Jeff,
I found prepreg on the manufacturer sites, but no where to actually buy it in small quantities. It makes sense because it is used in large sheets, not suitable for home use.
Harvey A.
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The material used to glue layers together in multilayer boards is called prepreg.\ufffd I don\ufffdt see prepreg sold online anywhere though.\ufffd Not even Ebay.\ufffd
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From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 7:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together\ufffd
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Brad,
I think you slipped a decimal point o the thickness of your boards- 0.031 and 0.0625".
There is another (better?) way, but it is problematical. You would get a much more uniform layer of adhesive by going with sheet adhesives. I my prior life, I was involved in some production that used sheet type adhesives to bond fairly big boards to heatsinks. The adhesive we used was an epoxy. I recall being able to buy sheet adhesives with or without a carrier layer, but since they were basically mixed, but uncured epoxy systems, they had to be kept in the freezer until use. The are other types of adhesives that also are available in sheet form. That was the good news. The bad news is that I couldn't find a place to buy these materials in reasonable quantities. I found an acrylic adhesive, recommended for this type of application, but it came on 3" rolls that were 250' long and 24" wide. Price was in the stratosphere. I looked at ebay, Amazon, McMaster-Carr and MSC to see if any of them carried these materials. Nada. A general Google search turned up some manufacturers, but no sellers at the retail level.
If you want to do your own search, look for sheet adhesives, adhesive preforms, bonding adhesive sheets.
If you should find a source, you will still be faced with the need to provide a fairly high, uniform pressure, and an elevated cure temperature. The material we used needed to withstand high temperatures, so we used something that cured over 150\ufffdC. Others are lower, but then it will depend on what you can find.
I did find some two sided adhesive mounting sheets at a craft store. No information available about what type of adhesive. They might work, but I am not so sure about how long they will stick, or if they might dry out.
Good luck in your search.
Harvey A.
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On 7/18/2017 11:14 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:
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So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I\ufffdm doing that replicates the 1973 TV Typewriter.\ufffd Except for one thing \ufffd the stock is 0.31\ufffd thick, rather than 0.625\ufffd.\ufffd So my thought was to epoxy two pieces together.\ufffd And that works, except despite my best efforts, I end up with these ugly voids you can see.\ufffd I\ufffdve tried putting the boards under a press with heavy pressure but there\ufffds always a few spots.
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Is there a better way/adhesive to do this?\ufffd
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I realize it\ufffdd be easier to use 0.625\ufffd stock from the outset, but stock of the correct vintage just isn\ufffdt available, and it means a lot of me to be using actual boards from the time.
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Thanks!!
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