Gas permeation and temperature effects in laser-induced delamination

Laser-induced delamination (LID) is a technique aimed at measuring the work of adhesion of thin polymer coatings on metal substrates. A laser pulse is used to create a blister that initiates delamination of the film under pressure. The stress fields in the blister wall and the work of adhesion of the interface are determined using a linear elastic model.In this paper we discuss validity of the LID results addressing permeation of gas through the blister wall and the initial high temperature of the substrate. A procedure to account for the effect of gas permeation in the calculations of the work of adhesion is proposed. Permeation of gas is also considered under compressive and tensile in-plane stresses. Modeling of the permeation process demonstrates a good agreement with the experiment.At early stage of the blister formation the metal substrate and the blister gas experience high temperatures. The time scales of the cooling processes are estimated. Possible effects of the high temperatures on the permeation of gas and on the process of delamination are discussed.     

The use of stimulated boundary gas release for determination of the adhesion of thin films by the blister test

The processes of stimulated gas release and gas blister growth were investigated at the interface of 100 nm thick silver films on glass substrates after irradiation by hydrogen ions of 1 MeV energy to fluences of 1 x 10¹³-1 x 10¹⁵ ion cm^-2. An interference microscope was used to examine the gas blisters and to measure the blister parameters. The relationship of these processes to the adhesion of a thin film system was established. A method to determine the adhesion and to compute the adhesion characteristics in the film-substrate system is described. The calculated energy of the detachment ranges between 0.06 and 28 J m^-2. Based on the results of this study, a series of practical approaches are proposed to measure the adhesion of thin films to substrates with the method of stimulated gas release.     

Influence of heat transfer and curing on the quality of pultruded composites. I: Experimental

Blister formation, a major concern in pultrusion, has not been studied in detail. The objective of this study is to investigate the mechanism of blister formation and the effect of process variables such as die temperature, pulling speed, die length, and composite thickness on blister formation. Dies with different length and a stop-start method were used to investigate blister formation. The results show that for a given die and resin system, low temperature and a higher pulling speed lead to blister formation. Longer dies can prevent blister formation. Based on the experimental results, process windows for 4-mm-thick and 6-mm-thick composites are established for a vinyl ester resin. This study suggests that heater power input should be optimized in high-speed pultrusion.     

影响镁铬耐火材料抗粗铜侵蚀的因素

研究了温度、保温时间、粗铜的加入量和气氛等因素对镁铬耐火材料抗粗铜侵蚀性能的影响。结果表明 :随着侵蚀温度的升高 ,侵蚀保温时间的延长和粗铜加入量的增加 ,其渗透面积增大 ;气氛对粗铜渗透性影响较大 ,粗铜熔体中 [O]浓度越高 ,粗铜的渗透性越强。     

Prevention of blister formation in electrolessly deposited copper film on organic substrates

Electroless copper (Cu) plating is a key process to provide seed layers for the subsequent Cu electroplating in the printed wiring boards (PWBs). Due to the demand for lower power dissipation at higher temperatures and high signal frequencies, various kinds of organic materials have been newly introduced as substrates. However, they have come with defects such as delamination and/or blisters in the Cu layers on organic substrates, i.e., weak adhesion. Here we demonstrate the root cause and a prevention method of the blister formation. Various parameters affecting the blister formation have been investigated combined with the deposit thickness (internal stress), hydrogen gas evolution, and codeposited Ni content in the electroless Cu plating. It was not obvious that the compressive internal stress in deposits was directly related to the blister formation. Instead, the hydrogen gas evolution clearly turned out to be the key factor, and it was observed that Ni added plating solutions reduced the hydrogen gas evolution significantly and thus produced no blisters in the Cu deposits. The control of blisters would be more critical as the line and space become narrower in the production lines such as ball grid array (BGA) and high density interconnection (HDI).     

