Question: I’m having trouble discerning the requirements for post lead trimming reflow in the new version of IPC-A-610. It seems to indicate only “leads must be covered by solder”. Can you elaborate on where I may find more conclusive instructions in the 610 to share with operators?
Answer: This following information is from Rev D of IPC-A-610. The requirement was to inspect all joints after cutting and make a determination as to whether or not the connection was damaged, then if damage was found, the solder joint was to be reflowed. The inspection was to be completed at 10x magnification. The caveat was that if one did not want to inspect the joints, they simply could be reflowed and that took care of the requirement.
This is From 610 Rev E Section 188.8.131.52 Lead Cutting After Soldering. It is the same criteria as written in the Revision D versions.
The following criteria apply to printed board assemblies where the connections have been trimmed after soldering. Leads may be trimmed after soldering provided the cutters do not damage the component or solder connection due to physical shock. For Classes 2 and 3, when lead cutting is performed after soldering, the solder terminations shall be visually inspected at 10X to ensure that the original solder connection has not been damaged, i.e., fractured or deformed. As an alternative to visual inspection, the solder connections may be reflowed. If the solder connection is reflowed this is considered part of the soldering process and is not to be considered rework. This requirement is not intended to apply to
components that are designed such that a portion of the lead is intended to be removed after soldering, i.e., break away tie bars.
The requirement as defined by Class 3, is when the solder joint is cut into such as the illustration on the left, it must be reflowed regardless of whether or not it was inspected at 10x. Therefore any cut into the solder joint fillet during lead trimming the solder joint must be reflowed.
This is also defined in J-STD-001 in paragraph 6.1.4 Lead Trimming, where it states: … Lead trimming after soldering that cuts into solder fillets shall [N1N2D3] be reflowed Figure (6-2). If the solder connection is reflowed, this is considered part of the solder process and not rework. Figure 7-112 is the same figure 6-2 of IPC, J-STD-001 page 21.
Therefore all documents agree on how this condition is to be addressed.
There are no requirement in this section where the leads must be covered with solder.
The only place that addresses where a lead be covered with solder is in J-STD-001 ES, section 4.18.1 Exposed Surfaces, where it states,
· Ends of leads or vertical edges of lands is acceptable except:
- Iron based, e.g. Alloy 42, Kovar, component leads, body shall not be exposed.
- Exposed basis metal shall not prevent the formation of an acceptable solder connection
- Exposed Organic Solderability Preservatives (OSP) shall not prevent the formation of an acceptable solder connection.
I hope this answers your question .
(All images and quotes are from associated IPC Industry Standards.)