Circuitboard construction

[Robert Reed]

I need to install a 50 ohm strip line on the resin side of a single clad circuit board. This piece of foil will be approximately 3" long and 1/8" wide and ultimately sectioned off for SMD components. I have never attempted a glue down line and wondering if there is any suitable adhesive that can stand up to a soldering pencil heat. And while I'm on the subject, how do they get the normal cladding on circuit boards to adhere so tightly.

[Externet]

Hi.
The glue used for layering boards is good, but never bothered to search on PCB manufacturers supplies. Has to be near cyanocrylate/epoxy.

Suggest to drill a hole each side of the RG174U ? and secure down with a tiny nylon tie.
Miguel

Learned something today... ----> https://duckduckgo.com/?q=prepreg++glue&t=canonical

[Lenp]

Hi,
See if this helps http://www.rogerscorp.com/acm/productty ... epreg.aspx

[haklesup]

Copper is bonded onto the core through a multi step chemical process ending with electrolessplating. Only in the context of PCB repair would one try to glue a trace down, normally to do what you want one would use a double sided board and etch the stripline.

However, you should be able to use self adhesive copper tape or almost any stable and thin adhesive and then over layer with a conformal coat or smear of mixed epoxy. Note that whether you try glue or adhesive, you will have difficulty controlling the impedance because the dielectric thickness will be inconsistent but maybe good enough for your application. I suppose the clad side you are using as the ground plane. The thickness of the board will play into the calculations you need to make 50 ohms impedance.

I would probably use 5 min epoxy smeared on the board then squeegee the trace after you place it to make sure it is consistent thickness and as thin as possible (after all, it ends up being part of the dielectric and possibly screwing up your impedance calculations). After that cures, I would go over the top with more epoxy to make a sort of soldermask. I like Epoxy because it will not break down if you try to clean with alcohol or acetone later.

You can mask areas for soldermask openings for your components by using Silicone RTV before you do the final epoxy coat. this will be soft enough to peel off after the epoxy cures revealing clean copper you can solder to. Just use a light touch with the solder iron and you should be fine, use 60/40 solder for the best performance

[Lenp]

Copper foil of various widths is used in stained glass work. A craft shop might be a place to start!

[Robert Reed]

Thanx for the replys fellows. In reading thru all the threads, I am now a little reluctant to try glue products. The overall board is only2.5" by 3.0", so I may just stick with double sided board and grind away one side to all but the strip desired. There will be 8 SMD components to solder in and all in line, so there will be considerable heating along its length. The upside is I will be working with original bonding quality- the flip side is trying to maintain the exact width for a 50 ohm transmission line end to end. I will probably need a few practice pieces before I can get the machining setup perfected. I also think I will play around with a few scraps with glued on foil strips, more out of curiosity than method of final construction.