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kapton dots and liquid solder mask

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pr

#35997

kapton dots and liquid solder mask | 9 August, 2005

We have some large plated through holes, that we protect with hand placed Kapton dots before they go into the wave. Is there a better option? We are going to see if the boardhouse can put them on for us but I was curious how others are/would do this.

thanks, pr

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SuMoTe

#35999

kapton dots and liquid solder mask | 9 August, 2005

Water soluable dots will wash off after reflow. A water soluable liquid mask will work as well. dots are better for defined (round)holes, whereas the liquid mask works well with odd shapes.

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Rob

#36002

kapton dots and liquid solder mask | 9 August, 2005

We sometimes use a peelable mask the the PCB manufacturer (board house) adds as part of their process. It may seem an expensive option but avoids:

Raising P/o's for tape/peelable mask as consumables booking & inspection Booking out to the shop floor Labour in adding to the board stock checks accounts paying the supplier Running out without realising....

etc.

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#36005

kapton dots and liquid solder mask | 9 August, 2005

Why are you placing Kapton dots on your board prior to wave soldering? * Prevent solder from touching the hole and the area around it. [If so, why do you need to do this?] * Prevent solder from flowing up through the hole and coating portions of the board a shiny silver color.

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pr

#36013

kapton dots and liquid solder mask | 9 August, 2005

From what I can gather, the annular rings are used for grounding when these boards are put in housings. A screw goes through the hole and is torqued down. If there is excess solder on the annular ring, the screw doesn't seat properly. The pallets cover some holes but we mask up to 6 holes on some jobs, time consuming and costly. These are densly populated..............You got me thinking! I will look into double reflow on these and spot solder the big honkin connectors. I am still up for possible alternatives for Kapton (just in case the powers that be don't like my double reflow idea).

Thanks for any and all input, pr

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#36017

kapton dots and liquid solder mask | 9 August, 2005

You can also insert a stainless steel screw the size of the hole in the board before wave soldering, this will prevent the solder from wicking up to the top or close the hole (this is real cheap). I still remember the good old days using toothpicks to prevent holes being closed during wave soldering.

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#36025

kapton dots and liquid solder mask | 9 August, 2005

Since these are mounting holes, they're probably all the same size. Why not try rubber plugs shaped like golf tees?

Try: * Dempsey Industries; 802 N. 4th St, Miamisburg, Ohio 45342; (937)-866-2345; Gary Pascoe * Shercon somewhere in CA * Harman; 360 South St. Rochester, MI; 810-651-4477 * StockCap St Louis MO 800-827-2277 * MOCAP Plastic Products Group; 10964 Lin-Valle Drive, St. Louis, MO 63123; 800-633-6775 314-845-3100 Fax 487-8855 http://www.mocapinc.thomasregister.com/olc/mocapinc/

* Kinnarney Rubber; 450 Main St PO Box 37 Mantua, NJ 08051; 856-468-1320 FAX 7438 jimk@kinnarney.com

* Caplugs Protective Industries [ESD dissapative]; LLC 2150 Elmwood Ave Buffalo, NY; 888-227-5847 http://www.caplugs.com/

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pr

#36041

kapton dots and liquid solder mask | 10 August, 2005

Is the peelable mask (put on by the boardhouse) flat on the surface of the pcb? If so can you tell me the material name, so maybe I can find a picture? We have to print adhesive on the board, so the mask has to be flat. That is why Kapton from the boardhouse is the best option so far. We can't use spot solder because there are 44 TO-220s on the edge and 20 or 30 axial parts, so it would be too slow to spot solder (with double sided reflow). we run these in lots of 1000 - 1500 so having operator's do it is killing us.

thanks for the help, pr

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Rob

#36043

kapton dots and liquid solder mask | 10 August, 2005

Hi Pr,

No idea what the material is - we haven't usd it for a while now, but it was flush & didn't cause any printing problems on double sided reflow. Your board house should know all about it - I would suggest some but ours are all UK or China/Taiwan.

BR, Rob.

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pr

#36050

kapton dots and liquid solder mask | 10 August, 2005

O.K. thanks, I'll look into it............through a rep, since all our boardhouses are in China/Taiwan. I'm seeing a pattern!

thanks, pr

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#36171

kapton dots and liquid solder mask | 18 August, 2005

We have our board house apply a peel coat mask that can be brushed off after wave or reflow. You need to brush off while it's still warm.

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