|A publication of the National Electronics Manufacturing Center of Excellence||
In April 2010 the IPC published a new revision of IPC-A-610: Acceptability of Electronic Assemblies with changes and additions that reflect the evolution of the electronics manufacturing industry. Some of the more significant changes will be described in this article, but the IPC has made available to the public a document that highlights each change from Revision D at the following web address: http://www.ipc.org/4.0_Knowledge/4.1_Standards/IPC-A-610E-redline-April-2010.pdf.
The first significant change to IPC-A-610 is the use of statements with the word shall to define requirements on materials and processes. This is a departure from previous revisions where IPC-A-610 limited the scope of the requirements presented to those that could be verified through visual inspection. An example of this new scheme includes the requirement that leads cut after soldering for Classes 2 and 3 "... shall be visually inspected at 10X to ensure the original solder connection has not been damaged ... [or] the solder connections may be reflowed."1 A new Class 3 requirement also specifies that leads must be reflowed (rather than inspected at 10X) if cut into the solder fillet.
Three new definitions were introduced with the new standard. Wire Overwrap (see Figure 6-1a) is defined as "[a] wire/lead that is wrapped more than 360° and remains in contact with the terminal post."2 Wire overwrap is acceptable for all classes for all wrap-type terminals. Wire Overwrap (see Figure 6-1b) is defined as "[a] wire/lead is wrapped more than 360° and crosses over itself, i.e., does not remain in contact with the terminal post."2 Wire overlap is typically considered acceptable for Class 1 but a defect for Classes 2 and 3 for wrap-type terminals. The final new definition is Nonfunctional Land, defined as "[a] land that is not connected electrically to the conductive pattern on its layer."2 A nonfunctional land is referenced in 4.3.2 (Press Fit Pins).
Chapter 5 (Soldering) saw changes to existing criteria in 5.2.11 (Lead Free Fillet Lift) and 5.2.12 (Lead Free Hot Tear/Shrink Hole). All defect conditions were removed from those two phenomena which in effect makes each acceptable as long as all other solder joint requirements are met and no impact on form, fit, function, or reliability can be expected.
The requirements found in 5.2.5 (Cold/Rosin Connections) were surprisingly missing from previous revisions on IPC-A-610. These conditions are now defined as defects for Classes 1, 2, and 3 when the condition prevents conformance to all applicable solder joint requirements.
Chapter 6 (Terminals) has been reorganized to increase the usability of the document. Each terminal type section (turret, bifurcated, slotted, etc.) now contains a table to summarize all wire or lead installation requirements and the installation and solder fillet requirements are now found together for each terminal type.
Chapter 7 (Through-Hole Technology) has received considerable attention in the new revision. Section 188.8.131.52 (Component Securing - Adhesive Bonding - Nonelevated Components) has been updated to reflect the requirements initially introduced in J-STD-001DS and carried over to J-STD-001E. A change was made to the Class 2 exception found in 184.108.40.206 (Supported Holes - Solder - Vertical Fill) which allows either 50% or 1.19 mm minimum vertical fill, whichever is less. As always, use of this exception requires that the plated through-hole in question is connected to a ground or thermal plane. Through-hole jumper wire requirements have been moved from Chapter 11 (Discrete Wiring) to the end of Chapter 7.
Requirements were introduced for soldering of daughter board subassemblies in 220.127.116.11 (Supported Holes - Board in Board). Requirements for Classes 1 and 2 are presented. Since no requirements have been established for Class 3, assemblies required to conform to Class 3 requirements must use the guidance found in 18.104.22.168 (Specialized Designs). This directs the manufacturer to use the existing requirements as guidance and recommends that unique acceptance criteria be developed in conjunction with the customer. "For Class 3 the criteria shall include agreed definition of product acceptance."3
Chapter 8 (Surface Mount Assemblies) has also seen significant changes, most notably to 8.3.12 (Surface Mount Area Array). This section has been updated to describe requirements for ball grid array (BGA) components with noncollapsing balls and column grid array (CGA) components. Section 22.214.171.124 explicitly adds head on pillow as a defect for Classes 1, 2, and 3. (See Head on Pillow Defects on BGA Assemblies from the March 2008 issue of Empfasis for further information regarding head on pillow.) New requirements have also been added in 126.96.36.199 (Surface Mount Area Array - Package on Package), which essentially repeat the standard requirements for BGAs with collapsing balls.
Section 8.3.13 (Bottom Termination Components) has been renamed to demonstrate that this section applies to a family of similar part types, rather than just to a single package type. Section 188.8.131.52 (Flattened Post Connections) has been added to reflect Class 1 and 2 requirements for this termination type (Figure 6-2). Finally, the jumper wire requirements specific to surface mount assemblies have been moved from Chapter 11 to the end of Chapter 8.
Chapter 9 (Component Damage) has been reorganized to incorporate damage requirements that were previously located in other areas of previous revisions of the standard. Examples of where damage criteria was moved from elsewhere in the standard are 9.8 (Connectors, Handles, Extractors, Latches), 9.9 (Edge Connector Pins), 9.10 (Press Fit Pins), 9.11 (Backplane Connector Pins), and 9.12 (Heat Sink Hardware). New damage criteria have been added in 9.6 (Relays) and 9.7 (Transformer Core Damage).
Chapter 10 (Printed Circuit Boards and Assemblies) has been updated to reflect the requirements originally found in IPC-A-610D Amendment 1 with regards to printed circuit board measling. New requirements are found in 10.2.3 (Laminate Conditions - Weave Texture/Weave Exposure) that defines "surface damage that cuts into laminate fibers"4 as a defect for Classes 2 and 3. Section 10.2.7 (Laminate Conditions - Depanelization) has been added to cover the common practice of routing or the use of breakaway tabs to separate single assemblies from multi-board panels. The requirements in 10.2.7 mimic the edge damage criteria from 10.2.4 (Laminate Conditions - Haloing and Edge Delamination). Section 10.5 (Marking) and 10.5.6 (Marking - Using Radio Frequency Identification (RFID) Tags) add information and requirements for the use of RFID tags on assemblies. Section 10.9 (Encapsulation) adds new requirements for the use of encapsulant materials which duplicate the requirements found in J-STD-001E.
The final obvious change to the standard is the formatting change to Chapter 12 (High Voltage). Although no changes to requirements are present, the chapter has been organized in a manner to increase the ease of use by presenting all target criteria on a single page, all acceptable criteria on a single page, and all defect criteria on a single page.
Certified IPC Trainer (CIT) certification is now available through the EMPF. Training materials for Certified IPC Specialist (CIS) certification are now available from the IPC. Contact the EMPF Registrar at 610.362.1200 or via email at email@example.com for further information regarding the availability of training to the new revision of IPC-A-610.
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