Establishes the requirements for the evaluation of liquid and dry film solder mask material and for the determination of the acceptability of use on a standard printed board system. IPC-SM-840 provides two classes of requirements, T and H, to reﬂect functional performance requirements and testing severity based on industry/end use requirements. Coverage is given to adhesion, material qualification, resistances to solvents, and electrical requirements. Revision D incorporates resistance requirements to lead free soldering processes. 16 pages. Released April 2007. Preview the table of contents .pdf file.
Establishes the requirements for the evaluation of liquid and dry film solder mask material and for the determination of the acceptability of use on a standard printed board system. IPC-SM-840 provides two classes of requirements, T and H, to reﬂect functional performance requirements and testing severity based on industry/end use requirements. Coverage is given to adhesion, material qualification, resistances to solvents, and electrical requirements. Revision E incorporates requirements for flexible cover materials used as a flexible dielectric protective layer over etched conductors and other conductive features.19 pages. Released December 2010.
6 IPC-SM-840D April PREPARATION OF SOLDER MASK MATERIAL FOR DELIVERY Preservation, Packaging and Packing NOTES Specifying Solder Mask on Printed Boards Special Requirements Figures Figure 4-1 IPC-B-25A (Note: No solder mask shall be applied to contact fingers) Figure 4-2 IPC-2221 Test Coupon E Layer 1 ( Y Configuration) Tables Table 3-1 Requirements of Qualification... 4 Table 3-2 Adhesion to Rigid Printed Boards (IPC-B-25A Test Board and/or Production Printed Board)... 6 Table 3-3 Moisture & Insulation Resistance... 8 Table 3-4 Electrochemical Migration... 8 Table 3-5 Thermal Shock Conditions... 8 Table 4-1 Sample Requirements/Suggested Test Sequence for Table 3-1, Column A IPC-B-25A Standard Test Boards... 9 Table 4-2 Sample Requirements/Suggested Test Sequence for Table 3-1, Column B IPC-B-25A Boards - Production Process or Conformance Coupons or Production Printed Boards iv
7 April 2007 IPC-SM-840D Qualification and Performance Specification of Permanent Solder Mask 1 SCOPE AND DESIGNATION 1.1 Scope This specification shall define the criteria for and method of obtaining the maximum information about and confidence in cured permanent solder mask material under evaluation with the minimum of test redundancy. This specification shall establish the requirements for: The evaluation of solder mask materials. The conformance of solder mask material properties. The qualification of the solder mask via the appropriate test substrate. The qualification assessment of the solder mask in conjunction with the production printed board process. 1.2 Purpose This specification shall establish the requirements, based on applicable test methods and conditions, for the evaluation of a solder mask material and for the determination of the acceptability of use on a standard printed board system. These same requirements shall also be used to qualify a printed board production process based on conformance criteria defined by the reliability requirements of the end use environment. Acceptability and/or verification criteria of the production printed board shall be determined in accordance with the applicable performance requirements contained in IPC-6011, IPC-6012, IPC-6013 and IPC The solder mask materials described herein, when applied to the printed board substrate shall prevent and/or minimize the formation and adherence of solder balls, solder bridging, solder build-up and physical damage to the printed board substrate. The solder mask material shall help retard electromigration and other forms of detrimental or conductive growth. NOTE: The determination of compatibility between solder mask materials and post soldering products and processes is beyond the scope of this specification. The use of Test Methods specified herein to determine the compatibility and the requirement to do so shall be as agreed between user and supplier (AABUS). This specification shall list the base requirements for solder mask and solder mask production processes. The solder mask shall be cured per the manufacturer s recommended process in accordance with those conditions specified for that product. Additional requirements or deviations from these requirements shall be AABUS. 