Dec19
What is IMC (Intermetallic Compound) in the electronic manufacturing industry？

post on December 19, 2018

What is IMC (Intermetallic Compound) in the electronic manufacturing industry？

What is the IMC, the Intermetallic Compound? We always heard the manufacturing engineer or some of Mechanical Engineer and EE talking about this keyword when discussing soldering quality or electronic component drop issue. So, what is the role of IMC layer in soldering? Does the IMC layer affect soldering strength and solderability? What is the ideal IMC layer thickness?

The IMC is the abbreviation of Inter-Metallic Compound in the electronic manufacturing industry.  The IMC usually grows between the solder alloy and Copeper (Cu) or Nickel (Ni) substrate for the Printed Circuit Board Assembly (PCBA). The IMC is neither a pure metal element nor alloy (Some expert think IMC is a kind of alloy). The IMC is a chemical compound that chemically combined by two or more elements. So, you may see the chemical formula of IMC like Cu6Sn5、Ni3Sn4、AuSn4 ,and so on.

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Process, Soldering     WorkingBear    Views (41,421)     comments (3)
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Dec05
Both solder joint bridging and open solder joint happen at same BGA?

post on December 5, 2018

Is that possible both solder joint bridging and open solder joint defect happen at same BGA (Ball Grid Array) or CSP (Chip Scale Package) device?BGA cry down（電路板則因為TAL(Time Above Liquidous)過長，與迴焊爐的上下爐溫溫差過大，兩相交互作用下形成電路板板邊下彎，造成了所謂的哭臉曲線）

Is that possible for both solder joint bridging and open solder joint defect occur in the same BGA (Ball Grid Array) or CSP (Chip Scale Package) device?

It is rare to observe both solder joint bridging and open solder joint defects simultaneously in a BGA device under normal circumstances, but it is still possible. In cases where the BGA substrate and PCB exhibit a significant deviation in CTE (Coefficient of Thermal Expansion), the BGA substrate may deform with a concave smile-up curve, while the PCB may deform with a convex cry-down curve due to longer TAL (Time Above Liquidus) or significant temperature variation between the upper and lower heaters in the reflow oven.

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Process, Quality, Soldering     WorkingBear    Views (8,178)     comment (0)
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Nov14
How to print solder paste on PC Board and screen printing notices?

post on November 14, 2018

Printing the solder paste on the PCB (Printed Circuit Board) and go through reflow oven to re-melt the solder paste and solder the electronic components on PCB is most common process in today’s electronics manufacturing industry. Printing the solder paste on the PCB just like painting on the wall. The only different is solder paste printing ask more accurately position and must control the solder paste volume on each pad. It requires a certain jig call “stencil”  is a sheet-metal made and have designate aperture on the position that needs to print solder paste.

Almost of current PCB assembly manufacturer apply the “stencil” jig to enhance the solder paste printing process to get more accurately printing position of solder paste and control the solder volume. Once the solder paste print shift from its pad too much then the solder will not joint the electronic component and PCB pad together. The solder paste volume over or less quantity will make solder short or open defect.

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SMT, Soldering     WorkingBear    Views (12,372)     comment (0)
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Jun19
Increase solder paste volume will improve the MLCC capacitor broken?

post on June 19, 2017

MLCC_broken_PCB_side

Recently WorkingBear got complaint from R&D and ask increase the solder paste volume on the MLCC (Multi-Layer Ceramic Capacitor)  component pads to improve the capacitor broken issue. R&D said he had verified that the capacitor’s footprint in the board design is correct and followed manufacturer’s design guidelines. However, looks like there is not enough solder paste to form proper heel fillet on the terminal of capacitor. This insufficient solder paste volume make the solder cracking?

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Design, Manufacture, PCB/FPC/PTF, Quality, Reliability, SMT, Soldering     WorkingBear    Views (6,812)     comment (0)
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Jan05
Comparison between shielding-can directly mount and shielding-clip/frame

post on January 5, 2017

Recently one of my top manager ask to mount the shielding-can or call shielding-cover directly on the Printed Circuit Board to instead of mount the shielding-clip or call shielding-frame on the board first then cover the shieling-can. He said this “new process” is more cheap and can reach better RF (Radiation Frequency) performance. Also most of current popular cell phone board apply this solution.

Well, I must say yes. Directly mount the shielding-can on the board is cheaper and save labor hours as compare it with mount one component (frame or clip) on the board first then install another component (can or cover) to cover it. But this new requirement also got lots of negative feedback from SMT factory and repair center. Because of directly mount shielding-can on board means that repair guy must de-solder the shielding can first before repair the component under the shielding can. It make the repair job more difficult and may give more trouble and damage the board during repair.

Related article: The benefit to use shielding clips to instead of shielding frame

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Design, Manufacture, SMT     WorkingBear    Views (6,881)     comment (0)
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