内涂层油管在酸性环境的耐腐蚀性能研究

文中建立了一套酸性气田用内涂层油管耐腐蚀性能评价方法,此方法先考察了内涂层油管在氯离子、氢离子、凝析油、H₂S/CO₂等介质环境的耐渗透性能,再考察了内涂层油管在高温高压高酸性条件下的耐腐蚀性能,配套制定的相关指标,可用于指导内涂层油管应用。结果表明:酚醛环氧内涂层油管具有较好的耐渗透性能,酸性条件下并不改变涂层耐渗透性能;而随着温度的升高及硫化氢分压的升高,涂层失效由阴极剥离失效转变为鼓泡失效。     

Blistering in carbon‐fiber‐filled fluorinated polyimide

A blistering study was performed on a fluorinated polyimide resin and its carbon‐fiber composite in an effort to determine the blister‐formation temperature and the influence of blisters on composite performance. The fluorinated resin and carbon‐fiber composite exhibit higher glass‐transition (435–455°C) and decomposition temperatures (above 520°C) than similar polyimide resins and their carbon‐fiber composites currently used. Two techniques were used to determine moisture‐induced blister formation. A transverse extensometer with quartz lamps as a heating source measured thickness expansion, as did a thermomechanical analyzer as a function of temperature. Both methods successfully measured the onset of blister formation with varying amounts of absorbed moisture (up to 3 wt%) in the samples. The polyimide resin exhibited blister temperatures ranging from 225 to 362°C, with 1.7–3.0 wt% absorbed moisture, and the polyimide composite had blister temperatures from 246 to 294°C with 0.5–1.5 wt% moisture. The blistering effects of the polyimide composites were found to have little correlation with modulus. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

玻璃结壳技术在鼓泡器更换中的运用

鼓泡器对玻璃液的均匀性和消除微气泡有很大帮助,因鼓泡器在玻璃窑炉中使用较少,更换经验不足。现有直接将鼓泡器拉出的方法,危险性极高,成功率低。我公司利用玻璃在低温凝固、高温熔化的原理,保证玻璃液不会外流,使整个更换过程可控,危险性消除,成功率提高。     

Stability Analysis of a Nonlinear Blister Test

The Griffith and stability criteria for the blister test have been derived from thermodynamic arguments. The Griffith criterion includes the stored energy in the blister as well as the interfacial energy change associated with debonding. Based on these criteria an analysis is given of a blister test with a neo-Hookian overlayer debonding from a rigid substrate. A closed analytic form for the strain energy release rate, G, is obtained valid for large elastic deformation of a thin circular film. The criteria derived indicate that quasi-static debonding of the blister is always stable, independent of the interfacial energies and the extent of blister deformation.     

Calendar of events

Printed circuit boards are subject to increasingly hostile environment, for example, to a higher reflow temperature with the new lead-free solders. Consequently, thermal stability of copper clad laminates, a major component in printed circuit boards, is a critical issue in electronic packaging industries. In order to understand thermal degradation behavior, popcorn blister tests were performed at high temperatures for three different brands of copper clads laminated with FR-4 epoxy-saturated glass fabrics. Regardless of the brand, all the specimens became defective with blisters at about 250 °C. Detailed examination of fracture morphology with a scanning electron and an optical interferometric microscope revealed that popcorn blisters started not at the interface between copper foil and epoxy resin but at the interface between epoxy resin and glass yarns inside the FR-4 fabric. Sizing agent, an organic lubricant used for glass fibers, is suspected for the initial breakdown of the interface between glass yarns and epoxy resin. As epoxy resin degraded through decomposition of amino-alcohol portion or some other reaction, the gas products then diffused to the yarn-resin interface area. When the temperature reached about 250 °C, the pressure of such gas pockets became strong enough to rupture the laminate under both tension and shear stresses or to advance the fracture through the epoxy via cleavage fracture. Fracture patterns displayed both river and hackle markings, typical characteristics of epoxy fracture. The river markings seemed to indicate cleavage fracture of the epoxy (mode I) which was in close contact with glass yarns. The hackle markings, on the other hand, suggested rupturing of epoxy under both tension and shear stresses (modes I and II), which were most likely caused by a change in the maximum principal tensile stress direction due to interlocked copper nodules.     