1.3 Classes This specification provides two classes of requirements, T and H, to reflect functional performance requirements and testing severity based on industry/end use requirements. Qualification to a particular class shall not be extended to cover any other class. Note: The reference of a single class does not preclude invoking or allowing specific requirements defined in other classes. T Telecommunication This includes computers, telecommunication equipment, sophisticated business machines, instruments, and certain noncritical military applications. Solder mask on printed boards in this class is suitable for high performance commercial and industrial products in which extended performance life is required but for which interrupted service is not life threatening. H High Reliability/Military This includes that equipment where continued performance is critical, equipment down-time cannot be tolerated and/or the equipment is a life support item. Solder mask on printed boards of this class is suitable for applications where high levels of assurance are required and uninterrupted service is essential. Notes: Class Designations Previous versions of this and other IPC specifications make reference to Class 1, Class 2, and Class 3 end product classes. For all practical purposes there is no Class 1 solder mask. The requirements in this specification are not applicable for solder mask used in Class 1 end-product. Class 2 is equivalent to Class T (Telecommunications). Class 3 is the equivalent of Class H (Military/high reliability). Solder mask types were previously described as Type A for screen imaged (liquid) or coverlay for flex (dry), and type B for all types of photo defined solder mask (liquid or dry film). A Type B1 solder mask was identified as a liquid solder mask and a Type B2 solder mask was identified as a dry film solder mask. 1.4 Presentation Dimensions and tolerances shall be expressed in metric units. English units are shown in brackets [ ] and are not necessarily direct conversions or usable numbers. Reference information is shown in parentheses ( ). Deviations to this shall be AABUS. 1.5 Terms and Definitions The definition of terms shall be in accordance with IPC-T-50 and as stated in through
8 IPC-SM-840D April AABUS This is an acronym for as agreed between user and supplier. Indicates additional or alternate requirements to be decided between the user and the supplier in the procurement documentation. Examples include contractual requirements, modifications to purchase documentation, and information on the drawing. Agreements can be used to define test methods, conditions, frequencies, categories or acceptance criteria within a test, if not already established. For reference in this specification, the manufacturer of the solder mask material is the supplier. The fabricator of the printed board with the solder mask applied is the user, unless within the context, the fabricator is supplying it to the end user, then the fabricator is the supplier Blistering Delamination in the form of localized swelling and separation between any of the layers of a lamination base material, or between base material and conductive foil, or protective coating, or solder mask Chalking (Cured Solder Mask) When the solder mask is degraded such that fine particulates can be removed from the surface Color Change (Cured Solder Mask) Any change from the original color after the solder mask has been cured and the legend and final finish have been applied CoC This is an acronym for Certificate of Compliance Crazing (Conformal or Solder Mask Coating) A network of fine cracks on the surface of or within the coating Delamination (Cured Solder Mask) A separation between plies within a base material, between a base material and a conductive foil, or any other planar separation within a printed board FTIR This is an acronym for Fourier Transform Infra-Red (Spectroscopy) Liquefaction (Cured Solder Mask) When cured (solid) solder mask becomes partially to fully liquefied Peeling (Cured Solder Mask) The loss of a portion of the solder mask from the printed board resulting from a lack of adhesion Softening (Cured Solder Mask) A decrease in hardness as evidenced by a decrease in pencil (scratch) hardness test results Solder Mask For the purposes of this specification, the term solder mask shall refer to any type of permanent polymer coating material applied prior to assembly, but excluding marking (legend) inks and hole plugging materials Swelling (Cured Solder Mask) An increase in volume, noted as an increase in solder mask thickness due to absorption of another material such as a solvent Tackiness A condition where a material or a surface will become degraded so as to become sticky, slightly adhesive, or gummy to the touch Wicking (Solder Mask) A condition where wet solder mask on the surface of a panel is drawn into the holes (via, mounting or component). 2 APPLICABLE DOCUMENTS The revision level of the following specifications, in effect at the time of order, form a part of this specification to the extent specified herein. 2.1 IPC 1 IPC-A-25A-G-KIT Multipurpose 1 Sided Test Pattern 2 IPC-T-50 Terms and Definitions for Interconnecting and Packaging Electronic Circuits J-STD-003 J-STD-004 Solderability Tests for Printed Boards Requirements for Soldering Fluxes J-STD-006 Requirements for Electronic Grade Solder Alloys and Fluxed and Non-Fluxed Solid Solders for Electronic Soldering Applications IPC-2221 IPC-6011 Boards Generic Standard on Printed Board Design Generic Performance Specification for Printed IPC-6012 Qualification and Performance Specification for Rigid Printed Boards IPC-6013 Qualification and Performance Specification for Flexible Printed Boards SAC 305 A solder alloy/paste comprised of 96.5% Tin, 3% silver and 0.5% copper. IPC-6018 Test Microwave End Product Board Inspection and This product contains the electronic Gerber artwork files necessary for generating the IPC-B-25A test board. 2 2b1af7f3a8