application of the bonding of chip modules in smart cards, however, makes completely different demands on the adhesive tapes than the bonding of flexible printed circuit boards. So the smart cards do not have to pass a solder bath test, moreover, a few bubbles in the bond no problem, as long as they do not affect the adhesive performance, since they are not visible. A transfer of the doctrine of EP 1 615 978 A Therefore, adhesion to flexible printed circuit boards is not obvious.

task The invention thus provides an adhesive tape for bonding of flexible printed circuit boards or for bonding to provide the production of flexible printed circuit boards, through whose Use the disadvantages of the prior art entirely or at least partly avoided.

Preferably, the squeezing of the adhesive film from the bondline during hot pressing should be minimized. In addition, it should advantageously not come to blistering during the hot pressing or the subsequent processes, more advantageously, a shelf life should be guaranteed over 1 year at room temperature. In spite of the long shelf life, the fastest possible reaction is desired in order to obtain the Accelerate processes.

Solved This task is accomplished by the use of an adhesive tape, as is is characterized in detail in the main claim. object the dependent claims are advantageous developments of the subject invention and a by the use available Adhesive bond.

• a. mindestens einem Acrylnitril-Butadien-Copolymeren,
• b. mindestens einem Novolakharz, und
• c. einem Formaldehydspender als Härter.

Accordingly, the invention relates to the use of a heat-activatable adhesive tape for the bonding of electronic components and printed circuit boards, comprising an adhesive consisting of at least

• a. at least one acrylonitrile-butadiene copolymer,
• b. at least one novolak resin, and
• c. a formaldehyde donor as a hardener.

The Amount ratio of acrylonitrile-butadiene copolymers to the novolak resins is advantageously in the range of 3: 7 to 8: 2, so that preferably the acrylonitrile-butadiene copolymers with a Weight fraction of 30 to 80 wt .-% and the novolak resins with a Weight fraction of 20 to 70 wt .-% are present, wherein the components a. and b. add to 100 wt .-%.

The Novolak resin is in particular capable of doing so at high temperatures to chemically crosslink with the help of the hardener. The networking takes place according to the present invention in particular solely by chemical reaction of the novolak resins with the hardeners in the heat and / or by reaction of the hardener with the novolak resins and the polymer matrix in the heat.

Under heat-activatable adhesive accordingly becomes a polymer composition understood, which is crosslinked upon introduction of thermal energy and at the same time a bond strength sufficient for the bonding (sufficient adhesion, sufficient cohesion) builds. The polymer composition can not be weak at room temperature or also be strong touch sticky (tacky, tacky).

The Activation temperatures for thermal crosslinking are well above room temperature, usually at least 100 ° C or more. Preferred activation temperatures for thermal crosslinking, in particular the required Bonding strength to guarantee at least 120 ° C, in particular between 140 ° C and 220 ° C.

The for the adhesive tape used in the invention Adhesive used may affect the aforementioned components a. to c. restrict, but if necessary, more Contain ingredients.

Of the general term "adhesive tape" includes the meaning this invention all planar structures as in two dimensions extended films or film sections, tapes with extended Length and limited width, band sections, die cuts and the same.

Ideally are the novolak resins and hardeners (formaldehyde donors) in a ratio of 50: 1 to 5: 1 wt .-% (novolak resins: Hardener), preferably 20: 1 to 7: 1 wt .-%, used.

Surprisingly It has been shown that, despite being used for novolac resins too Expected Abspaltprodukte such as formaldehyde or Ammonia (see above) is not visible when using novolacs Bubble formation in the glued joint gives.

It has shown that the invention used Adhesive is heat-activated, cross-linked in the heat and in the Heat well on the substrate to be bonded, a shows good adhesion to polyimide, temporarily stable to temperature at least 288 ° C and is soluble in the uncrosslinked state or suspendable in organic solvents.

The Adhesive used according to the invention is suitable Therefore, it is excellent for solving the above mentioned problem.

