Adhesion tests stud pull

Adhesion test, stud-pull An adhesion test whereby a protrusion (stud) is bonded to the surface of the film and pulled in tension. 

There are numerous techniques known for adhesion and delamination testing, some of the most common being a tape test, stud-pull test, scratch test, and an indentation test [1]. In the tape test, a tape is pulled off the surface containing a scratch, which provides the failure initiation. In the stud pull test, a stud held with thermosetting epoxy is pulled off the film surface. The indentation test, wherein a ball is pressed into the surface, is used for hard coatings, and the failure pattern indicates acceptable behavior. In the scratch test, where an indenter moves in both vertical (loading) and horizontal (sliding) directions, an acoustic emission sensor allows for detection of the initiation of fiacture, while the scratch pattern indicates the type of failure. 

Pull-outs (adhesion) Regions of the film having poor adhesion, which are pulled out by adhesion tests (tape test, stud-pull test, etc.), leaving pinholes. 

Stud or butt tests representing pull-off tests used for the measiuements of the adhesion characteristics between an ink/paint coating and the substrate. An adhesive is applied to the paint coating, and a metallic stud made of aluminum is glued onto the surface by the adhesive applied to the paint coating. Subsequently, the pull force is utilized perpendicular to the substrate surface with a constant rate. This measurement provides an excellent measurement of adhesion for systems, for example, for polymer-metal interfaces [98]. Figure 8.14 schematically illustrates the puU-off test schematically [99]. 

Direct tensile adhesion test An aluminum stud is mounted on the surface of the coating using a cyanoacrylate adhesive and then pulled to determine debonding force. ASTM D 5179... 

Typically, adhesion testing is done by lot sampling on product or witness samples that are representative of the product. It should be remembered that the properties of the substrate material and surface preparation procedures may have an important effect on the measured adhesion so the witness sample material and its preparation should be representative of the product processing. For example, the product surface may be curved and a witness sample with a flat surface prepared using the same material, surface flnish, surface preparation, and deposition process so that a stud-pull adhesion test can be used. Stressing a film to test for adhesion can result in degradation such as cracking of the fllm, may contaminate the film, or can weaken the interface or substrate. Care must be taken if the tested surface is to be subsequently used as product. 

The time required for the deposition of copper metal on PTra film after immersion into the plating bath was dependent on the number of laser shots employed in the surface modification when the film was irradiated with 3000, 1000, and 500 shots, it required 3,6, and 12 s, respectively. In this process, differing from the case of nickel, the copper metal was plated on the entire PTFE surface, indicating that the activators were deposited on the entire surface by the promoter to improve the adhesion of plating metal and substrate. However, the well-defined image of copper metal appeared on the film after the adherence test with the tape, due to a clear difference between irradiated and un-irradiated regions in adhesion. The adhesive strength between the copper metal and PTFE film was estimated to be 7.8 MPa by the pull-stud test. 

Procedures for this test method are covered in ISO 4624 Paint and Varnish Pull-off Test for adhesion. In preparation for this test a stud, normally made of steel, is glued with the coating and is subjected to axial tension until detachment of the paint film takes place. The result is a maximum tensile stress that is possible at the interface (see Figure 15.6). The maximum shear stress is obtained when a torque is applied about the axis of the stud. 

One of the simplest and most useful tests performed on reflow-attached flip chips to determine the adequacy of the solder joints (i.e., C4) is a tensile pull test (Fig. 31). This is done by adhesively attaching a metal stud to the back of a joined chip and pulling the joints in tension at a slow strain rate (approximately 1.0x10 sec ). The pull force is measured during the test using an appropriate load cell. The pull strength is a useful parameter, but the failure mode is a very important indicator of joint quahty. Planar failure at the solder joint interfaces is indicative of a weak and unacceptable interface condition. 

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