Peelable solder-stop, also known as peelable solder mask or blue mask protects selective areas on PCBs from wetting with tin by the solder wave during wave soldering (flow soldering). For this purpose, thermally curing peelable solder-stop is selectively applied to the areas to be protected.
Protected will be e.g. pads for a later, second soldering process as well as drill holes, gold or carbon contacts. After wave soldering, the peel-off solder-stop can simply be removed manually.
Production data: The layer with peelable solder-stop should always include the PCB outline. Please also specify whether the peelable solder-stop is required for TOP or BOTTOM.
Peelable solder-stop parameters
| Index | Blue Mask standard | Blue Mask special production | |
|---|---|---|---|
| Min. width | A | 0,6mm | 0,4mm |
| Min. overlap of copper | B | 0,6mm | 0,4mm |
| Min. distance to copper | C | 0,6mm | 0,4mm |
| Min. distance to PCB edge | D | 1,0mm | 1,0mm |
| Max. final hole diameter* | - | 1,9mm | 3,2mm |
| Max. width PTH-slit* | - | 1,6mm | 3,2mm |
| Typical thickness | - | 0,25 – 0,35mm | 0,2 – 0,3mm |
![[Translate to English:] Lötstopp abziehbar - Abziehlack](https://www.multi-circuit-boards.eu/fileadmin/img/03_Design-Hilfe/loetstoppmaske/abziehlack_blue-mask.png)
*larger parameters possible with polyimide tape, see below
Peelable solder-stop notes
- The layer with peelable solder-stop should always contain the PCB outline.
- Please specify if the peelable solder-stop is needed for TOP or BOTTOM.
- Avoid many small peelable solder-stop areas. Instead, connect small areas to form one large peel-off area. This also simplifies later removal.
If larger holes or slits are to be covered as well, additional peelable solder-stop is applied selectively by hand, thus the applied thickness is higher. Coarser design rules than those in the above table may then be necessary. Such additional effort can only be detected based on your production data.
If you foresee a special application of peelable solder-stop in your layout, we recommend that you include the production data with your inquiry. Contact our CAM.
Peelable solder-stop alternative: Polyimide/Kapton tape
For covering holes with a diameter ≥3.2mm ≤6.5mm, polyimide tape (Kapton or comparable e.g. 3M) is used instead of peelable solder-stop. In addition, polyimide tape can be used as an alternative to peel-off solder-stop when finer parameters are required.
Just like the peel-off solder-stop, the polyimide tape fulfils the protection from the solder wave tin and is selectively applied by hand. For non-critical areas, peelable solder-stop is typically still used for cost reasons. The thickness of the used tape is 50-125µm. Temperature Tolerance (short term) 260°C.
We will advise you based on your inquiry / production data should polyimide tape be required.
| Polyimide tape method | Polyimide tape cost factor | |
|---|---|---|
| Rough parameters | Tape cut and taped by hand | Higher than peelable mask, but most cost-effective method |
| Medium parameters | Tape cut by laser, taped by hand | Medium |
| Finer parameters as possible with peelable solder-stop | Tape pre-cut by hand, roughly glued to the PCB and exact contour cut by laser | High |