Acrylonitrile-butadiene copolymers, in the context of this document also referred to as acrylonitrile-butadiene rubbers, nitrile-butadiene rubbers or, for short, as nitrile rubbers, may in particular be used according to the invention in particular all acrylonitrile-butadiene rubbers having an acrylonitrile content of 15 to 55% by weight. Likewise, copolymers of acrylonitrile-butadiene and isoprene can be used. The proportion of 1,2-linked butadiene is variable. The aforementioned polymers can be hydrogenated to a different degree be; Fully hydrogenated polymers with a double bond content of less than 1% can also be used.

nitrile-butadiene rubbers are polymerized either hot or cold.

Commercially, such systems are available, for example, under the names Europrene ^™ from Eni Chem, Krynac ^™ and Perbunan ^™ from Bayer or Nipol and Breon from Zeon; hydrogenated systems are available under the name Zetpol from Zeon or Therban commercially available from Lanxess in varying degrees. The abovementioned products are examples of systems which can be used advantageously according to the invention.

It shows that the nitrile rubbers with higher acrylonitrile give better adhesion. Also beneficial for a strong bond is a high molecular weight, taking care of it care must be taken that the polymer is still in solution or Suspension can be brought.

The Nitrile rubbers can be dissolved in short-chain alcohols and ketones as ethanol or butanone solve or suspend. there Butanone is preferred because the remaining components, especially the novolak resins, better dissolve in butanone.

novolaks are soluble, meltable, not self-hardening and storage stable phenolic resins. They are made by condensation of Formaldehyde and excess phenol in the presence usually made of acidic catalysts.

Your Crosslinking to thermoset molded parts is achieved with the aid of a hardener, the formaldehyde splits off, z. Hexamethylenetetramine (urotropin), carried out.

These Crosslinking is faster because of steric hindrance in para- as in ortho position. Therefore, for one especially fast crosslinking prefers novolac resins, which are in ortho position containing linked phenol units used.

Examples for advantageously usable according to the invention Novolak resins are z. For example the products Durez from Sumitomo Bakelite and / or the Plenco products of the Plastics Engineering Company.

When Hardeners are different formaldehyde donors in question such as As hexmethylenetetramine (hexa, HMTA, urotropin) and / or different Methylolamine derivatives such as trimethylolmelamine or hexamethylolmelamine.

By the chemical crosslinking of the hardener with the novolak resins become very strong within the adhesive film reached. But also the bond strengths to the polyimide are very high.

Around to increase the adhesion is also the addition of Adhesive resins compatible with the elastomers ("tackifiers") possible in an advantageous manner.

Suitable tackifiers in the heat-activatable adhesives according to the invention are, for example, nonhydrogenated, partially or fully hydrogenated rosin-based rosin derivatives, hydrogenated polymers of dicyclopentadiene, non-hydrogenated, partially, selectively or completely hydrogenated hydrocarbon resins based on C ₅ , C ₅ C ₉ or C ₉ monomer streams, polyterpene resins based on α-pinene and / or β-pinene and / or δ-limonene, hydrogenated polymers of preferably pure C ₈ and C ₉ aromatics are used. The aforementioned adhesive resins can be used both alone and in admixture. Tackifiers may advantageously be added up to 20% by weight, based on the blended adhesive.

It Even small amounts of epoxy resins can be used. To maintain storage stability, the amount should be Epoxy resin preferably does not exceed 10% by weight.

When Epoxy resins become both monomeric and oligomeric compounds understood with more than one epoxide group per molecule. These may be reaction products of glycidic esters or epichlorohydrin with Bisphenol A or bisphenol F or mixtures of these two. It is also possible to use epoxy novolac resins obtained by reaction of epichlorohydrin with the reaction product of phenols and formaldehyde.

Also monomeric compounds with multiple Epoxidendgruppen, as diluents are used for epoxy resins, are usable. Also are elastically modified epoxy resins used.

Examples of advantageous epoxy resins are Araldite ^™ 6010, CY-281 ^™ ECN ^™ 1273, ECN ^™ 1280, MY 720, RD-2 from Ciba Geigy, DER ^™ 331, 732, 736, DEN ^™ 432 from Dow Chemicals, Epon ^™ 812 , 825, 826, 828, 830 etc. from Shell Chemicals, HPT ^™ 1071, 1079 also from Shell Chemicals, Bakelite ^™ EPR 161, 166, 172, 191, 194 etc. from Bakelite AG.

