ONE of the aspects of the continuous miniaturization in

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1 IEEE TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGIES, VOL. 28, NO. 3, SEPTEMBER SMT-Compatibility of Adhesive Flip Chip on Foil Interconnections With 40-m Pitch Hans de Vries, Jan van Delft, and Kees Slob Abstract The manufacturing and reliability of a novel type of first-level interconnections is described. Anisotropic conductive and nonconductive adhesives are used to electrically bond flip chip ICs with a pitch of 60 and 40 m to flexible substrates. Analyses cover the initial state of the samples as well as their performance in the JEDEC moisture sensitivity level assessment and subsequent life testing. From the different behavior of the two types of adhesives a failure mechanism issues for the reflow-soldering test. Index Terms Anisotropic conductive adhesive (ACA), endurance test, failure mechanism, flip-chip-on-foil, moisture sensitivity level assessment (MSLA), nonconductive adhesive (NCA), reflow soldering. I. INTRODUCTION ONE of the aspects of the continuous miniaturization in modern electronics is the reduction of the first-level interconnection pitch. In particular novel interconnection methods are of interest to achieve this goal. Among these, the use of adhesives instead of solder and of foils (flexible substrates) instead of rigid substrates to connect flip chip ICs has received much attention [1] [8]. In previous studies, we have reported on the reliability of such assemblies with a pitch from 300 m down to 100 m [9], [10]. It was concluded that 100- m pitch assemblies are reliable, and that prospects for making smaller pitches are good. In the meantime, several authors have reported on pitches of 80 m [3] [5], [7], [8] and even 54 m [6]. Comparatively little attention is paid to the surface mount compatibility of these type of products. This concerns their ability to withstand a reflow soldering step. Here only four papers have been published dealing with pitch assemblies 300 and 200 m [9], 100 m [10], and 80 m [7], [8], respectively. In one of these studies [7], [8], one observed an increase of the contact resistance by 30% to 100% depending on the bump height directly after reflow testing. The number of open joints depended strongly on the peak temperature of the reflow step. The underlying mechanism is supposed to be the thermal expansion mismatch between the adhesive matrix and the conductive particles. During subsequent humidity testing at 85 C/85%RH for 500 h, the resistance increased further, which was attributed to a decreasing contact area by swelling of the adhesive as it takes up water. It must be noted that usually one applies moderate bonding pressures, leaving a gap between Manuscript received February 18, 2004; revised September 29, This work was supported by the European Commission under EC Project Cirrus (IST ). This work was recommended for publication by Associate Editor Chin C. Lee upon evaluation of the reviewers comments. The authors are with the Philips Center for Industrial Technology, 5600MD Eindhoven, The Netherlands ( j.w.c.de.vries@philips.com). Digital Object Identifier /TCAPT Fig. 1. Schematic of flip chip on foil assembly. the bumps and the tracks on the foil-substrate that is bridged by the conductive particles in the adhesive. Applying higher pressures will lead to a more intimate contact between bump and bond pad, a prerequisite to make good interconnections with nonconductive adhesives, which is our aim for small pitches. As for our own work [9], [10], the assemblies were preconditioned and tested according to JEDEC standards [11], [12]. From our failure analyses and the material properties a mechanism was derived based on the moisture diffusion coefficients of the foil and the adhesives [9], [10]. Upon subjecting the samples to a reflow soldering profile, and by virtue of the large free area of the foil (see schematic of the assemblies in Fig. 1), the water is forced out from the adhesive through the foil. To pass through safely, the ratio of the water diffusion rates between the adhesive and the foil must not be too large. Should this be the case, water vapor will accumulate at the adhesive die and adhesive foil interfaces, thus causing delamination. The right combination of materials will determine whether or not the chip-on-foil assemblies will pass the tests. The absolute amount of water that is absorbed is of lesser importance. The present work continues the reports on the processing and reliability of flip chip on foil assemblies with adhesive interconnections, with a pitch of 60 and 40 m. We address their compatibility with surface mount technology and durability. II. EXPERIMENTAL ASPECTS Fig. 1 shows the schematic construction of the flip chip on foil assembly. Details are given in the paragraphs below. A thinned die is adhesively bonded on a foil. This first-level interconnection is routed to the second-level solder bumps arranged in a ball grid array. The opposite face of the foil is free to the environment. A. Materials Test dies 5 5 mm were used with either 60- or 40- m bump pitch. Electroplated bumps with a height of 15 m were provided by a commercial supplier, dimensions: m (60- m pitch), m (40- m pitch). The number of bumps per die is 256 and 384, respectively. The wafer thickness was 540 m. Part of the wafers was grinded to a thickness of /$ IEEE

