This is my first Instructable. It is simple, cost me no money because I had the materials in my shop, and was quick. It worked so well I thought I would share.
After buying an aftermarket extended battery for my HTC Rezound cell phone I noticed that my reception was terrible. The battery was thicker than the original battery and came with a new back cover. I discovered that the circuits and contacts in the new back cover were just thinly applied copper colored paint. I inspected the original HTC back cover and saw that it also had conductive paint, but much thicker. This is how I improved on the cheap aftermarket back cover, resulting in greatly improved reception. The entire process took about 20 minutes.
Step 1: Materials
The only materials you will need:
About 4" of foil tape. I used aluminum because it was in my shop, but I suspect copper would be better.
A hobby or craft knife.
(not shown) a fine tip pen or marker. I used a Sharpie.
A pencil with an eraser.
Step 2: Make a Template.
On the inside of the back cover of your cell phone, cover the painted parts with transparent tape. Make sure the tape covers a larger area than the painted pattern. You will remove this later, so don't stick it too firmly. Two layers of tape will be easier to remove. Fold a corner of the tape back onto itself so you will have a tab to make removal easier. There will be some curved and some raised areas to cover, so you will need to carefully cut and/or add extra layers to some areas to make it fit smoothly. Take your time.
Using your marker, outline the painted areas on the tape. You don't have to be exact, just get the general pattern traced onto the tape.
Lay your foil tape flat, with the shiny side up. It will help to secure the edges with transparent tape so the foil tape won't slide around while you are cutting it.
Carefully remove the transparent tape from the back cover. You want to keep the pattern intact, so try not to tear the tape when you peel it off.
Stick the transparent tape, along with the outlined patterns, onto the foil tape. Make sure the pattern is flat, with no wrinkles.
Step 3: Cut the Foil.
Carefully cut along the outline of the pattern with your hobby knife. Use enough pressure to cut through the foil. You will need to hold down some of the smaller areas while you are cutting in order to prevent the foil from tearing. Foil tape is very thin and is easy to tear. The adhesive on the back of foil tape is not conductive, so your pattern needs to be one complete piece. If a piece tears, don't try to splice it back together. Just repeat the process and cut a new piece of foil.
You don't have to perfectly match the pattern painted on the back cover. Close is good enough.
Once your pattern is cut from the foil tape, remove the transparent tape you used as a template. Your hobby knife can be used to lift an edge and peel it off. This is the most difficult part of the process, because the foil tape will peel away from the backing. Just stick it back down and keep peeling the transparent tape.
Step 4: Apply the Foil.
Make sure the inside of the back cover is clean and dry. Remove the foil tape patterns from the backing and place them over the painted patterns on the back cover. Place the areas where the cell phone contacts the foil first. Those areas are usually raised, with flat surfaces for the contacts. Use the back of your hobby knife blade to gently push the foil into curves and recessed areas. Do not try to stretch the foil or it will tear. If the foil tears, start over. Use the blade of your hobby knife to place the foil strips. The adhesive on the foil sticks to skin much stronger than it sticks to metal.
Step 5: Finishing.
When you have placed the foil strips, use the hobby knife to trim any areas of foil that overlaps the edge of the back cover, or covers the attach points. Use a pencil eraser to smoothe the foil strips into curved areas, and to smoothe any wrinkles in the foil. Finally, use the eraser to clean the flat contact points.
The finished product will not look exactly like the original, but it will work just as good. Maybe better. When I first tried the aftermarket back cover I could barely get a signal in areas where the original back cover gave me four bars of 4G reception. My messy foil job now equals the reception of the original back cover. An unexpected bonus is that the phone seems to use less power with this modified back cover. The reason I purchased the extended life battery (3800 mAh) was because the original battery (1620 mAh) would die about halfway through my work day. I can now use the original battery with the foil enhanced back cover and get through an entire work day. The extended life battery will now last over 24 hours.