Question: What is the difference between touch-up, rework and repair?
Answer: According to IPC-T-50J – Terms and Definitions of Interconnecting and Packaging Electronic Circuits:
Touch-Up – the identification and elimination of defects in a product.
Rework – The act of reprocessing non-complying product, through the use of original or alternate equivalent processing, in a manner that assures compliance of the product with applicable drawings or specifications.
Repair – Action on a nonconforming product to make it conform to requirements. Unlike rework, repair can affect or change parts of the nonconforming product.
What does this all mean so I can understand it?
All of this begins with inspection of a product according to a specification, such as IPC-A-610, IPC-A-620, IPC-A-600, or J-STD-001 etc. Once the condition is found and identified and documented, the disposition can be scrap the unit, use the unit as is, or fix the unit. So, let’s say a component is in the wrong place or is not soldered correctly and it is fixed so that now you cannot tell the difference between a unit which was ok and the one that was fixed. This is called rework.
1. Example of Rework found in Section 6.1.4 of J-STD-001:
6.1.4 Lead Trimming Leads may be trimmed after soldering provided the cutters do not damage the component or solder connection due to physical shock. Tempered leads shall not [N1D2D3] be trimmed unless speciﬁed on the drawings. When lead cutting is performed after soldering, the solder terminations shall [N1D2D3] either be reﬂowed or visually inspected at 10X to ensure that the original solder connection has not been damaged (e.g., fractured) or deformed. 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 soldering process and not rework. This requirement does not apply to components that are designed such that a portion of the lead is intended to be removed after soldering (e.g., break-away tie bars).
The sentence which discusses the need to reflow the solder connection after cutting is considered part of the soldering process and it is not rework. In this particular case, the total operation of lead cutting into the solder fillet will need to be reflowed and this is considered Touch-up.
2. Example of Rework found in Section 4.7 of J-STD-001:
4.7 Rework of Nonsolderable Parts A component lead, termination, or board not conforming to the solderability requirements of 4.3 may be reworked (e.g., by dipping in hot solder) before soldering. A reworked part shall [D1D2D3] conform to the requirements of 4.3, less steam conditioning.
After the part is dipped in hot solder it will still look like the original part and the act of tinning the component again is a rework operation.
3. Example of Rework found in Section 10.1.4 of J-STD-001:
10.1.4 Rework of Conformal Coating Procedures which describe the removal and replacement of conformal coating shall [N1D2D3] be documented and available for review.
The process of removing and replacing, in this case conformal coating, is considered rework as the product will look the same as a new one when it is finished.
4. Example of Rework found in Section 12.1 of J-STD-001:
12.1 Rework Hardware defects shall [N1N2D3] be documented before rework. Rework for Classes 1 or 2 should and for Class 3 shall [N1N2D3] be documented. Rework includes hand solder touchup after mass soldering operations. Rework does not include a second application of a soldering iron during a hand soldering operation on a single connection. Proper soldering technique, including limiting the time on the connection and the amount of heat applied, is critical in pre-venting delamination or other damage to the assembly. Control of hand soldering shall [N1N2D3] include operator training, process controls, and management. See 1.10 personnel proﬁciency. Rework shall [D1D2D3] meet all applicable requirements of this standard.
This section again mentions touch-up after mass soldering operation and in this case, the physical process of touching up a solder joint is a Rework process.
Therefore, touch-up at times is part of the process and at other times it is part of the rework process.
Now, Repair from Section 12.2 of J-STD-001:
12.2 Repair A hardware defect shall not [N1D2D3] be repaired until the discrepancy has been documented. The repair method shall [N1D2D3] be determined by agreement between the manufacturer and the user.
As this statement indicates that the final product will not look like the original unit as signs of some work will be visible. An example of this would be a burnt hole in a board which has been fixed by removing the burnt area and refilling it with epoxy and such. This will be visible and this is considered a Repair process and it has to be approved by the customer prior to commencing the work.
Another example would be the fixing of a flat tire. Fixing a leak in a tire by putting a plug in the tire, or a patch on the tire is called repairing the tire, it doesn’t look like it did when it was brand new. On the other hand if the tire was low in pressure and air was added to the tire to bring it back to operational pressure, the act of putting air in the tires is call rework, because once the air is in the tire they will look like all the other tires with no visible sign of any changes in physically appearance.
Note: All J-STD-001 excerpts courtesy of the IPC and IPC J-STD-001 Requirements for Soldered Electrical and Electronic Assemblies.