Through-hole plating double-sided PCBs

Published:2011/7/26 21:06:00 Author:Phyllis From:SeekIC

Making a double-sided PCB is far from easy. It is quite a task to make sure that the artwork films with the tracks and pads are perfectly aligned on both sides. And it becomes even more difficult when both sides have to be connected at various points.

The professional PCB manufacturer uses through-hole plating: the board is drilled and a thin layer of copper is deposited in the holes that require a connection between the top and bottom side. An electrochemical process is then used to make the actual connection. This however requires specialist equipment, which won’t be available in many electronics labs. Fortunately there are other methods, although they are somewhat laborious. These methods are also useful when repairing damaged double-sided boards.

The simplest solution is to solder the pins or leads of the components on both sides of the board. This is easily accomplished with conventional components (resistors, diodes, transistors, etc.), but with radial capacitors and ICs (in sockets) this is more difficult. The second method uses Lilz wire, which is often on hand in the electronics workshop. This wire consists of many thin copper strands, which are highly suitable For making connections between two sides of the board and still leave enough room in the holes for the component leads (Figure 3). The thin strands are soldered on the component side of the board, taking care that the solder joint doesn’t rise above the board too much, and that the hole doesn’t become blocked by the solder. When all connections have been made, the components can be placed on the board and soldered on the solder-side. We recommend that you use two strands per connection, thereby reducing the risk that a connection is damaged when the component pin is stuck through the board.






For DIL-IC sockets there is a much simpler method: there are contact strips that have the same type of contacts as turned-pin IC sockets. These have the advantage that they are raised slightly further above the board, providing enough room to solder the pins on both sides of the board (Figure 4). These strips are preferable to ordinary turned-pin sockets because the pins on the component side of the board are easier to get to with a soldering iron from both sides.

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