1、JEDEC STANDARD Test Method for the Measurement of Moisture Diffusivity and Water Solubility in Organic Materials Used in Electronic Devices JESD22-A120B (Revision of JESD22-A120A, January 2008) JULY 2014 JEDEC SOLID STATE TECHNOLOGY ASSOCIATION NOTICE JEDEC standards and publications contain materia
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7、C at the address below, or refer to www.jedec.org under Standards and Documents for alternative contact information. Published by JEDEC Solid State Technology Association 2014 3103 North 10th Street Suite 240 South Arlington, VA 22201-2107 This document may be downloaded free of charge; however JEDE
8、C retains the copyright on this material. By downloading this file the individual agrees not to charge for or resell the resulting material. PRICE: Contact JEDEC Printed in the U.S.A. All rights reserved PLEASE! DONT VIOLATE THE LAW! This document is copyrighted by JEDEC and may not be reproduced wi
9、thout permission. For information, contact: JEDEC Solid State Technology Association 3103 North 10th Street Suite 240 South Arlington, VA 22201-2107 or refer to www.jedec.org under Standards-Documents/Copyright Information. JEDEC Standard No. 22-A120A Page 1 Test Method A120B (Revision of A120A) STA
10、NDARD TEST METHOD FOR THE MEASUREMENT OF MOISTURE DIFFUSIVITY AND WATER SOLUBILITY IN ORGANIC MATERIALS USED IN ELECTRONIC DEVICES (From JEDEC Board Ballot JCB-14-30, formulated under the cognizance of the JC-14.1 Subcommittee on Reliability test methods for packaged Devices.) 1 Scope The purpose of
11、 this test method is to provide a means for determining the moisture sorption properties of organic materials used in the packaging of electronic devices. This specification details the procedures for the measurement of characteristic bulk material properties of moisture diffusivity and water solubi
12、lity in organic materials used in the packaging of electronic devices. These two material properties are important parameters for the effective reliability performance of plastic packaged surface mount devices after exposure to moisture and subjected to high temperature solder reflow. 2 Normative re
13、ferences J-STD-020, Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices. ASTM Standard D570-10, Standard Test Method for Water Absorption of Plastics. SEMI G66-0811, Test Method for the Measurement of Water Absorption Characteristics for Semiconductor Plastic
14、 Molding Compounds. DIN EN ISO 62: 2008, Plastics Determination of Water Absorption. SEMI MS10-0812, Test Method to Measure Fluid Permeation through MEMS Packaging Materials. 3 Apparatus 3.1 Analytical balance capable of resolution of either 0.00001g or 0.001% of sample weight. 3.2 High temperature
15、oven capable of maintaining uniform temperatures from 100 C 250 C +/-2 C. 3.3 Temperature / humidity chamber(s) capable of maintaining temperatures of 30 C 85 C and relative humiditys from 60%RH 85%RH. Within the chamber working area, temperature tolerance must be +/-2 C and the RH tolerance must be
16、 +/-3%RH. 3.4 Perforated stainless steel trays or wire mesh baskets used for holding samples and for placement into ovens. 3.5 Large aluminum plate or disk used for heat sink capability. 3.6 Desiccator for holding dry samples. JEDEC Standard No. 22-A120B Page 2 Test Method A120B (Revision of A120A)
17、4 Test samples 4.1 Test samples must be flat parallel-sided discs or coupons. The linear dimensions must be accurately measured to within 0.02mm. 4.1.1 To approximate one-dimensional diffusion behavior with edge effects limited to less than 5% of the total diffusional moisture mass uptake, the free
18、surface area in the thickness dimension must be less than 5% of the flat-sided free surface area of the sample. For a disc of radius r, and thickness h, the following relation must be met: h 0.05r (1) for a coupon of length L, and width W, )()(05.0LWLWh+(2) Recommended sample thickness should be in
19、the range from 0.3 1.0mm. It is recommended that the maximum sample thickness not exceed 1.0mm, because the time to achieve moisture saturation at temperatures below 60C will be excessively long for slow diffusing compounds. 5 Procedure 5.1 Sample preparation 5.1.1 Prepare samples by using proper pr
20、ocessing parameters as recommended by the material supplier. 5.1.2 Process and cure the samples using recommended processing conditions per the manufacturers specification. 5.1.3 To obtain the appropriate sample thickness as given by relations (1) or (2), samples may be sectioned and finely polished
