BS EN 62047-14:2012 pdf download – Semiconductor devices — Micro-electromechanical devices Part 1 4: Forming limit measuring method of metallic film materials
This part of lEC 62047 describes definitions and procedures for measuring the forming limit ofmetallic film materials with a thickness range from 0,5 um to 300 um. The metallic filmmaterials described herein are typically used in electric components,MEMS and micro-devices.
When metallic film materials used in MEMS(see 2.1.2 of lEC 62047-1:2005) are fabricated bya forming process such as imprinting, it is necessary to predict the material failure in order toincrease the reliability of the components. Through this prediction,the effectiveness ofmanufacturing MEMS components by a forming process can also be improved, because theperiod of developing a product can be reduced and manufacturing costs can thus bedecreased. This standard presents one of the prediction methods for material failure inimprinting process.
2Normative references
The following documents, in whole or in part, are normatively referenced in this document andare indispensable for its application.For dated references,only the edition cited applies. Forundated references, the latest edition of the referenced document(including anyamendments) applies.
IEC 62047-1:2005,Semiconductor devices – Micro-electromechanical devices – Part 1:Terms and definitions
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document,the terms and definitions given in IEC 62047-1 and thefollowing apply.
circular grid
grid used for measuring the localized deformation of the specimens within the circle
grid patterns
pattern marked on the surface of the testing material permitting immediate and directmeasurement of the formability for the metallic film materials
Note 1 to entry The grid consists of a pattern of small circles or rectangles.
major axis
longest line of the deformed elliptical shape,which passes through both focuses of the ellipse
4 Testing method
4.1 General
The forming limit diagram (FLD) is determined by pressing the micro film material using a hemispherical punch. This pressing process is performed until the film material fractures. The major and minor strains of a deformed specimen can be measured in many ways, for example, by using a digital camera module or an optical device. However, using a digital camera module with sufficient resolution and a high magnifying power lens is recommended. NOTE See Annex A for principles of forming limit diagram.
4.2 Equipment Micro press equipment is utilized as the loading equipment for FLD tests as described in Figure 1 . A hemispherical punch is attached to the micro press to stretch the film material to measure the forming limits of the specimen. Conventional hard chrome coating to the punch surface using hexavalent chromium is recommended to guarantee a surface roughness less than 0,8 µm (RMS: Root Mean Square). In addition, lubricants such as graphite can be applied for reducing the friction force between the surfaces of the punch and the specimen. The movement of the punch is controlled by a constant crosshead speed of the measuring devices in the micro press. The punch speed shall be lowered to the quasi-static condition. A punch speed of less than 20 µm/s is recommended in order not to result in the dynamic inertia effect during the test. Although the dimension of the hemispherical punch and the test samples can be varied with forming product and inspected measuring region, it is recommended that the dimension should be determined as the following ratio.
D die = D punch + 2,5t (1)
D bead = 2 × D punch (2)
It is also recommended that the hemispherical punch diameter and the die edge radius should be 5 mm and 0,5 mm respectively.
4.3 Specimen Rectangular specimens with different aspect ratios shall be used in the test. At least six kinds of specimens with the aspect ratios of 1 ,0, 1 ,5, 1 ,75, 2,0, 3,5 and 7,0 are recommended as shown in Figure 2 in order to cover the various loading paths on the domain of the forming limit diagram.