Advantageous usable commercial aliphatic epoxy resins are, for example Vinylcyclohexane dioxides such as ERL-4206, 4221, 4201, 4289 or 0400 of Union Carbide Corp.

Advantageous usable elasticized epoxy resins are available from the company Noveon under the name Hycar.

Advantageously usable Epoxidverdünner, monomeric compounds with multiple epoxy groups are for example Bakelite ^TM EPD KR, EPD Z8, EPD HD, EPD WF, etc. Bakelite AG or Polypox ^TM R9, R12, R15, R19, R20, etc. of the company UCCP.

• – primäre Antioxidanzien wie zum Beispiel sterisch gehinderte Phenole
• – sekundäre Antioxidanzien wie zum Beispiel Phosphite oder Thioether
• – weitere Alterungsschutzmittel wie sterisch gehinderte Amine
• – Prozessstabilisatoren wie zum Beispiel C-Radikalfänger
• – Lichtschutzmittel wie zum Beispiel UV-Absorber
• – Verarbeitungshilfsmittel
• – Füllstoffe, wie zum Beispiel Siliziumdioxid, Glas (gemahlen oder in Form von Kugeln), Aluminiumoxide, Zinkoxide, Titandioxide, Ruße, Metallpulver, etc.
• – Farbpigmente und Farbstoffe sowie optische Aufheller
• – gegebenenfalls weitere Polymere von bevorzugt elastomerer Natur.

As further additives can be optionally used:

• Primary antioxidants such as sterically hindered phenols
• - secondary antioxidants such as phosphites or thioethers
• - Other anti-aging agents such as sterically hindered amines
• - Process stabilizers such as C radical scavenger
• - Sunscreens such as UV absorbers
• - processing aids
• Fillers, such as, for example, silica, glass (ground or in the form of spheres), aluminum oxides, zinc oxides, titanium dioxides, carbon blacks, metal powders, etc.
• - Color pigments and dyes as well as optical brighteners
• Optionally further polymers of preferably elastomeric nature.

The aforementioned and possibly further additives may be alone or especially when used in combination with each other, if by adding them the properties of the adhesive in terms of to be adjusted to specific uses.

By The use of plasticizers can increase the elasticity of the crosslinked Adhesive mass be increased. As a plasticizer can while, for example, low molecular weight polyisoprenes, polybutadienes, Polyisobutylenes or polyethylene glycols and polypropylene glycols be used.

There the nitrile rubber is not too low even at high temperatures Viscosity, it comes during the gluing and hot pressing not to the exit of the adhesive from the Bonded joint. During this process, the novolak resins crosslink and optionally the polymer matrix with the hardeners, it results a three-dimensional network.

to Production of the adhesive tape become the constituents of the adhesive especially in a suitable solvent, for example Butanone, dissolved or suspended, on a flexible substrate, that with a release layer (for example, a release paper or a release film), coated and dried, so that the mass of the substrate can be easily removed again. To appropriate packaging can punched, rolls or other moldings produced at room temperature become. Corresponding shaped bodies are then preferably at elevated temperature to the substrate to be bonded, for example polyimide, glued on.

It is also possible, the adhesive directly onto a polyimide to coat. Such adhesive films can then in particular used to cover copper tracks for FPCBs become.

For the insert can be used according to the invention Adhesive tapes for better handling with a cover material (Release liners, liners), for example with siliconized paper, siliconized polymer film (such as siliconized PET film) or like.

It is not necessary that the bonding is carried out as a one-step process, but on one of the two substrates, the tape can first be stapled by lami in the (moderate) heat ned. In the actual hot-bonding process with the second substrate, the novolak resins then cure completely or partially and the adhesive film achieves the high bond strength.

The Novolak resins and the hardener should preferably be used in the Laminating temperature is still no chemical reaction, but only react with each other when hot-melted.