21、 from larger bulk specimens. Care must be taken to maintain near-parallel sided flatness for samples prepared in this manner. 5.1.4 The prepared samples should be inspected for voids by Acoustic Microscopy (AM) or x-ray, both internal and surface. The ideal samples must be 95% of theoretical maximum
22、 density. 5.2 Absorption measurements below 100 C 5.2.1 Measure the linear dimensions of the prepared sample to the nearest 0.02mm. Record the sample thickness, h, and calculate the sample volume, Vol, using the appropriate geometric relationship based on the sample shape. NOTE Calculating the volum
23、e by measuring the linear dimensions is never accurate. The error is smaller when the sample is big. One accurate way of determining the volume is to use Archimedess principle, which is to measure the sample weight in air and immersed in a liquid with known density (alcohol, IPA, etc.). In this way,
24、 volume of a sample with irregular shape can also be determined. JEDEC Standard No. 22-A120B Page 3 Test Method A120B (Revision of A120A) 5.2 Absorption measurements below 100 C (contd) 5.2.2 The dry weight of the sample shall be determined, as per J-STD-020, first by baking the sample for 24 hours
25、at 125 +5/-0 C and continue baking and weigh the sample every 12 hours until no further weight loss is observed to ensure that the sample(s) are dry. The dry weight is determined when no further weight loss is observed, less than 0.002% difference, after two consecutive measurements with a minimum b
26、aking interval of 12 hours. Within 30 minutes after removal from the oven, weigh the sample(s) using the analytical balance equipment in 3.1 and determine the dry weight per 5.2.4. Note: As per J-STD-020, small sample(s) (less than 1.5 mm total height), devices should be weighed within 30 minutes af
27、ter removal from oven NOTE As per J-STD-020, small sample(s) (less than 1.5 mm total height), devices should be weighed within 30 minutes after removal from oven. Remove the sample(s) from the bake oven and immediately cool by placing in contact with the heat sink of 3.5. If more than one sample is
28、to be measured, the samples and heat sink should be placed into a desiccator to limit moisture uptake during the weight measurements. 5.2.3 Weigh the sample according to 3.1 and record weight as DryW(1). Read Points: At the desired read point; remove the sample(s) from the bake oven. Within 30 minut
29、es after removal of the sample(s) from the bake oven, remove the sample(s) from the container and determine their weight using the analytical balance equipment in 3.1. Within 30 minutes after weighing the samples, place them in a clean, dry, shallow container so that the sample bodies do not touch e
30、ach other. Return the sample(s) to the bake oven for the desired time. Continue until the sample(s) have lost all their moisture as determined by the dry weight in 5.2.2. 5.2.5 Place the sample(s) into a stainless steel holder and transfer to a temperature / humidity chamber stabilized at a pre-set
31、temperature and humidity. At accumulative times, remove the sample from the temperature / humidity chamber, cool as per 5.2.3, and measure the sample weight and record as WetW(t). Read Points: The X-axis (time) read points, as per J-STD-020, should be selected for plotting the absorption curve. For
32、the early readings, points should be relatively short (24 hours or less) because the curve will have a steep initial slope. Later readings may be spread out further (10 days or more) as the curve becomes asymptotic. The Y-axis (weight gain) should start with 0and increase to the saturated weight gai
33、n. Most sample(s) will reach saturation between 0.3% and 0.4% when stored at 85C/85% RH. Devices shall be kept at room ambient between removal from the oven or chamber and weighing and subsequent reinsertion into the oven or chamber. Care should be taken that no condensed moisture from the chamber w
34、alls comes into contact with a sample during removal from the temperature / humidity chamber. If condensed water should contact a sample, immediately dry the sample using Nitrogen or dry air. The sample should then be returned to the chamber for re-equilibration and another data point taken at a lat
35、er time. The sample weight measurement be made within a few minutes after removal of the sample from the temperature / humidity chamber. Time delays longer than 5 minutes after removal from the temperature / humidity chamber could affect the sample weight measurements. Within 30 minutes after weighi