2 500 IEEE TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGIES, VOL. 28, NO. 3, SEPTEMBER m. This was done in a two-step process (coarse fine). As a result of the grinding process, the top layer of the wafers contains a lot of stress and microcracks. About 10 m of the top layer was removed by spin etching in order to improve the die strength, resulting in a final thickness of 160 m. As base material for the polyimide flex foil, Espanex was chosen because of its high water diffusion rate, which is beneficial for its performance in temperature and humid conditions. The foil thickness is 40 m, the outer dimensions are mm. On each foil four flip-chip bonding positions are present. The build-up of the metallization on the foil is: 12 m Cu, 2 m Ni, and 60-nm Au. A solder resist layer was applied around the die positions (thickness 12 m). At the edge of the foil a connector can be attached for electrical measurements. Anisotropically conductive film (ACF) as well as nonconductive film (NCF) was used for the experiments. They consist of the same epoxy matrix. The ACF was filled with Gold-coated polymer particles (diameter 5 m, density 1.54 particles per cubic millimeter). B. Assembly The ACF or NCF was laminated manually on the foil using a hot plate with a temperature of about 80 C. The foil, clamped in a metal support frame, was placed on the bonding table of the flip-chip bonder (Toray FC1000). By means of vacuum the foil is stretched over a glass plate, in order to obtain a flat substrate. The bonding settings for the 60- and 100- m pitch samples were: temperature 220 C (in the bond), time 10 s, and pressure 200 N mm (contact area). For the 40- m pitch the pressure was 350 N mm because of the tapered tracks making the contact area smaller. C. Electrical Characterization and Testing For examining the assemblies conformance with reflow soldering in surface mount technology, a moisture sensitivity level assessment (MSLA) was carried out. The samples are subjected to a certain well-defined humid environment (MSL-3: floor life of 168 h at 30 C/60%RH, with an accelerated soak requirement of 40 h at 60 C/60%RH), and then they pass three times through a reflow oven. This forms part of a set of standardized procedures to expose an electronic package to such conditions that make it possible to simulate the actual stresses it will experience during shipping and second-level mounting [11], [12]. Before and after this treatment a control parameter is measured which must not change as a result of the moisture and temperature shock. In the present case, this parameter is the electrical resistance of the contacts between the IC and the flexible substrate. As for endurance testing, it recently became clear that humidity is a governing factor in the degradation of this type of interconnection; in fact cyclic exposure to humid conditions appeared to be the most severe test condition [13], [14]. Therefore, the samples were subjected to the following stress tests: accelerated humidity test (IEC68-2-3, test Ca: 85 C/85%RH) and the highly accelerated stress test HAST (110 C/85%RH). Periodically they were taken out of the climate chamber for electrical measurements. For the 60- m pitch assemblies the Ca test was done on the samples with dies of 0.16-mm thickness, while the Fig. 2. Distribution of initial single contact resistance values. HAST was reserved for the supposedly stronger assemblies with thicker dies of 0.54 mm. In case of the 40- m pitch assemblies both tests were done. The following tests were done: a qualification test to determine the yield of the samples after a specified period of testing. Further, the lifetime was estimated by continuing these tests until a failure distribution could be made. For the accelerated humidity test the qualification time is 1000 h, and for the highly accelerated stress test this is 264 h. The end of life is arbitrarily defined as the time when the resistance has increased by a factor of ten compared to the initial value. Note, that the contact then is still conducting. The test samples were designed such that for each IC the