An Elementary Plate Theory Prediction for Strain Energy Release Rate of the Constrained Blister Test

A technique based on elementary plate theory is proposed for estimating the strain energy release rate of the constrained blister specimen for the case of a relatively stiff blister adherend. The results of finite element analysis for an aluminum specimen confirm the applicability of the elementary plate theory approach for the constrained blister test. The paper also proposes an experimental scheme which could be automated to measure the necessary parameters to determine the strain energy release rate of the constrained blister specimen.     

An Elementary Plate Theory Prediction for Strain Energy Release Rate of the Constrained Blister Test

A technique based on elementary plate theory is proposed for estimating the strain energy release rate of the constrained blister specimen for the case of a relatively stiff blister adherend. The results of finite element analysis for an aluminum specimen confirm the applicability of the elementary plate theory approach for the constrained blister test. The paper also proposes an experimental scheme which could be automated to measure the necessary parameters to determine the strain energy release rate of the constrained blister specimen.     

Application of the Island Blister Test for Thin Film Adhesion Measurement

The island blister test has recently been proposed as an adhesion test which allows the peel of thin, well-adhered films without exceeding the tensile strength of the film. The island blister test site is a modification of the standard blister test site, consisting of a suspended membrane of film with an “island” of substrate at the film center. The membrane support and island are secured to a rigid plate and the film is pressurized, peeling the film inward off the island. A model for this inward or “annular” peel indicates that even for systems of good adhesion, peel can be initiated at low enough pressures to prevent film failure by making the center island sufficiently small relative to the size of the film.

We have fabricated island blister test sites using micromachining techniques and have used them to measure the debond energy of polymer films on various substrates. The peel data obtained from these island sites match well to the behavior predicted by a simple fracture mechanics analysis. This paper reports the fabrication of the island test sites, the experimental verification of the test, and the results of application of the test to polyimide films on metallic and polymeric substrates.     

水性吸塑油的研究

在对水性光油研究的基础上,对吸塑包装的工艺、原理进行了深入的分析,考察了吸塑剂、渗透剂、Tg对水性吸塑油使用性能的影响,得到了满足下列使用条件的水性吸塑油:(1)泡壳基材为PVC或PET;(2)纸卡材料为白版纸、白卡纸或铜版纸;(3)热封方式可采用电加热或高周波吸塑热合工艺。该水性吸塑油已经通过工业化生产并上机验证,可满足吸塑粘合要求。     

Application of the Island Blister Test for Thin Film Adhesion Measurement

The island blister test has recently been proposed as an adhesion test which allows the peel of thin, well-adhered films without exceeding the tensile strength of the film. The island blister test site is a modification of the standard blister test site, consisting of a suspended membrane of film with an “island” of substrate at the film center. The membrane support and island are secured to a rigid plate and the film is pressurized, peeling the film inward off the island. A model for this inward or “annular” peel indicates that even for systems of good adhesion, peel can be initiated at low enough pressures to prevent film failure by making the center island sufficiently small relative to the size of the film.

We have fabricated island blister test sites using micromachining techniques and have used them to measure the debond energy of polymer films on various substrates. The peel data obtained from these island sites match well to the behavior predicted by a simple fracture mechanics analysis. This paper reports the fabrication of the island test sites, the experimental verification of the test, and the results of application of the test to polyimide films on metallic and polymeric substrates.     

Analysis of Critical Debonding Pressures of Stressed Thin Films in the Blister Test

This paper reports a model for the relationship between critical debonding pressures and the work of adhesion of thin films in the blister test. Previous models have neglected the possible role of residual stresses in the film on the critical pressure. The model reported here shows that these stresses may have a large effect on the relation between the critical pressure and the work of adhesion. A similar model is developed for an alternative blister geometry, the annular or “island” blister. It is shown that films which cannot be peeled using the standard blister test (due to exceeding the tensile strength limit of the film before initiating a debond) can be peeled by varying the geometric parameters of the island blister.     

