Why does a laptop motherboard have plastic stuck to it?

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Why does a laptop motherboard have plastic stuck to it?

Postposted on Sun Apr 20, 2014 7:57 am

Took a HP G6000 back that someone threw out in the "give away" bin. Somebody had already taken all the obvious parts - but left the CPU (Athlon X2 TK57) and wireless BCM94311. Took it apart to see how laptops are put together, and I was blown away by all the plastic stuck on it.

I can perhaps understand putting plastic on places where there are user replaceable parts, but why at the back of the CPU socket? What's that orange plastic for anyway?
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Re: Why does a laptop motherboard have plastic stuck to it?

Postposted on Sun Apr 20, 2014 8:36 am

My first guess is that it's to guard against short circuits.
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Re: Why does a laptop motherboard have plastic stuck to it?

Postposted on Sun Apr 20, 2014 8:58 am

That would be my guess as well. As long as you're not covering up something that is going to overheat from lack of airflow, it will improve reliability by helping keep coffee spills, etc. off of the electrical circuitry.
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Re: Why does a laptop motherboard have plastic stuck to it?

Postposted on Sun Apr 20, 2014 9:38 am

The orange plastic is Kapton tape. It is used as an insulator and to hold things in place. The rest of the plastic you see is used to keep things from shorting out when the motherboard and case flex. The black stuck is heavier duty and looks to be over the power supply section. A short here causes fire. The clear stuff all around the CPU keeps the thicker components from coming in contact with the bottom of the case.

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Re: Why does a laptop motherboard have plastic stuck to it?

Postposted on Sun Apr 20, 2014 9:50 am

the orange plastic is probably Kapton tape (generically polyimide film or polyimide tape). It's used in high temperature applications or where chemical resistance is required. The stripe of Kapton tape just next to the connector is probably there to hold the cable down; and, they likely chose Kapton because the PSA on Kapton tapes is generally of higher quality than would be found on the black vinyl electrical tape (layman's terms: it sticks better). The black (vinyl -- probably) is around the edges and over connectors. It would be put there because they were concerned about shorting to the housing or another part of the laptop adjacent to those points. Remember, the inner surfaces of the laptop are probably coated with a conductive material to create an emi shield.
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Re: Why does a laptop motherboard have plastic stuck to it?

Postposted on Sun Apr 20, 2014 12:49 pm

I heard professional PCBs come with an insulating transparent enamel on top. Is that not the case on this board, or were they just making doubly sure the components themselves wouldn't conduct anything to the case?

The black tape is around the video out area (VGA, S-Video).
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Re: Why does a laptop motherboard have plastic stuck to it?

Postposted on Sun Apr 20, 2014 12:56 pm

Crayon Shin Chan wrote:I heard professional PCBs come with an insulating transparent enamel on top. Is that not the case on this board, or were they just making doubly sure the components themselves wouldn't conduct anything to the case?

Unless the board has been conformally coated after assembly (which is expensive, and generally done only for hardware which will be used in harsh environments) the enamel coating only covers copper PCB traces, not the copper pads the components get soldered to, or the solder joints.
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