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  1. #1

    what is the color significance of soldermask

    helo all, i have a small doubt regarding the pcb solder mask. is there any significance for pcb soldermask like..most of the pcbs are in green colour, some are in black(i know black is used for some displays systems where light is not to be transperented).I saw some pcbs in Blue and Red color, let me know if any one of u know, in which application the Red and Blue solder mask is used.


    Rgds,
    Ramalakshmi.ch

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    what is the color significance of soldermask

    There is not much difference, its just a colour.

    Some like to keep main manufacturing boards Green yet prototypes red or Blue etc. But it makes no actual difference to the board.

    Your right about use of Black though, that is used when we don't want light reflections etc.
    Please do not PM me questions that are better asked in the PCB forum :)



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    Re: what is the color significance of soldermask

    I got some article about that, i don't know reality about that,

    * RoHS Compliant Low Halogen (HF) Solder Mask

    Having already selected a RoHS compliant base materials for the PWB, the designer must then consider selecting a solder mask material, a material that is also compliant as well as one that is compatible with fluxes and temperatures associated with lead-free solder processing. Since flame retardant chemistries are not actually added to the solder mask materials any halogens present in the coatings are introduced as ingredients or impurities. These halogens generally come from additives such as pigments used to create the color (green in particular) and/or by way of the residual catalysts from resin manufacturing. Pigments with lower halogen content are available for alternative colors (blue, red, black) but, during the transition to develop a material that can be classified as halogen-free (HF), any one of these less-traditional colors may be offered at a slightly higher cost than the more common green solder mask. Although the materials utilized in the manufacture of electronic products are usually required to have an Underwriters Laboratory (UL) Fire Retardant (FR) rating, the rating of the mask coating are really assessed after its applied to the substrate. This should not be a show stopper because, the solder mask coating is usually significantly thinner than the base laminate, the circuit board qualification relies upon the flame retardant element within the laminate to provide overall flammability protection for the finished substrate.

    In regard to solder mask color, the green tinted material has been a traditional preference for decades but, it contains a high

    level of chlorine.

    Chlorine is contained mainly at a molecular level in the “Green” pigment of all suppliers‟ masks; therefore, it is almost impossible to get a true green pigment that does not contain some level of chlorine. On the other hand, chlorine levels are not significantly relevant in colors like blue, yellow and red. This means that pretty much all non-green solder mask products can be classified as halogen-free and may explain why many products sold in the market do meet the HF definition are tented „blue‟ and have a very low and acceptable total halogen level.

    Solder mask products formulated with lower halogen content has not really affected the adhesion quality of solder mask materials and is expected to meet all established performance criteria. The most commonly referenced specification for solder masks is the IPC-SM-840, “Qualification and Performance Specification of Permanent Solder Mask”. Another source for evaluation of PCB circuit coatings is the Underwriters Laboratories Inc. Standard 94 (UL-94), “Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances.” These requirements are for all solder mask coatings regardless of their composition so they apply equally to halogen-free products. Furthermore, the basic properties of a HF version of a solder mask are not significantly different from solder mask materials that are not labeled specifically as „halogen free‟. Suppliers state that, “experience has shown little to no difference in fabrication processing parameters for a halogen-free solder mask compared to a non halogen-free (green) version of the same solder mask”. Any difference may be attributed to a possible change in pigment that could have a minor effect upon the exposure of a photo-imageable solder mask. This difference, however, would usually have minimal impact on the application process. Manufacturers typically have a wide selection of solder mask products readily available (liquid and dry-film) and note that nearly half of North American production utilized HF solder mask in 2008 because most of the current PWB products offered are also designated as RoHS compliant and qualify as halogen-free. When the polymer mask coating has been applied and cured, the board is made ready for the final surface finish process.



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