Quantification of Coating Adhesion Using Laser Induced Decohesion Spectroscopy

We present a new technique, laser induced decohesion spectroscopy (LIDS), which is capable of measuring the practical work of adhesion G between a transparent polymer coating and an opaque coating or substrate. In LIDS, a laser pulse directed onto the sample creates a blister at the transparent/opaque interface. The blister's internal pressure depends on the laser pulse energy, and at a critical pressure the sample fractures, creating an annular debond similar to that obtained in the standard blister test. By measuring physical variables such as the curvature of the blister, and its radius and thickness, it is possible to deduce G, Here we measure G between an automotive clearcoat and four opaque basecoats of various pigmentations (black, white, red, metallic green) as a function of clearcoat thickness. We find that G depends on pigmentation due to the various pigment volume concentrations (PVC's) and specific pigment-binder interactions. Also, G depends on the clearcoat thickness when the thickness is comparable with the size of the plastic zone, R_p.     

Application of the blister test to the study of polymer–polymer adhesion

This article demonstrates the use of the blister test for measuring the fracture energy, G_a, of the interface between two incompatible polymers. We describe an apparatus in which a fluid was injected at constant rate at the interface between a solid, glassy polymer, and a thin rubbery overcoating to create a “blister.” The fluid pressure and blister geometry were measured as functions of time. An energy balance analysis reveals three independent methods for the calculation of G_a from the data. The method was applied to the system of polyisoprene/poly(methylmethacrylate). We used a sequential debonding procedure to obtain reproducible data following the theoretical predictions. The self-consistency of the data suggested that the adhesion energy could be calculated reliably from the pressure alone, without using the blister geometry.     

工艺参数对铁尾矿制备泡沫玻璃性能的影响

以铁尾矿为主要原料、CaCO3和Na2CO3为发泡剂、Na3PO4×12H2O和硼砂(Na2B4O7×10H2O)为稳定剂,制备了性能良好的泡沫玻璃材料,并研究了工艺参数对制品性能的影响. 结果表明,CaCO3为主要发泡剂,Na2CO3含量对制品性能影响不大;Na3PO4×12H2O为主要稳定剂,Na2B4O7×10H2O含量不宜过多;发泡温度升高使制品孔径变大、容重和抗压强度降低;而烧结温度升高使制品的容重和抗压强度均先减小后增大. 制备泡沫玻璃适宜的工艺参数为(%, w)：基础玻璃84, CaCO3 3, Na2CO3 2, Na3PO4×12H2O 8, Na2B4O7×10H2O 3, 发泡温度900~950℃,烧结温度1100℃. 由此制得的泡沫玻璃材料容重约为2.05 g/cm3,抗压强度达62 MPa左右.     

Micro-mechanic model for cathodic blister growth in painted steel

A micro-mechanic blister growth model is proposed for a coating system consisting of a polymer film applied to a steel substrate exposed to salt solutions. The mechanism of the blister formation is based on corrosion-induced disbondment of the coating at the defect periphery coupled with the stress driven diffusive transport of liquid along the coating/substrate interface. By considering the coating as a semi-double cantilever beam loaded by a moment at the periphery and a distributed load along the beam length due to mass transport, a fifth order ordinary differential equation is derived for the beam deflection. The solution is obtained, which yields the functional relationship between the blister growth rate and applied bending moment. The predicted blister growth velocity compared favorably with experimental observations on a paint coated steel panel immersed in a five percent salt water solution. Model predictions allow the construction of a blistering zone/nonblistering zone map, which should help to design better protective coatings for steel. Fourth Place Winner 1998 Roon Awards Competition. Presented at 1998 Annual Meeting of the Federation of Societies for Coatings Technology, on October 15, 1998, in New Orleans, LA. Building Materials Div., Bldg. 226, Room B350, Gaithersburg, MD 20899-8621.