There are sockets available for both DIP packages and SMD packages. No matter which direction you take, I would suggest using a socket. That way, if you let the smoke out, replacing the chip doesn't require desoldering and resoldering.
The choice between DIP and SMD is all about what you are more comfortable with. There is typically a larger variety of microcontrollers available in SMD. But they are also more fragile. Especially when used with a socket. If you're taking the chip in and out a lot, you will most likely bend or break some pins. The pins on a DIP are much more forgiving in this respect.
It's rare that you'll find someone taking a chip out of circuit and placing it in an off-board programmer these days. I had to do it with old school PROMs in college. But I haven't done it since. You are much better off having the JTAG on the board itself. @i.amniels mentioned in-circuit debugging being a huge advantage. I will echo that sentiment as it cannot be said enough.
There are many different JTAG connector configurations. The AVR one uses 10 pins. And you really don't have a lot of say in the footprint of the header you can choose. You have to match the pin size and pitch to your JTAGICE. Atmel has a recommendation for the part number to use to interface to the JTAGICE. I would just stick with that.
http://support.atmel.com/bin/customer.exe?=&action=viewKbEntry&id=2
The typical thing to do on Cortex parts that only have a single processor core is to only use SWD. In this case, the only lines which need to be routed to the 10-pin header are SWDCLK/SWDIO/SWO/!RESET/+3V3/GND. Notice that !RESET is the microcontroller reset, and is not the same as TRST. From my experience, the only pin that needs to be pulled up via a resistor is !RESET, at least using a Ulink2/Ulink ME debug adapter. On most Cortex processors, the JTAG and SWD lines are actually shared, for example, SWO is the same pin as TDO, but that appears to not be the case here. If your tools support both JTAG and SWD, you can pick the system which conflicts the least with your other peripheral/pinning needs. If you must share the debug pins with other hardware, then the ISP pin should be pulled up and wired to one of the GND pins on the 10 pin connector (the GND pins are internally shorted on the debug adapter so that it will pull down when the debugger is connected, allowing you to enter ISP mode).
In general, SWD requires fewer pins, and can use SWV (Serial Wire Viewer) which gives you printf redirection and other features, while JTAG allows for chaining (and access to both cores on dual core parts such as the LPC4300), and is the only option for older tools.
The part number for the shrouded connector is FTSH-105-01-F-D-K, but in practice it is difficult to find, but you can probably put out a RFQ on Alibaba or a similar B2B site.
Best Answer
That small green board likely just contains a surface-mounted pin header style shrouded connector on it's bottom side (hidden) that is connected to the mating connector on the cell phone's motherboard. That connector exposes the JTAG signals.
Here is another example:
The JTAG port is circled in red and enlarged in inset. This motherboard is missing the connector on the motherboard side, so that green adapter PCB wouldn't be necessary. Instead, you would have to solder ("weld" in your terminology) high gauge wires to the exposed pads on the PCB like in your photo between the green adapter PCB and the larger adapter PCB.
That second PCB is yet another adapter that goes from the bare soldered wires into a connector that is compatible with the JTAG interrogator unit (visible in the background with the blue LED).