Rework, Repair or Modification

Introduction

In colloquial speech, we often use the word "repair" and mean the removal of nonconformities in the product. It does not matter what the scope of this repair is. Simply tightening a loose nut, replacing a defective component, or gluing a delaminated material - all of these are colloquially referred to as "repairs".

From a product quality perspective, however, there are some seemingly subtle but nonetheless important differences. Looking from the perspective of product quality, we can distinguish between two types of repairs:

• Restoring full compliance with the specification of the nonconforming product. Such a product is "as new". The manufacturer "sells it with the rest of the products" as new. Examples:
  • Tightening the nut.
  • Installing the missing screw.
  • Replacing an incorrect label.
  • Removing excess solder.
  • Replacing SMD components on a circuit board with the IPC-7711.
  • and many others..
• Restoring the functionality of the nonconforming product. The measures taken are aimed at bringing the product to function properly in its intended application. The repaired product is not 100% compliant with the specification, but will function properly. For example:
  • Surface grinding and additional application of paint coating.
  • Bonding damaged product components (instead of replacing or scrapping them).
  • Material surfacing.
  • Removing burnt PCB laminate and filling the cavity with epoxy resin.
  • Transplanting tracks or solder lands from a "donor" board.
  • and many others..

As you can see, the term repair can have multiple meanings and leads to many misunderstandings in the customer-supplier relationship. That's why the ISO-9000:2015 standard has made a very important and very valid distinction between these "types of repairs". Two terms have been defined:

Rework

Rework is an action that turns a non-conforming product into a conforming one[1]. Thus, it involves restoring full compliance with specifications, drawings, BoM, etc. A detailed definition is provided in ISO-9000:2015 par. 3.12.8.

Sometimes, a customer may prohibit the rework of the entire product or the rework of specific parts. It is also essential to ensure that the customer's definitions in such cases align with the manufacturer's definitions.

Rework usually includes adding a missing part, tightening a screw, removing excess material, or replacing components (soldering out the incorrect part and soldering in the correct one), etc.

Repair

Repair is an action that brings a non-conforming product to a state where it will be acceptable for a given application[1]. This means that a product after "repair" will not be 100% compliant with the specification, but it will be functional. A detailed definition can be found in ISO-9000:2015 par. 3.12.9.

Repair very often involves the introduction of non-routine materials that are not present in the standard manufacturing process. For example, additional surfacing of the material, addition of glue, additional wiring, extra weld, a second coat of paint, etc. The result will be a product that does not conform to the specification because, after all, the specification does not include additional glue, a second layer of coating, etc.

Rework in IATF-16949

The IATF-16949:2016 standard in paragraph 8.7.1.4 sets a number of requirements for the rework process. The main requirements are[2]:

• Perform a risk analysis, such as PFMEA, before implementing the rework process.
• If required by the customer, approval for rework shall be obtained.
• There shall be a documented process for confirming the rework (e.g., in a control plan).
• Instructions for performing rework shall be developed (and, of course, shall be followed).
• Records shall be retained (for traceability).

Repair in IATF-16949

IATF-16949:2016 in paragraph 8.7.1.5 defines requirements for the repair process, which are very similar to the requirements for rework, but there is an important difference. Customer authorization for repair is required, and it cannot be assumed that since the customer has not banned repair, it can be done[2].

IPC-7711 rework

The IPC organization has developed the IPC-7711 standard, which contains rules for performing "rework" and a set of procedures associated with each activity. The standard specifies how to remove varnish, desolder a component, clean solder lands, solder a new component and apply varnish[3].

IPC-7721 repair

The IPC-7721 standard is a document containing a set of repair procedures, which of course require customer authorization. The repairs in question are all sorts of rather complicated procedures, such as removing charred laminate and then applying resin, transplanting solder tracks and lands, and many others[3].

IPC-7721 modification

The IPC-7711/7721 standard uses the term "modification". It is used to describe changes made to an electronic product by replacing components, adding additional components, cutting tracks and soldering additional wires, etc. These activities are basically identical to those under "rework" and "repair", and looking at the process "from the outside" one would think that is the case.

The difference is that the rework and the repair refer to activities with a non-conforming product (i.e. one that does not meet the requirements received by the manufacturer), while the modification is related to making changes to a conforming product. Such changes are, for example, "upgrading / downgrading" a version of a product, changing a product to a different part number (a variant), correcting some design issues (which is not a manufacturing defect), etc.

Summary

The terms "rework" and "repair" have specific meanings in English and in quality standards (e.g. ISO-9001, IATF-61949, AS-9100, etc.). It is useful to use the appropriate nomenclature to avoid misunderstandings.

As a part of the customer-supplier relationship, it is important to remember that the repair always requires customer authorization, and the rework may require customer approval (but not necessarily..).

Note: Rework/repair can be a source of quality problems. In the electronics industry, a common situation is to correct acceptable conditions per IPC-A-610 to make them look like the target (ideal) condition. This is a costly and a harmful activity. Reworka nd repair are a risk in the soldering process. For example, flux, or rather "active flux residues" left behind can cause corrosion, formally referred to as electrochemical migration.

In the electronics industry, I would recommend using IPC-7711/7721. It is also worth remembering that other IPC standards also use the terms "rework" and "repair", which can be important factor in a customer-supplier business relationship.