The Adhesive tapes according to the invention show in the so-called quick press processing method (QPP; Technology: hot pressing, for example, for 2 minutes, 180 C, 15 bar; subsequent furnace storage, for example 30 minutes to 1 hour at 150 ° C) and in the Heatpress process (HP, hot pressing for example 30 min at 180 ° C, 15 bar) significant advantages, by at least equal quality bonding products at significantly improved conditions (shorter process times) can be achieved, so can in Quickpressprocessing method for comparable results on the subsequent furnace storage step be dispensed with or alternatively the pressing time in the hot pressing step reduced to 1 min (with remaining subsequent furnace storage) become; in the Heatpress process can for comparable results the hot pressing step is also reduced to one minute (while maintaining the remaining parameters on the example values given above).

With leave the tapes shown in this document excellently etched and / or not etched gluing flexible printed circuit boards together (whereby both a Bonding of polyimide on polyimide or also a bond on Polyimide can be made on copper; It can have two printed circuit boards can be glued together, it can also be more than two Printed circuit boards are glued together and thus a multi-circuit board composite getting produced); furthermore, can be excellently etched and / or not yet etched flexible printed circuit boards or partially on reinforcing materials (stiffeners) stick or partially with reinforcing materials (Stiffener) are glued (in particular a bond Of polyimide on the Stiffener material, but also a bond the copper layer can be made on the Stiffener material).

The Bonding takes place in particular in the hot-pressing process, preferred by Quickpressprocessing and / or Heatpress-Processing (see above).

object The invention is therefore further an adhesive composite of at least two bonded flexible printed circuit boards with an inventively described Duct tape; in particular with a heat-activatable adhesive tape, as it is for use according to any of the claims is described; further glued in particular as shown above. The invention further provides an adhesive composite of at least a flexible printed circuit board or an adhesive composite of at least two flexible circuit boards on a reinforcing material with an adhesive tape described according to the invention, as it is for use according to any of the claims is described; further glued in particular as shown above.

Examples

in the The invention will be more closely understood by a few examples described, without limiting the invention in any way.

example 1

100 Parts Breon N41H80 (nitrile rubber from Zeon with 41% acrylonitrile) and 100 parts of Durez 12687 (Novolak resin from Sumitomo-Bakelite, already contains 7.4% hexamethylenetetramine) were used as a 30% suspension prepared in butanone in a kneader. The kneading time was 20 H. The heat-activatable mass then became solution coated on a siliconized PET film ("liner") and dried at 100 ° C, leaving a 25 μm thick Adhesive layer was created.

Example 2

It was an adhesive according to the same procedure as in Example 1 prepared with the composition 100 parts Breon N41H80, 50 Parts (based on solid substance) of the resin Durez 37087 (a 55% strength Solution of Durez 12687 in butanone without hardener) and 7 parts hexamethylenetetramine.

Example 3

Instead of the nitrile rubber in Example 1, a hydrogenated nitrile rubber Therban 4369 (partially hyd nitrated rubber with 43% acrylonitrile) from Lanxess.

Comparative Example V4

It An adhesive was prepared as in Example 1, in which the Half of the novolak resin by the Resolharz 9610 LW Fa. Bakelite was exchanged.

Comparative Example V5

It the same raw materials were used as in Example 1, however To 100 parts of the nitrile rubber were added 300 parts of the novolak resin added.

Comparative Examples V6, V7 and V8

As further comparative examples, three commercial products were used for the described application. V6: Sony 3410 from Sony (Nitrile rubber (70% butadiene / 30% acrylonitrile) epoxy resin composition, 1: 1, on liner) V7: Sony 3450 from Sony (Poly-n-butyl acrylate, polyacrylonitrile, polyethyl acrylate, epoxy, 2: 1: 4: 2, on liner) V8: Pyralux LF 100 from DuPont (modified acrylate adhesive on liner; elastomer component: 82% n-butyl acrylate, 12% acrylonitrile, 6% acrylic acid; resin component: phenol-formaldehyde resin (novolak))

Bonding of FCCLs with the produced adhesive tape

A FCCL (Flexible Copper Clad Laminate) Pyralux LF9110R [sequence of layers (Cu 305 g / m ²⁾ + (25 microns acrylate adhesive) + (25 microns Poliimidschicht; Kapton ^®) is respectively connected to the produced according to Examples 1 to V5 tapes onto a reinforcing plate glued from FR-4 ("Stiffener", about 10 cm x 2.5 cm).