resistance of eight individual contacts (hereafter called single contacts) could be measured by means of a Kelvin structure. One Kelvin structure incorporates four interconnections. Four of these are located near the corners of the die, the other four in the center of each side. The remaining contacts (224 and 352 for the 60- and 40- m pitch samples, respectively) were connected to form two intertwined chains of contacts, so-called daisy chains. The chains resistance was measured in a twopoint mode while the single-contact resistance was determined in the four-point mode. For the offline resistance measurements the flip chip-foil assemblies were connected to a data acquisition system. The resolution of the resistance measurements is 1 m (voltmeter resolution 10 V, measuring current 1 ma); the precision (repeatability) is in the range of 2-5 m. III. RESULTS In Figs. 2 and 3, the distribution of the resistance values before and after the MSLA test is shown. There is a clear difference in the resistance values for the two pitches, the smaller pitch having a slightly higher resistance. Note, that all the contacts shown in Fig. 3 are good, but the data of the sample labeled thin 60- m A partly lie off the scale. The appropriate yield numbers are listed in Table I for single contacts and in Table II for daisy chains. The monitoring of the resistance values of individual contacts is shown in Figs. 4 7 for a selection of the endurance experiments. In particular in Fig. 4 the gradual increase of the contact resistance can be seen. It should be noted that the vertical scale of Fig. 4 is a factor of ten larger than in Figs In these ACF-samples the resistance values exhibit a larger spread than in the corresponding NCF-samples (see Fig. 6). Still, the time

3 DE VRIES et al.: SMT-COMPATIBILITY OF ADHESIVE FLIP CHIP ON FOIL INTERCONNECTIONS WITH 40- m PITCH 501 Fig. 3. Distribution of single contact resistance values after MSL3 test. Fig. 5. Die thickness 0.16 mm, 60-m pitch, NCF, 85 C/85%RH. TABLE I SINGLE CONTACTS (KELVIN STRUCTURES). YIELD NUMBERS FOR THE VARIOUS ASSEMBLIES (TYPE OF ADHESIVE, PITCH, AND DIE THICKNESS) BEFORE AND AFTER MSLA. INITIAL NUMBER OF MEASURED CONTACTS BEFORE (N), AFTER MOISTURE, AND REFLOW TEST (MSL-3), AFTER 1078 h 85 C/85%RH (AHT), AND AFTER 264 h 110 C/85%RH (HAST). THE 40-m PITCH SAMPLES WERE EQUALLY DIVIDED OVER THE TWO STRESS TESTS. N.A.: TEST NOT CARRIED OUT (SEE TEXT) Fig. 6. Die thickness 0.16 mm, 40-m pitch, NCF, 85 C/85%RH. TABLE II AS TABLE I FOR DAISY CHAINS (SEE TEXT ON EXPERIMENTAL ASPECTS FOR EXPLANATION) Fig. 7. Die thickness 0.16 mm, 40-m pitch, NCF, 110 C/85%RH. Fig. 4. Die thickness 0.16 mm, 60-m pitch, ACF, 85 C/85%RH. Note different vertical scale compared to Figs evolution of these resistance values does not behave in an irregular way with respect to earlier experiments on 100- m [10] and m pitch assemblies [9]. The corresponding Weibull failure distributions, based on the aforementioned criterion of an increase by a factor of ten, are given in Figs From the statistical analyses the Weibull shape (width of the distribution, ) and scale (position of 63% Fig. 8. Weibull distributions. Die thickness 0.54 mm, pitch 60 m: ACF ( ), NCF ( ). 110 C/85%RH. failures, ) parameters are obtained and listed in Table III together with previous results on 100- m pitch assemblies [10]. One should note the difference with Tables I and II, which list the qualification results at the specified times, while here the lifetime data are given resulting from the continued endurance tests. In one case (60- m pitch ACF; see Fig. 8) a multiple

4 502 IEEE TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGIES, VOL. 28, NO. 3, SEPTEMBER 2005 Fig. 9. Weibull distributions. Pitch 40 m, NCF: die thickness 0.54 mm (), 0.16 mm (). 110 C/85%RH. Fig. 11. A 40-m pitch sample with NCF, initial situation. Fig. 10. Weibull distributions. Die thickness 0.54 mm: pitch 60 m: NCF ( ), pitch 40 m: NCF (), pitch 100 m: ACF () [10]. 110 C/85%RH. TABLE III WEIBULL PARAMETERS (SHAPE, SCALE ) AS DERIVED FROM FIGS TEST: 110 C/85%RH/2400 h. DATA FOR 100-m PITCH ARE FROM [10]. IN ONE CASE A DOUBLE FAILURE DISTRIBUTION WAS FITTED. A: ACF, N: NCF failure distribution was fitted to the experimental data and accordingly listed in Table III. This distribution also contains some early failures that were not fitted with a Weibull distribution. IV. DISCUSSION A cross section of a sample bonded with NCF is shown in Fig. 11. One can see the very intimate contact between the bump and the track that is necessary to make an electrical contact with nonconducting adhesives. The data presented in Tables I and II show a very high yield for all sample variations. In the 60- m pitch assemblies none of the single contacts