Soldering a socket on your board

Mainboards where the BIOS chip is soldered onto the board (i.e., not in a socket) are usually problematic for coreboot developers and especially coreboot users, as one incorrectly flashed image will render the board unusable.

Here's a simple procedure how you can desolder/remove the chip from such a board, and solder on a PLCC socket instead (so that you can swap chips as often as you like later on).

Important: This will definitely void the warranty of your board! Also, we take no responsibility for any damage you inflict on your board or other stuff. Use at your own risk!

That said, we believe this procedure requires only relatively low-cost equipment which is widely available, and can also be performed by people without much soldering experience. You do not have to be a hardware/soldering guru to do any of this, with a little practice everyone can learn to perform the procedure.

Requirements

• A board with soldered-on PLCC chip (a similar procedure will likely work for DIP32 or DIP8 chips).
• A soldering iron, solder, and soldering wick.
  • Optional: No Clean Flux ("Flussmitteldispenser" in German) for easier soldering.
• A PLCC socket (SMD type).
• A desoldering station / heat gun (or a cutter).
  • Optional: Vacuum suction pen for holding/dragging the chip
• Tweezers.
• Pliers.

• 

  Soldered PLCC chip

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  Soldering iron

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  Solder

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  Desoldering wick

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  PLCC socket, front

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  PLCC socket, back

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  Cheap desoldering station

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  Desoldering accessories

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  Tweezers

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  Pliers

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  No Clean Flux

The desoldering station used here is an Aoyue 852 SMD Rework Station, which is available relatively cheaply (ca. 70.- Euros). There are even cheapers ones available, e.g. on eBay.

Preparation

• Take a picture of the board and ROM chip. You might need that later in order to add the socket in the correct orientation. The ROM chips all have a marking where the top is (and the same is true for most boards), but on some boards there is no such marking. So write down the orientation of the chip (or take a picture).
• Prepare the PLCC socket, by cutting away the plastic middle part using the pliers (for easier soldering later):

• 

  Pliers and PLCC socket

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  Cut the middle part

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  Socket and removed plastic

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  Prepared socket, back side

Desolder or cut away the ROM chip

The next step is to remove the soldered ROM chip. There are basically two ways to do that.

• Desoldering the chip.
  If you have access to a desoldering station use that for desoldering the chip. Use a temperature of ca. 350-370°C. Higher temperatures might speed up the process a bit, but will also increase the risk of damaging the chip or surrounding parts. At 370°C the process takes less than 20 seconds.
  • Advantages:
    • Quick and painless method.
    • The ROM chip will usually survive, if you're careful and don't supply too much heat.
  • Disadvantages:
    • You have to spend some money on a desoldering station (less than 70,- Euros).
    • The surrounding chips, resistors, etc. might get too hot if you're not careful (usually doesn't happen, though).
• Cutting the chip.
  Alternatively, you can just cut away the chip with a proper cutter (e.g. the Hakko CHP Ergonomic Micro Cutter).
  • Advantages:
    • No desoldering station required.
    • Surrounding chips, capacitors, etc. are not at risk.
  • Disadvantages:
    • Cutting the chip is a bit tedious.
    • The chip is rendered unusable in the process (so make sure you have a backup before cutting it).

• 

  Soldered PLCC chip

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  Desoldering temperature

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  Hold the chip with tweezers

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  Desoldering the chip

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  PCB pads after desoldering

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  Desoldered chip, front

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  Desoldered chip, back

Clean the pads on the board

The next step is to clean the PCB pads, i.e., remove the remains of solder from the pads. Use desoldering wick for that.

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  Pads before cleaning

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  Cleaning with desoldering wick

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  Cleaned pads

Solder the socket onto the board

Now solder the PLCC socket onto the pads. This procedure is best performed manually with a soldering iron (in theory you could try to use a desoldering station / heat gut, but the results are probably not too good, and you might melt the plastic socket). Optionally, if you have some No Clean Flux handy, apply some of it on the pads. This will make the soldering process a bit easier.

We suggest to start by aligning the socket onto the pads with tweezers or with your fingers. Solder two pins in opposite corners of the socket first, in order to fixate the socket. Then solder all the other pins, one after the other. If you apply too much solder and two or more pins get connected accidentally, use the soldering wick to fix that.

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  Put solder on a pad

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  Put solder on another pad

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  Aligning, tweezers

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  Aligning, fingers

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  Soldering the socket

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  Soldered-on socket

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  Testing the socket

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  Socket with chip

Results

Congratulations. You have now successfully replaced a soldered-on PLCC ROM chip on your board with a PLCC socket. You can now swap out the ROM chip as often as you want to or need to. In almost all cases, the board and the ROM chip will survive this procedure if you are careful.

Further resources

• HOWO: replace a PLCC chip with a socket "ghetto style" (tutorial for doing this without desoldering station by cutting the chip)

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