Patent Application
20140071595
The described embodiments relate generally to bonding substrates together and more particularly to forming a bond between two substrates using laser ablation on one or more bond surfaces disposed on the substrates.
The bond strength of a bond between a first substrate and a second substrate bonded through an adhesive can be affected by many factors. First of all the affinity of the first substrate and the second substrate to a selected adhesive can affect the wetting of the bond area and thereby affect the resulting bond strength. Another factor can be the mechanical properties of the selected adhesive, such as an ultimate bond strength and sensitivity to strain rate. A third factor for bond strength can be in regards to mechanical properties of the bond interface area. For example, an ultimate strength of the substrate material and sensitivity to strain rate of substrate material in the bond area can be an important factor for bond strength.
In some cases, a product design may not have enough degrees of freedom to allow the designer enough choices to formulate a relatively strong bond between substrates. For example, a selected substrate may have a poor bonding characteristics with a particular adhesive. However, the may be no design flexibility in the choice of substrate material and, furthermore, the choices for an adhesive may be limited because required operating conditions, required tack or other adhesive working characteristics.
Therefore, what is desired is a way to bond substrates together that can produce relatively strong bonds while maintaining substrate choices.
This paper describes various embodiments that relate to bonding a first substrate to a second substrate including laser ablating at least one substrate.
One method for bonding a first substrate to a second substrate can include the steps of laser ablating a first bond surface of the first substrate, where the first bond surface is less than the entire first substrate, disposing an adhesive onto a first bond surface on the second substrate, where the first bond surface on the second substrate corresponds to the first bond surface on the first substrate, and bonding the second substrate to the first substrate by placing the adhesive in direct contact with the first bond surface of the first substrate.
In another embodiment, another method for bonding a first substrate to a second substrate can include the steps of laser ablating a first bond surface of the first substrate, where the first bond surface is less than the entire first substrate, of laser ablating a first bond surface of the second substrate, where the first bond surface is less than the entire second substrate, disposing an adhesive onto a first bond surface on the second substrate, where the first bond surface on the second substrate corresponds to the first bond surface on the first substrate, and positioning the adhesive to be in direct contact with the first bond surface of the first substrate.
In yet another embodiment, a housing can include a rear cover including at least one opening, where the rear cover is configured to contain electrical components for the portable electronic device and including a laser ablated bonding surface, a front cover, configured to be clear and fit into the at least one opening of the rear cover and configured to have a bonding surface matching the bonding surface of the rear cover, a display unit placed within the rear cover and positioned behind that front cover, and an adhesive applied on the first bonding surface of the rear cover.
A bonded assembly can include a first substrate with a laser ablated bonding surface less than the entire first substrate, a second substrate with a first bonding surface corresponding to the shape of the bonding surface of the laser ablated bonding surface and an adhesive layer disposed between the first bonding surface of the first substrate and the first bonding surface of the second substrate.
Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments.
The described embodiments and the advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings. These drawings in no way limit any changes in form and detail that may be made to the described embodiments by one skilled in the art without departing from the spirit and scope of the described embodiments.
Representative applications of methods and apparatus according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be taken as limiting.
In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting; such that other embodiments may be used, and changes may be made without departing from the spirit and scope of the described embodiments.
Often a bond between a first substrate and a second substrate can have a limited bond strength. The bond strength can be limited because of substrate choice and because of adhesive bonding characteristics between a selected adhesive and the first and/or the second substrate. For example an affinity between the adhesive and the first surface can be relatively poor reducing a resulting bond strength between the first and the second substrates. In some designs, there may be little flexibility in adhesive choice because of operating conditions or assembly limitations, for example.
In one embodiment a bond surface on the first substrate can be ablated by a laser. The ablation can increase the average surface roughness to a predetermined amount. In another embodiment, the first substrate can be formed from a filled polymer resin. Laser ablation of a filled polymer resin can remove a smooth skin on the first substrate that can be a result of a molding (such as injection molding) operation and can expose at least a portion of the filler material included in the filled resin polymer. In another embodiment, a bond surface on the first and the second substrates can be laser ablated prior to an application of an adhesive to bond the first substrate to the second substrate.
Laser ablation can increase a surface roughness on the bond areas of the first and second substrates, and thereby increase bond strength in the bond areas. In one embodiment, laser ablation can increase an average surface roughness of the bond area to a predetermined amount. In one embodiment, first substrate can be molded from composite material such as a filled polymer resin. Oftentimes, molded composite parts can include a relatively smooth outer layer relatively rich in resin material, especially when compared to the bulk of the molded part. Laser ablation can increase the average roughness of the outer layers of molded composite parts.
Laser ablation of the bond areas of the first and the second substrates can provide more adhesive choices to the designer. The bond performance, in this example, is no longer limited to the bond strength between the adhesive 104 and the first substrate 102. Laser ablation of the first substrate can alter surface roughness, surface chemistry and surface composition and thereby affect the material in contact with adhesive 204. Thus, in some embodiments, bond strength can be increased substantially by laser ablation.
The rear cover 504 can include at least one opening 510 that can receive the processor 524, the battery 522 and the display 520. In one embodiment, the rear cover 504 can include a mounting feature 530 that can be integral to rear cover 504, or can be formed of a material different from the rear cover 504 and secured in place with any technically feasible means such glue, epoxy, welding or the like. The front cover 502 can be configured to substantially fit within at least one opening 510 in the front cover 502. At least one bond area is shown within area 506. In one embodiment, mounting feature 530 can be laser ablated prior to the application of an adhesive 532 to the mounting feature 530. Front cover 502 can be affixed to the adhesive 532. In one embodiment, bond areas on the front cover 502 can be laser ablated prior to the application of adhesive 532.
The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as computer readable code on a computer readable medium for controlling manufacturing operations or as computer readable code on a computer readable medium for controlling a manufacturing line. The computer readable medium is any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.
The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.
