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WonderMASK W Washable Solder Mask
Temporary solder mask is intended to be just that – temporary. Manufacturers of solder masks, like Chemtronics, always recommend removing the mask because there is no testing to support doing otherwise. If you decide to leave the solder mask on as a permanent part of the PCB, you will have to do your own functional and reliability testing to ensure it does not cause a problem.
Particulates + surfactants during rinse = foam. Check filtration system or drain & recharge the rinse water system as necessary. The particulates may come from various sources, but excess solder flux being rinsed off the boards is a prime culprit. Bacteria in the water can cause foaming. Have a water sample analyzed.
Solder mask is engineered to withstand molten solder temperature for the very brief time (about a second) it is exposed in a typical wave soldering process. Most commercially available masks should be able to withstand melting point temperatures of lead-based and lead-free solder, up to 650°F (343°C). As exposure time is lengthened, like in a reflow oven, there is more potential the mask will bubble, char, and become brittle. How long a mask can withstand extreme temperatures depends on the thickness of the bead, and the type of mask.
No, temporary solder mask will not leave behind ionic residue that can lead to dendritic grown and board failure.
Washable mask is engineered to be removed in an aqueous inline or batch wash system. If you are using a closed-loop system, which filters and recirculates wash water, make sure you use a mask that is compatible with your physical filters and ion beds. If you experience foaming, it is an indication that either too much mask material is being passed back into your cleaning system or it is interacting with dissolved flux in the same wash water. This is generally solved by replacing your wash water with fresh DI water, but a defoaming agent can be added as a stopgap solution.
Spot mask can be hand applied, dispensed with a pneumatic system, or stencil printed. To hand apply using a squeeze dispensing bottle: 1) hold the mask bottle upright, but at an angle (around 60°), 2) squeeze the bottle as you drag is across the areas to be masked, 3) for best results, allow mask to fully cure before running through extreme soldering temperature.
The shelf life of a product can be found on either the technical data sheet (TDS), available on the product page, or by looking on the certificate on conformance (COC). The COC can be downloaded by going to https://www.techspray.com/coc. Once you have the shelf life, you will need to add it to the manufacture date for a use-by date. The manufacture date can be identified by the batch number. The batch code used on most of our products are manufacture dates in the Julian Date format. The format is YYDDD, where YY = year, DDD = day. For example, 19200 translates to the 200th day of 2019, or July 19, 2019. This webpage explains and provides charts to help interpret our batch numbers: https://www.techspray.com/batch-codes.
The follow are factor to consider when trying to avoid breakage: 1) Curing – Partially cured mask will have more of a tendency to break or leave residue. 2) Temperature and duration in extreme heat – Mask is designed for wave soldering, which is about a second of exposure to molten solder temperatures (generally 550°-650°F). If the mask is sent through a reflow oven the duration is much longer, which can lead to more mask brittleness. If the mask is exposed to high-temperature solder (e.g. silver), it can also lead to more brittleness. 3) Application method – When hand applying, we recommend holding the bottle at about a 60° angle, rather than upright at 90°. That tends to apply the material as a thick blanket over the areas to be masked. When the bottle is held at 90°, the mask is generally applied thinner, and is forced through holes and around components. Those thin areas are more likely to become brittle and stay behind, and mask pushed into holes and around components is harder to remove, so more likely to break.