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June 27, 2017

Is Component Lead Damage Reparable?

Our lead forming process left gashes in the component leads. Some more than 10% of the lead thickness, some not quite.

Basis material was exposed on all leads that were sliced.

Do IPC standards allow the touch up of the exposed copper on component leads?

C.P.

Experts Comments

Maybe not the answer to the specific question (I don't know if the IPC standards allow for touch ups) but you may be able to prevent the damage so touch up is not needed.

In some leadforming dies, the corners can be sharp and the surfaces rough. These sharp corners and rough surfaces can cause the lead deformation.

Removing the die pieces and rounding the edges can reduce the nicks on the inside of the bends and the scrapes on the outside of the lead.

Additionally, highly polishing the areas of the die that contact the lead (or plating them) creates a smooth surface that will also reduce deformation.

In the old days, the acceptable "spec" was to not have exposed copper. Rounding the die and polishing will get you there most of the time.
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Marc Peo
President
Heller Industries Inc.
Mr. Peo has been with Heller Industries for over 20 years and has been President for the past 8 years. Marc has authored several industry articles on Soldering, Flux collection, nitrogen use and Lead Free conversion.
First I recommend you address the poor lead forming process that left gashes in the component leads. Goal should be zero percent damage to leads. As far as IPC standards allow the touch up of the exposed copper on component leads, I referred to my resident expert Janice Pobanz (IPC CIT & NASA Training Specialist ) and her input about J-STD-001:
  • Exposed basis metal shall not prevent the formation of an acceptable solder connection. 4.18.1
  • Different from a defect is a material nonconformance which, may not impact the appearance but may impact the performance/function of the hardware. See paragraph 1.5.2 Covering it up may hide a defect but will not change the fact that the diameter of the lead is not as required (more than 10%) and therefore may affect the performance/function of the component. This would lead to paragraph 3.8.1 which states that if the component is degraded below the part specification limits a documented analysis may need to be done to make that determination. Please see IPC-HDBK-001 paragraph 6.1.2 for addition comments on this issue.
  • The lead forming process shall not damage lead seals, welds, or connections internal to components.
  • Leads shall not be re-formed except for minor adjustments to bend angles.
  • Lead bending shall start no closer than 1 lead diameter or a minimum of 0.8 mm (0.031 in) to the package or lead-to-package weld.
Your strategy or comments to "touch-up exposed copper" we assume means filling in with solder. Hot solder dipping is only addressed in the standard to improve solderability not as a repair. We recommend that repairs should be approved by the "Customer" prior to the repair relative to the question of form, fit, function and reliability of the product for its intended use (what IPC class I, II, or III of product are we talking about). How expensive are these parts to not just replace them if they do not meet the standard? Key comment here "do not meet the standard".
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Mark Northrup
VP of Advanced Technical Operations
IEC Electronics
Mark has over 25 years' experience in electronics fabrication, quality and reliability while working for IEC Electronics, GE, Motorola, ORS, etc. He has most recently established Dynamic Research and Testing Laboratories, LLC now rebranded as IEC Electronics Analysis and Testing Laboratory, LLC in Albuquerque, NM for electronics and material analysis testing in the military, medical, and industrial industries. His area of expertise includes PCB, PCBA, components, analytical and electrical analysis techniques.
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