We are experiencing poor wetting on various components placed on a PCB with En-Tek coating. Is anyone else experiencing simular problems ? We have the following questions:
1. How can the thickness of the En-tek coating be measured? 2. Is En-tek volume affected by the size of the pad? 3. Do you find that reflow profiles need to be adjusted with En-tek? 4. Is there an industry preferred solder paste that works well with En-tek coating?
| We are experiencing poor wetting on various components placed on a PCB with En-Tek coating. Is anyone else experiencing simular problems ? We have the following questions: | | 1. How can the thickness of the En-tek coating be measured? | 2. Is En-tek volume affected by the size of the pad? | 3. Do you find that reflow profiles need to be adjusted with En-tek? | 4. Is there an industry preferred solder paste that works well with En-tek coating? | | Any comments / suggestions are appreciated. | | Regards, | | Bill Tuttle | prod eng | Bill,
Welcome to the wonderful world of Entek. Great for screen printing; new rules for soldering.
We've found that it is possible to measure it optically by cross-sectioning the board. It shows up on micrographs at high mag if your sample is polished well. The volume can be affected by the application process. If it is applied in the horizontal, conveyorized system, it's nice & uniform. If it's applied in a dip tank, it will most likely be heavier on one side of a pad or an annular ring than the other, due to gravity.
As for solderability, most manufacturers now have fluxes designed to work well with organic solderability preservatives. If you're using an older model of paste, odds are that it's not being real cooperative. Call your paste supplier and tell them you're using Entek; they should be able to give you a drop in replacement for your current paste that will run with the same printing & reflow parameters.
Adjusting the reflow profile may offer minimal help, but you need a strong flux to activate through the Entek. If you're having problems soldering the second side of the board (either reflow or wave) checking the profile to make sure you're not spiking too high may help a little, but timing is everything. Get that second side soldered within five days! The Entek guys tell you you have at least seven days or more, but my experience with it (with my flux chemistries) says five.
If you plan on using a lot of Entek coated boards in the future, it is really worth revisiting your paste/flux chemistries. There is some really good stuff out there now that wasn't available two or three years ago. It's also worth checking into the board suppliers' application process. If you have any control over the fab house, try to get the horizontal process. I think its called the EPOCH process for "Entek Protectant Over Copper Horizontal" process. (that one was a stretch for the marketeers, huh?)