failed in the reflow test. One of the daisy chains failed. As for the 40- m pitch samples, all single contacts survived the reflow test, while two daisy chains became interrupted. From the box and whisker diagrams of Figs. 2 and 3, we infer that in the assemblies with anisotropic conductive adhesive the width of the resistance distribution and the absolute values both increase. In contrast, for the nonconductive adhesive with 40- and 60- m pitch the distributions remain constant but the level of the resistance tends to decrease. In the paragraphs following the discussion of the endurance tests, we propose a mechanism to explain this difference. For comparison, in the assemblies with a pitch of 100 m the yield after the reflow test was 100% for dies of 0.54-mm thickness, and 80% for dies of 0.16-mm thickness [10]. The main reason for the present higher yield with thinned dies is connected with the improved thinning process in which after grinding the damaged top layer is removed by spin etching. As pointed out [9], [10] the resistance of the products against the reflow treatment is governed by the right combination of materials (foil and adhesive) with respect to their water diffusion rate. This will ensure safe transfer of accumulated water without inflicting damage to the construction. Since we have used the same materials for the smaller pitches as well, the good result of the MSLA test is understandable. In the subsequent humidity stress tests on the assemblies with a pitch of 60 m no further failures of the single contacts and the daisy chains were detected at the qualification limits of 1000 h at 85 C/85%RH or 264 h at 110 C/85%RH. Two single contacts and one daisy chain of the 40- m pitch samples failed in the highly accelerated stress test. Continuation of the endurance tests served to further investigate the failure mechanism of the adhesive interconnections. Note the scale difference between the conducting (Fig. 4) and the nonconducting adhesive assemblies (Figs. 5 7). This is directly connected to the difference in the distributions of the resistance values that were measured after the reflow test, as shown in Fig. 3. As for the time evolution of the resistance values, these do not deviate from each other in the sense that we do not find a more irregular behavior in the sample based on conducting adhesive. It further appears that in the examples of the humidity stress test for the conducting adhesive and the highly accelerated stress test for the nonconducting adhesive (Fig. 7) a number of contacts begin to fail. However, only the latter type

5 DE VRIES et al.: SMT-COMPATIBILITY OF ADHESIVE FLIP CHIP ON FOIL INTERCONNECTIONS WITH 40- m PITCH 503 Fig. 12. A 40-m pitch sample with NCF after 110 C/85%RH/2400 h. of test resulted in enough failures to make failure distributions as shown in Figs The gradual degradation in the subsequent stress tests is very probably caused by the progressive decline of the initially present compressive force [9], [14]. It is known that the electrical resistance decreases with the applied pressure [15] [17]. This allows the resistance to increase without actual visible damage, such as delamination of the adhesive layer from the surfaces or a gap between the bumps and the contact pads, in accordance with our observations on cross sections. The 40- m pitch assemblies have a failure distribution that is very much comparable to the 100- m type, as follows from Fig. 10 and Table III. It makes no difference whether thick or thinned dies are used (see Fig. 9). It is therefore very likely that the same failure mechanism is present in these packages. Quite unexpectedly the failure distributions of the 60- m versions are different in two ways. Compared to the smaller and larger pitch samples, their distributions have a different width (Fig. 10). Besides, Fig. 8 shows that the use of conductive or nonconductive adhesive does matter. Whereas with NCF the distribution is monomodal (apart from one early failure) there is a kind of cross over between two distributions, and there is a long tail with early failures. As for the cause of the early failures, misalignment during the manufacturing process could be ruled out. Other causes could not be found. There is no unambiguous explanation for the bimodal distributions yet. In earlier work [10] on 100- m pitch ACF assemblies, it was conjectured that either flaws are introduced by applying (too) high bonding forces, or elastic stress stored during the bonding process relaxes. Results obtained with moderate bonding forces could be fitted with a monomodal failure distribution. Figs. 11 and 12 show the cross section of a 40- m pitch NCF sample before and after testing. No damage is visible. In contrast with this, the analysis of