Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-07-20
2001-03-13
Ball, Michael W. (Department: 1783)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S275700, C156S330000
Reexamination Certificate
active
06200408
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the adhering of a component, such as an electronic, electric or optical component to a surface using an adhesive or a cement. More specifically, the present invention relates to a method for bonding a component to a surface using an epoxy-based cement or adhesive made in accordance with the present invention.
In many technical fields, workpieces are already being connected and fastened exclusively by cementing. Conventional fastening methods such as soldering, welding, screwing or the like are thus being supplanted by cement or adhesives. For the constantly expanding fields of use, cements are needed which must satisfy a wide variety of requirements. In electronics and optical communications technology, reactive resins are being increasingly used for reliable and cost-effective assembly of different materials reasons of production technology, one-component systems are desirable, it being possible to employ these for bonding directly, without additional preprocessing. However, it is disadvantageous here that the one-component systems can only be rapidly hardened at increased temperatures. Short cycle times which as are necessary for an automatic production are thus difficult to achieve.
For different cementing problems, particularly in optical communications technology, a precise aligning of the components to be cemented is required. This must occur prior to the final hardening, whereby it is often necessary to fix the aligned components until hardening since the cement passes through a low-viscosity state during hardening. In addition, the cement can comprise a shrinking behavior, which in turn results in a misalignment.
Besides the de-aligning, the thermal load exhibited during the hardening of one-component reactive resins can lead to strong tensions or even to damage to the parts, or respectively, components to be cemented. In addition, the temperature sensitivity of parts that are to be cemented can limit the hardening temperature, thus necessitating cements that harden at lower temperatures.
One possibility for rapid fixing is offered by UV-hardenable cements. However, in many cases these do not comprise the necessary combination of properties that leads to a lasting, and reliable bond. Thus, in many cases a second bonding agent is employed, usually an epoxy resin, in order to guarantee the reliability and permanence of the cemented connection. This has the disadvantage that light-hardening resin and epoxy resin can be disadvantageously influenced. Furthermore, the mere need for two different bonding agents is undesirable in and of itself.
German Patent Application No. 40 38 989 teaches a bonding method with the aid of a cationically initiated hardenable epoxy resin wherein the cement is activated with the aid of UV light and can then be hardened thermally at a relatively mild temperature. It is disadvantageous in this method that a heating of the cemented location must occur for rapid fixing, and the transfer of a sufficient amount of heat is necessary. This limits the cycle times in automatic production methods. In addition, this cement hardens only where an illumination occurs, not at points where an illumination does not occur at all.
Another problem is to find a cement that is suitable for thermoplastic surfaces which enables a rapid and exact hardening.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide a method for the rapid and exact cementing of two joint parts, at least one of which can comprise a thermoplastic surface.
These and other objects are achieved by a method in accordance with the present invention which comprises the steps of depositing a cement in a seam disposed between the component and the surface to which the component is to be bonded to, joining the surfaces to be bonded, aligning the component with the surface, fixing the component to the surface by UV/VIS illumination, and, heating the component and surface to thermally harden the cemented location.
In an embodiment, the method of the present invention comprises the steps of filling a seam disposed between the component and the surface with a cement to produce a cemented location, the cement comprising an epoxy-based cement comprising from about 20 to about 70 percent by weight of a cationically hardenable solvent-free epoxy comprising a conversion product of a cycloaliphatic diepoxy and an aromatic compound that comprises OH-groups, from about 10 to about 60 percent by weight of a compound comprising multiple hydroxyl groups, from about 0.02 to about 2 percent by weight of a cationic photoinitiator, from about 0.02 to about 2 percent by weight of a latent thermal initiator comprising a thiolanium salt, and from about 20 to 60 percent by volume of a filler with a maximum particle size of 50 &mgr;m, and wherein the cemented location comprises a thermoplastic surface, aligning the component on the surface, irradiating the cement with electromagnetic radiation in the UV/VIS region thereby fixing the cemented location, heating the cemented location to thermally harden the cemented location.
In an embodiment, the irradiation of the cement occurs over a time period ranging from about 0.1 to about 10 seconds.
In an embodiment, the component comprises a metallic or a metallized surface that faces the seam.
In an embodiment, the seam has a thickness ranging from about 20 to about 200 &mgr;m.
In an embodiment, the filler comprises an inorganic filler.
In an embodiment, the filler comprises a mineral filler.
In an embodiment, the cement is applied to the component.
In an embodiment, the cement is applied to the surface.
In an embodiment, the component is selected from the group consisting of an electrical component, an electronic component and an optical component and the method is carried out within a cycle time ranging from about 0.1 to about 10 seconds.
A cement on an epoxy base is used which is modified with polyol and which contains initiators for both light-induced cationic hardening and for thermal hardening. Surprisingly, it has been demonstrated that with this type of cement a rapid and sufficiently reliable fixing of the cemented location is possible by means of UV illumination with a UV lamp, for example. The fixing, occurs within a maximum time of 15 seconds and can be achieved in a 5-second irradiation period already in an exemplifying embodiment. It is still possible to achieve significantly shorter illumination times with a UV laser. By means of the cationic catalyzer, it is sufficient to illuminate only a proportionally small surface of the cement, or respectively, of the cemented location and still to achieve a sufficient fixing of the overall cemented connection.
The complete hardening can occur in a later tempering step at relatively moderate temperatures of 130 to 150° C., for example. It is thus possible first to fix several cemented locations simultaneously or successively and then to thermally harden the cemented locations jointly. Several cemented locations can thus be situated on a common substrate.
Surprisingly, it has also been demonstrated that, with the inventive method, sufficiently fast cemented connections can be produced between components, at least one of which comprises a thermoplastic surface. For such cementing problems there were previously no known satisfactory solutions based on UV-hardenable epoxy resins.
Particularly good cemented connections are obtained between thermoplastic surfaces and metallic or metallized surfaces. Gold-plated parts of electronic components which are to be connected to precise injection-molded parts made of thermoplastic can serve as an example here.
For a particularly low-shrinkage cemented location with a low thermal coefficient of expansion, a cement is used which contains an inorganic or mineral filler in a proportion of 20 to 60 percent by volume.
Fillers are preferably on a silicic acid base, such as quartz meal or quartz ware meal. Extra-fines with a maximum particle diameters of 10 to 50 &mgr;m are preferably used, these enabling
Bayer Heiner
Wipfelder Ernst
Ball Michael W.
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
Tolin Michael A.
LandOfFree
Method for cementing a component to a surface does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for cementing a component to a surface, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for cementing a component to a surface will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2449083