36、ng the samples, place them in a clean, dry, shallow container so that the sample bodies do not touch each other. Return the sample(s) to the temperature/humidity chamber for the desired time. JEDEC Standard No. 22-A120B Page 4 Test Method A120B (Revision of A120A) 5.2 Absorption measurements below 1
37、00 C (contd) 5.2.6 Place the sample back into the temperature / humidity chamber and continue weight measurements until either of the following conditions are met: 5.2.6.1 Additional weight gain after a 24 hour period is less than 0.002% from the previous measurement. 5.2.6.2 A plot of the moisture
38、mass gain, M(t) = WetW(t) DryW(1), versus time shows a linearly increasing moisture mass gain with time or dM/dt = constant after an initial decreasing change in moisture mass with time as depicted in Figure 1. Figure 1 Example of linearly increasing moisture mass gain 5.2.7 Record the final wet wei
39、ght of the sample as, WetW(f) 5.2.8 Bake the sample again at 125C until dry as determined per 5.2.2. 5.2.9 Record the second dry weight as, DryW(2). 5.2.10 Record the reversible saturated moisture mass as, MSat= WetW(f) DryW(2). NOTE 1 An alternative method to estimate the reversible saturated moist
40、ure mass can be determined by an intercept approach as shown in Figure 2. Using this method the intercept point between the weight gain curve and a linear extrapolation of the linear varying portion of the weight gain curve can be used to estimate the reversible Fickian moisture weight gain response
41、. MoistureMass = WetW(t) DryW(1) Time d(M)/dt = constant JEDEC Standard No. 22-A120B Page 5 Test Method A120B (Revision of A120A) 5.2 Absorption measurements below 100 C (contd) Figure 2 Alternative intercept method to estimate the reversible Fickian moisture mass MoistureMass = WetW(t) DryW(1) Time
42、 MSatd(M)/dt = constant Intercept Point JEDEC Standard No. 22-A120B Page 6 Test Method A120B (Revision of A120A) 5.3 Solubility and diffusivity calculation 5.3.1 Calculate the solubility at the given temperature and humidity by using: Vol),%(T,%RH)CSatRHTMSat= = (Msat/M(mass) (=density) (3) Where: C
43、 Sat(T,%RH) = the moisture solubility at temperature T and %RH (mg/cm3 ) Vol = sample volume (cm3) M Sat(T,%RH) (mg) = reversible saturated moisture mass at temperature T and %RH as determined in 5.2.10 5.3.2 Using the moisture mass gain curve, calculate the moisture diffusivity from: 5.0204919.0)(t
44、hTD = (4) Where: D(T) = the diffusivity at temperature T (mm2/s) h = sample thickness (mm) t0.5= the sorption half-time (measured in seconds) defined as the time at which the sorbed mass of moisture is equal to one-half the saturated mass, i.e., Mt/MSat= 0.5. NOTE 1 Equation (4) is recognized as an
45、approximation to the analytical closed form solution, however, it will provide an accurate approximation to less than a few percent error. An alternate method for determining D(T) is to use a best fit curve fitting approach of the experimental weight gain data. The following solution for rectangular
46、 or square samples can be used: + + +=22220002226)12()12()12()12()12()12()exp(5121oooeqvlmneqvSattznymxlLwherenmlLtDMM(5) Here xo, yo, and zoare the width, length, and thickness of the sample, respectively. The value of D(T) determined by a curve fitting technique using equation (5) should be compar
47、ed to the value determined by equation (4) as a reference check. 5.3.3 Repeat sorption measurements 5.2 to 5.3.2 using different temperature and humidity conditions. The following environmental conditions shall be used: 30 C/60%RH, 60 C/60%RH, and 85 C/60%RH. JEDEC Standard No. 22-A120B Page 7 Test
48、Method A120B (Revision of A120A) 5.4 Desorption measurements above 100 C 5.4.1 Place sample into a chamber maintained at 85 C/60%RH or 85 C/85%RH for 168 hrs or until the saturated sample weight, WSat, is achieved as determined by a calculation using a previously determined diffusivity at 85 C. 5.4.
49、2 Remove the sample from the temperature/humidity chamber, cool as per 5.2.3, and record the saturated sample weight, WSat. 5.4.3 Immediately place the sample into a bake oven stabilized at a temperature greater than 100 C. The sample shall be transferred into a stainless steel holder that has been preheated and stabilized at the set bake temperature. 5.4.4 Remove the sample after a recorded elapsed period of time, immediately cool per 5.2.3, and measure the sample weig