the 60- m ACF samples does reveal some damage. In Fig. 13, a slight lifting of the bump from the track can be seen, and this is even stronger in the example of Fig. 14. The phenomenon is very likely caused by the conductive polymer particles as will be explained below. The following reasoning forms the base of the mechanism that might account for the different behavior of conducting and Fig. 13. A 60-m pitch sample with ACF after 110 C/85%RH/2400 h. Fig. 14. A 60-m pitch sample with ACF after 110 C/85%RH/2400 h. nonconducting adhesives. The glass transition point of the adhesive s matrix is in the range of 120 C to 130 C, while that of the Au-clad particles can typically be well above 300 C. During the soldering process with peak temperatures between 220 C and 250 C, the particles will retain their elasticity and relatively low thermal expansion coefficient, while the matrix of the adhesive with a lower glass transition point will temporarily have a low elasticity and accordingly higher thermal expansion. The connection between the bump and the track can thus become partly lost during heating up, and the stiffer filler particles in the absence of an external pressure will hamper restoration of the connection upon cooling down. In the absence of the above filler particles, these will not hamper the reconnection between bump and track, and the renewed connection will be better than with filler material. An endurance test will sharpen the differences between both types of adhesives. To check this assumption, pressure was reapplied to a selected degraded sample and its resistance measured. This particular sample (60- m pitch, ACF, 0.54 mm-die thickness) was previously subjected to 110 C /85%RH for 2400 h, when the resistance was m. At the beginning of the test this was 4 m. Keeping the pressure constant for 2 3 min, the resistance was recorded as shown in

6 504 IEEE TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGIES, VOL. 28, NO. 3, SEPTEMBER 2005 increase of the electrical resistance. In the 60- m samples this also holds, but the previously mentioned mechanism of transition through the glass point of the polymer filler particles results in a more complicated failure distribution. Fig. 15. Resistance as function of reapplied pressure in degraded contact (60-m pitch, ACF, die thickness 0.54 mm). Fig. 15. Finally, a resistance of a few milli-ohms was reached. It will be clear that this mechanism needs further study. An alternative explanation states that the conductive particles prevent the bump and the substrate to touch, which obviously is not the case for nonconductive adhesive. Then the electrical contact is formed by a number of point contacts. However, the cross sections show that there is a very close contact even in the presence of conductive particles, as was shown in more detail elsewhere [10], [14]. Moreover, the number of trapped particles is about in a 100- m pitch contact of m and presumably proportionally lower in the present contacts. Hence, the low trapped-particle density and the relatively high bonding pressure will prevent the particles to form a gap between the bump and the track. In the 100- m pitch samples with the same type of ACF [10] no such mechanism was observed. In comparison with the 60- m pitch samples, there was a much more intimate contact between the bumps and the tracks, effectively disabling the conductive particles. Hence, the 40- m pitch NCF assemblies better resemble the 100- m ACF type than the 60- m ACF type. V. CONCLUSION Although the combination of moisture and thermal shock form a severe stress load to adhesively bonded flip chip on foil interconnections, their reliability is good. This study has shown the feasibility in the moisture and reflow soldering test of such assemblies with a first-level pitch down to 40 m. The yield from the MSLA test (level 3) is 100% for individually measured contacts, and 100% for daisy chains with 112 bumps (60- m pitch) and 93% to 100% in chains of 176 bumps (40- m pitch). Using the proper combination of foil and adhesive, the absorbed water can be expelled without damaging the interconnections. The larger spread of the resistance values after the MSLA test in the 60- m pitch samples with ACF compared to the 40- m pitch NCF type is attributed to the different glass transition points of the adhesive matrix and of the polymer filler particles. This leads to a less good contact between the bumps and the tracks in the case of ACF while the mechanism is absent in the NCF products. The failure mechanism of the 40- m pitch NCF assemblies in the stress tests is similar to that in the 100- m and larger pitch ACF assemblies. Relaxation of the contact force, caused by thermal and moisture-induced stress, is supposed to lead