IC socket

As you know, conventional IC sockets have too much inductance to ever be used in modern switching power supplies. But, as I have said many times, it is just not enough to test one device/board and move on. We can have many boards made available to us, but they will probably last only for a few days. And besides, that also introduces too many variables in the initial stages of investigation. We would really like the flexibility of an IC socket that works. 

In Figure 9-7 and Figure 9-8, we have the answer to all our prayers. I used it for a 600mA Buck IC project recently with excellent results. Finding a vendor for this socket is very difficult. So I decided to share the contact info of the only person I know doing this. It seems to be a one-man show, and these sockets are custom-made on demand. But they have saved me months of evaluation time. Contact Weber at Rainbow Labs. Address 260 2nd Avenue, San Francisco, CA 94118, USA. Tel 415-387-4430, Fax 415-221-3640. No, I don t know them personally, and I have no commercial stake in their operations. The information is put out only to help you, since this sort of service is very rare. 

Be careful when using an IC puller. It is possible to remove the socket as well as the chip if you pull hard enough. You may also damage the motherboard permanently. 

Chip creep can affect any socketed device, including ICs, RAM chips, and expansion cards. The solution to chip creep is simple. Open the case and reseat the devices. It s surprising how often this is the solution to phantom problems of all sorts. 

Major polymer applications automotive lighting, ignition and braking systems, carburetor parts, fuel components, chip carriers, phone jacks, IC card connectors, transistor encapsulation, tape recorder head moimts, relay components, motor fans, coil bobbins, sockets, relay units, food choppers, steam hair drier parts, lamp sockets, microwave oven components, pump housings, impeller diffusers, oil well valves, halogen lamp sockets... 

Figure 4 shows an example of a pin grid array (PGA), developed to accommodate IC s with 84 or more pins. The original PGA s were ceramic packages, but several techniques are now used to produce them in plastic. The PGA s can be through-hole mounted on the printed wiring board, or can be socketed and surface mounted. 

The IC comparator is an extension of the logic test clip. The comparator allows the operation of an in-circuit IC to be compared against a known-good IC of the same type placed in the comparator s reference socket. While the circuit containing the IC under test is operating, the comparator matches the responses of the reference IC to the test device. 

The 386 is in the form of a "dual in-line package (DIP)." The black material is injection-molded epoxy polymer, with carbon black added to prevent random light from putting stray voltages on the PN junctions of the IC. Two lines of leadwires stick out of the bottom, like the legs on a centipede insect. It is difficult to attach clip leads to these, so a "breadboard" socket module will be used. This will provide useful experience for the experimenter, since these modules can be helpful in future circuit building. 

Each contact is interconnected through the molded substrate in some fashion, and the socket can be considered double-sided for interconnecting both the LGA IC and the PWB (see Fig. 50.5). 

FIGURE 50.5 Interposer sockets electrically connecting the PWB with an LGA IC (I) spring contact (r) Fuzz Button contact. 

Slow and even tightening is important to avoid damage to either the LGA IC device or the LGA socket and to ensure proper compression for reliable electrical contact. 

If soldered joints on the PCA need to be reworked in the vicinity of the LGA stack, use a thermal profile board, perform a mock repair, and measure the thermai effect on the socket. Ensure that the LGA IC and socket temperatures are maintained within their respective manufacturer s thermal guidelines. Also make certain that process chemicals, flux, cleaners, and such do not run under the LGA socket. 

ICs are sometimes connected into OIL sockets and at other times are soldered directly into the circuit. The testing of ICs is beyond the scope of a practising electrician, and when they are suspected of being faulty an identical or equivalent replacement should be connected into the circuit, ensuring that it is inserted the correct way round, which is indicated by the position of pin number 1 as described above. 

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