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Humidity indicator card
The most common humidity indicator cards change color from blue (less than indicated RH level)to pink (greater than indicated RH level). Base chemical is cobalt(II) chloride). United States Military Specification Mil-I-8835A is the governing specification for a humidity indicator card. The humidity indicator card is also specified for use in J-STD-033 which is the standard for Handling, Packing, Shipping and Use of Moisture/Reflow Sensitive Surface Mount Devices, also known generically as semiconductors. This is a joint standard developed by the Joint Electron Device Engineering Council and IPC and is used in semiconductor packaging.
Additional recommended knowledge
The need for an easily read humidity indicator that could not be damaged by vibration was identified during World War II. Rear Admiral Welford C. Blinn, at that time the Commander of the USS Pope, became concerned about the poor condition of the weapons and ammunition arriving in the Pacific Theater. High humidity in the South Pacific, coupled with poor packaging methods, was causing corrosion and moisture damage. A significant amount of ordinance was arriving in an unstable, and sometimes dangerous, condition. Following the end of the war R. Admiral Blinn was assigned to Washington, D.C. where he had the use of a research lab. There he developed the concept for the first color change humidity indicator, a simple “go/no-go” method of monitoring humidity.
In the late 1940’s, Relative Humidity in the range of 30-35% was the concern because this is when corrosion can begin. For 50 years, industrial and military applications for color change humidity indicators were the primary market for these products. R. Admiral Blinn founded Humidial Corporation in 1948 Acquired by Süd-Chemie, Inc. in 1989 to commercialize humidity indicators.
In the mid-1980’s decedents of R. Admiral Blinn, began working with manufactures of semiconductors to identify and resolve the problem of “pop corning”. It was determined that the solder mounting of semiconductors, also known as devices, onto boards can cause "pop corning" of certain types of surface mount packages if they have been improperly stored or handled. This package delamination occurs as excessive moisture within the package expands as a result of the rapid thermal changes experienced during solder mount operations. As a result an industry wide standard for packaging of semiconductors was released in 1989. This standard, EIA 583, called for the use of humidity indicator card that would indicate as low as 10%. Adherence to proper storage and handling methods immediately reduced the number of failures in the semiconductors, but over the years it became apparent that even humidity levels under 10% were detrimental to the devices. Once again, the Joint Electron Device Engineering Council (JEDEC), now the standards body for semiconductor packaging, went to the decedents of R. Admiral Blinn to determine the feasibility of making a 5% color change humidity indicator. In April 1999, J-STD-033 was released with a 5, 10, 15% color change indicator card specified.
Cobalt Free Humidity Indicator Cards
Cobalt-free brown to azure(copper (II) chloride base) HIC's can be found on the market. In the year 1998 European Community (EC) has issued a directive (adapting to technical progress for the 25th time Council Directive 67/548/EEC on the approximation of the laws, regulations and administrative provisions relating to the classification, packaging and labeling of dangerous substances) which classifies cobalt(II) chloride compounds containing Cobalt Chloride percentages (w/w) between 0,01 and 1 as an T (Toxic) and R49 (may cause cancer if inhaled). As a consequence new cobalt-free humidity indicator cards have been developed by some companies.
Although the EC issued this directive, it does not ban humidity indicators that contain cobalt(II) chloride which has been a common misconception. The only effect the EC directive has on a humidity indicator card that contains cobalt(II) chloride is setting labeling requirement thresholds. A humidity indicator is considered a preparation in the EC definition and therefore has no labeling requirements if the % of cobalt(II) chloride by weight is <0.25%. The T (toxic) and R49 (may cause cancer if inhaled) is not applicable because a humidity indicator cannot be inhaled.
HICs in Semiconductor Packaging
For semiconductor packaging, HICs are packed inside a moisture-sensitive bag, along with the desiccant, to aid in determining the level of moisture to which the moisture-sensitive devices have been subjected.
JEDEC is the leading developer of standards for the solid-state industry and sets the standards for semiconductor packaging. The latest JEDEC standard, the Joint Industry Standard for the “Handling, Packing, Shipping and Use of Moisture/Reflow Sensitive Surface Mount Devices” J-STD-033B, sets forth the use and testing of humidity indicator cards in the dry packaging of semiconductors. HICs are used to ensure that the humidity within dry packed barrier bags remains at safe levels for surface mount devices. In the past, HICs for the semiconductor industry have indicated relative humidity (RH) levels of 5, 10 and 15 percent. However, JEDEC and IPC released JSTD-033B in 2005, which requires the use of an HIC that indicates RH levels of 5, 10 and 60 percent.
The standard includes the use and testing of humidity indicator (HI) cards in the dry packaging of semiconductors. The methods outlined in the standard are prescribed by JEDEC and IPC to avoid damage—like cracks and delamination—from moisture absorption and exposure to solder reflow temperatures that can result in yield and reliability degradation.
The stipulations of J-STD-003B state:
1) HICs must adhere to a standard, minimum color-change quality level to ensure accuracy and readability between dry and humid states: The Color Meter Test Method, quantitatively determines the accuracy of color change HICs. The levels, as outlined in the J-STD-033B revision, require a “significant, perceptible change in color” between noted humidity levels. Manufacturers are required to test their cards for accuracy using a colorimeter device and be required to provide a test report to the customer certifying that the HIC meets quality requirements.
2) HICs must indicate humidity levels for MSL 2 Parts, in addition to MSL 2a to 5a: Whereas previous cards used a 5, 10 and 15 percent relative humidity spot system to indicate humidity exposure levels for moisture sensitive components, the new HIC will now feature spots indicating 5, 10 and 60 percent. The change means that cards will now indicate humidity exposure for Level 2 MSL devices. Additionally, a positive reading on the 60 percent spot indicates that cards should not be re-used, as the high levels of humidity to which the card has been exposed will jeopardize the accuracy of low (5% RH) readings. The 5, 10, 60 percent cards are complaint with Europen Community Council Directive 67/548/EEC as long as they do not contain more than the applicable amount of cobalt chloride.
The full standard can be downloaded from JEDEC.
Maximum Irreversible Humidity Indicator Cards
Maximum Humidity Indicator Cards are specially designed cards that monitor relative humidity levels in cargo applications. Each level of humidity is represented by a blue crystal that dissolves to create a large blue spot that clearly indicates the highest relative humidity level that has been reached. Maximum Humidity Indicator Cards are irreversible, thus indicating the highest level of humidity experienced by cargo during its voyage, regardless of current (potentially lower) humidity levels. Maximum Humidity Indicator Cards provide a clear, unmistakable means of determining if goods have been exposed to damaging humidity levels during their journey. If the card indicates high levels of humidity, users know check their products for possible damage or modify their packaging regimen accordingly.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Humidity_indicator_card". A list of authors is available in Wikipedia.|