To the adhesive tape is applied to the polyimide film of the polyimide / copper foil FCCL laminate laminated at 100 ° C and the liner removed, the Adhesive strips slightly shorter than the FCCL to be bonded is to have a handle later. Subsequently This composite of FCCL and adhesive tape on the Stiffener FR-4 laminated at 100 ° C, and the whole composite in one heatable office glue press at 180 ° C at one pressure of 1.3 MPa for 20 min pressed ("hot pressing").

For the recording of the reaction curve was the pressing time of 1 min to Varies for 30 minutes.

Test Methods

The Properties of the prepared according to the above examples Adhesive films are examined by the following test methods.

L-Peel test with FCCL-Stiffener composite [IPC-TM-650 No. 2.4.9]

With a tensile testing machine from Zwick is in the after FCCL composites made according to the method described above and FR-4 Stiffener and the commercially available Comparative Examples V6 to V8 the FCCL at 90 ° angles subtracted from the Stiffener at a speed of 50 mm / min and the required force measured in N / cm. For the Prepared Examples and Comparative Examples 1 to 3 and V4, V5, the measurements are made immediately after bonding at 23 ° C and 50% rel. Humidity carried out. Every reading becomes determined in triplicate.

response curves

With Examples 1 and 2 and Comparative Examples V6, V7 and V8 reaction curves were recorded, but this was the bond strength in the L-peel test as described above depending on Pressing time (hot pressing on the Stiffener) measured. At the same time, the bubble pattern was judged after the solder bath test.

Ausquetschverhalten

The Squeezing behavior was determined as follows. The Adhesive tape was as described above at 100 ° C on the Laminated FCCL and removed the liner. Subsequently were 3 holes of 5 mm diameter punched into the composite. This perforated composite was again laminated to the FR-4 material and then pressed (hot pressing, heated Bürklepresse at 180 ° C at a pressure of 4 MPa for 20 minutes). After a pressing time of 20 minutes, it was measured how far the adhesive was squeezed into the holes. It was the average of the maximum range in the determined individual holes.

solder bath

The FCCL-Stiffener composites bonded according to the procedure described above will be for 10 seconds with the FCCL side to a 288 ° C laid hot solder bath. The bonding is called solder bath resistant, if no bubbles in the adhesive joint, which inflate the polyimide film of the FCCL or simply be detected optically. Of the Test is considered failed, if already a slight Blistering occurs.

storage stability

Of the Test is considered passed if under the given storage conditions no significant after storage of the roll of adhesive film Waste of bond strength against an adhesive film Immediately after production is determined (measurement L-Peel test with FCCL-Stiffener composite as shown above).

Results:

L-peel test

For the adhesive assessment of the above examples, first the L-Peel test was performed. Table 1: L-peel test example 1 2 3 V4 V5 L-peel test in N / cm 32.7 34.1 22.6 29.8 18.2

The Example V5 did not fare well because of its stiffness laminate and wet the surface of the bonding partners only insufficient, which is why it leads to lower bond strengths came.

solder bath

Of the Solder bath test was conducted with Examples 1 to 3 and Comparative Examples V4 and V5 performed. He was of the examples 1, 2 and 3 passed, the two comparative examples showed against it a series of bubbles in the glued joint, so the test failed has been.

Temporal behavior / reaction curves

The results of the "reaction curves" test are shown in Table 2. Table 2: Reaction rate, bond strength as a function of the press time. Data: [N / cm] // Bubble pattern (for every 5 minutes, there were no more bubbles in any of the examples) pressing time example 1 Example 2 Example V6 Example V7 Example V8 1 min 28 // kB 27 // kB 18 // kB 28 // B 2.7 // WMB 2 min 29 // kB 28 // kB 18 // kB 29 // WMB 3.9 // WMB 5 min 29 28 19 30 6.4 10 min 29 28 23 30 15 30 min 30 29 25 30 19

• kB: keine Blasen; wMB: wenige Mikroblasen; B: Blasen

In this mean:

• kB: no bubbles; wMB: few microbubbles; B: bubbles

in the Comparison of Examples 1 and 2 with the commercial products shows that Examples 1 and 2 react much faster as Comparative Examples V6 and V8 and significantly fewer bubbles even after short injection times generate as V7.