to REFERENCES [1] J. Liu, Recent advances in conductive adhesives for direct flip chip attach applications, Microsyst. Technol., vol. 5, pp , [2] E. Janssen and G. Kums, The development of an industrial technology for flip chip on flex circuitry, in Proc. Semicon Singapore, 2000, pp [3] P. Palm, J. Määttänen, A. Tuominen, and E. Ristolainen, Reliability of 80 m pitch flip chip attachment on flex, Microelectron. Reliab., vol. 41, pp , [4] P. Palm, J. Määttänen, Y. De Maquillé, A. Picault, J. Vanfleteren, and B. Vandecasteele, Reliability of different flex materials in high density flip chip on flex applications, in Proc. 1st Int. I12E Conf. Polymers Adhesives Microelectronics Photonics, 2001, pp [5] S. M. Chang, J. H. Jou, A. Hsieh, T. H. Chen, C. Y. Chang, Y. H. Wang, and C. M. Huang, Characteristic study of anisotropic-conductive film for chip-on-film packaging, Microelectron. Reliab., vol. 41, pp , [6] J. Määttänen, P. Palm, Y. De Maquillé, and N. Bauduin, Development of fine pitch (54 m) flip chip on flex interconnection process, in Proc. IEEE Polytronic, 2002, pp [7] C. Y. Yin, M. O. Alam, Y. C. Chan, C. Bailey, and H. Lu, The effect of reflow process on the contact resistance and reliability of anisotropic conductive film interconnection for flip chip on flex applications, Microelectron. Reliab., vol. 43, pp , [8] C. Y. Lin, H. Lu, C. Bailey, and Y. C. Chan, Experimental and modeling analysis of the reliability of the anisotropic conductive films, in Proc. ECTC2003, 2003, pp [9] J. de Vries and E. Janssen, Humidity and reflow resistance of flip chip on foil assemblies with conductive adhesive joints, IEEE Trans. Compon. Packag. Technol., vol. 26, no. 3, pp , Sep [10] J. de Vries, J. van Delft, and C. Slob, Quality and reliability of 100 m pitch flip chip ICs on flexible substrates with adhesive interconnections, Microelectron. Rel., vol. 45, pp , [11] IPC/JEDEC, Preconditioning of plastic surface mount devices prior to reliability testing, IPC/JEDEC, Arlington, VA, JESD22-A113, Mar [12] IPC/JEDEC, Moisture/reflow sensitivity classification for nonhermetic solid state surface mount devices, IPC/JEDEC, Arlington, VA, J-STD- 020-B, Jul [13] J. Caers, X. J. Zhao, G. Leekens, R. Dreesen, K. Croes, and E. H. Wong, Moisture induced failures in flip chip on flex interconnections using anisotropic conductive adhesive, in Proc. Int. I12E Conf. Business of Electronic Product Reliability and Liability, 2003, pp [14] J. de Vries, Failure mechanism of anisotropic conductive adhesive interconnections in flip chip ICs on flexible substrates, IEEE Trans. Compon. Packag. Technol., vol. 27, no. 1, pp , Mar [15] R. Divigalpitiya and P. Hogerton, Contact resistance of anisotropic conductive adhesives, in Proc. IMAPS2003, 2003, pp [16] S. X. Wu, K. X. Hu, and C. P. Yeh, Contact reliability modeling and material behavior of conductive adhesives under thermomechanical loads, in Conductive Adhesives for Electronics Packaging, J. Liu, Ed. Isle of Man, U.K.: Electrochemical Publications, 1999, ch. 6. [17] J. F. J. M. Caers, X. J. Zhao, E. H. Wong, C. K. Ong, Z. X. Wu, and R. Ranjan, Prediction of moisture induced failures in flip chip on flex interconnections with nonconductive adhesives, in Proc. 53rd ECTC Conf., 2003, pp Hans de Vries received the Ph.D. degree in physics from the State University of Leiden, Leiden, The Netherlands, in While at Philips Research Laboratory, he worked on electrical conduction of thin metallic films and high-t superconductors. From 1989 until 2000, he was with the Philips Components division active in development of electro- and piezo-ceramic components. Since 2000, he has been with the Philips Center for Industrial Technology, Eindhoven, The Netherlands, working on reliability of electronic packages and interconnections.

7 DE VRIES et al.: SMT-COMPATIBILITY OF ADHESIVE FLIP CHIP ON FOIL INTERCONNECTIONS WITH 40- m PITCH 505 Jan van Delft received the B.Sc. degree in chemical technology from the Eindhoven University of Professional Education, Eindhoven, The Netherlands, in While at Philips, he was active in interconnect technology for flat-panel displays until Since 2000, he has been with the Philips Center for Industrial Technology, Eindhoven, working on interconnections of chips and foils on rigid and flexible substrates. Kees Slob finished his study in physical chemistry in 1987 at the State University of Utrecht, Utrecht, The Netherlands. From 1987 to 1992, he investigated high-density magnetic recording at Philips Research. In 1992, he started at the Philips Center for Industrial Technology. Eindhoven, The Netherlands, and worked in the field of structural adhesives. Since 1998, the focus of his activities is on interconnect and packaging technology for microelectronic modules.