Ausquetschverhalten

The results of the "squeezing behavior" test are shown in Table 3. Table 3: Ausquetschverhalten example 1 Example 2 Example V6 Example V7 Example V8 Squeezing in mm 0.4 0.5 0.5 1.3 0.8

The Examples V7 and V8 show a much stronger squeezing as the inventive examples 1 and 2.

storage stability

The Results of the L-peel test of the invention Examples after a storage period of one year at room temperature (25 ° C) and ambient humidity remained at the level of in Table 1, while Comparative Examples V6 and V7 after the same storage a drop in the force / displacement value by 70% -90% in the L-Peel test.

The Examples V6 and V7 must be stored at 5 ° C, to almost maintain their properties while examples 1 and 2 stable for at least 1 year at room temperature are.

conclusion

The Comparative Examples V4 and V5 show no sufficient resistance in the Lötbadtest. Comparative Example V5 leaves Moreover, they do not laminate sufficiently well. The comparative examples V6 and V8 react very slowly in the sense of the crosslinking reaction between novolak resin and hardener, while the Comparative Example V7 when compressed to an intolerable Blistering tends. Examples V6 and V7 are also not included Room temperature storable.

Just Inventive examples 1, 2 and 3 are made all exams.

The Adhesive tapes described in this document are excellent suitable for the use according to the invention, and in particular the object according to the invention to fulfill. The special feature of the invention Adhesives is the balance of products.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4427802 A [0019]
• - EP 1615978 A [0020, 0020]

Claims (12)

Use of a heat-activatable adhesive tape for the bonding of flexible printed circuit boards, wherein the Adhesive tape comprising a layer of an adhesive at least a) an acrylonitrile-butadiene copolymer, b) a novolak resin and c) a formaldehyde donor as a hardener, having. Use of a heat-activated adhesive tape after Claim 1, characterized gekennzeichet that the quantitative ratio of acrylonitrile-butadiene copolymers to novolak resins in the range from 3: 7 to 8: 2. Use of a heat-activated adhesive tape after at least one of the preceding claims, characterized that the proportion of novolak resins to the hardener (Formaldehyde donor) in the range of 50: 1 to 5: 1 wt .-%, preferably in the range of 20: 1 to 7: 1 wt .-%, is. Use of a heat-activated adhesive tape after at least one of claims 1 to 3, characterized in that that the acrylonitrile content in the acrylonitrile-butadiene copolymer 15 to 55 wt .-% is. Use of a heat-activated adhesive tape after at least one of the preceding claims, characterized that the acrylonitrile-butadiene copolymer at least partially hydrogenated is. Use of a heat-activated adhesive tape after at least one of the preceding claims, characterized the formaldehyde donor is hexamethylenetetramine. Use of a heat-activated adhesive tape after at least one of the preceding claims, characterized that the adhesive tape in addition an epoxy resin with maximum 10 wt .-% in the mixture. Use of a heat-activated adhesive tape after at least one of the preceding claims, characterized that the adhesive tape comprises tackifying resins, accelerators, dyes, Soot and / or metal powder contains. Use of a heat-activated adhesive tape after at least one of the preceding claims, characterized that the tape at temperatures above 150 ° C crosslinked; in particular by reaction of the novolak resins with the Formaldehyde donors. Use of a heat-activatable adhesive tape according to one of the preceding claims, characterized the adhesive contains further elastomers. Adhesive composite of at least two glued flexible Printed circuit boards, wherein for the gluing of printed circuit boards together a heat-activatable adhesive tape according to a of the preceding claims. Adhesive composite of at least one flexible printed circuit board and a reinforcing material, wherein for the Gluing the PCB with the reinforcing material a heat-activatable adhesive tape according to any one of Claims 1 to 10 is used.