The M905’s LGA assembly example for MtConnect05

The package design of MtM+ M905 is Land Grid Array(LGA) package. The LGA package is a standard flip-chip Ball Grid Array (BGA) shipped with no spheres.

The LGA solder interconnect is formed solely by solder paste applied at board assembly because there are no spheres attached to the LGA. This results in a lower standoff height of approximately 0.06 mm to 0.10 mm, depending on solder paste volume and printed circuit board (PCB) geometry.

Stencil Design

The stencil’s thickness is 100 µm for solder paste of MtConnect05, and opening smaller 10µm than the foot print of M905.

Technical Blueprint

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Print the Solder Paste

Solder paste needs to be screened onto the LGA pads and the part taken through reflow furnace (Surface mount Process simulation test per JEDEC spec “Solderability” JESD22-B102D)m905-smt-solder-paste.jpg

mtconnect05-smt-solder-paste-print.jpg

Placement

 

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m905-smt-xray.001Before the reflow process, examine the X-ray of the M905’s placement. The 52 pads of M905 are square like the blue rectangles in the picture. After printing the solder paste,  they must be in the center of M905’s pads without any overflow. Others objects beyond the blue rectangle like the rounds and big shadows, they are the components inside the M905’s SiP module.

Reflow

Reflow soldering is the most common method of attaching surface mount components to a PCB. The process is to melt the solder and heat the adjoining surfaces, without overheating and damaging the electrical components. The reflow profile describes the ideal temperature curve of the top layer of the PCB.

After the reflow process, the x-ray inspection shows the quality of whole SMT process. The major criteria are:

  • There is no short between any pads of M905.
  • The void should less than 25%.
  • There is no damage inside the module.

m905-smt-xray.after-reflow.jpeg

Different SMT manufacturer

We have made MtConnect05 in serveral manufacturers for examining the quality of SMT production.

m905-smt-xray.cz

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Reduce the Failure Rate

To reduce the failure rate in SMT process, we recommand 3 items need to take care:

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Reflow profile measurement tooling

To handle varies PCB materials and manufacturer’s equipment, You need a measurement tooling to make sure the reflow quality

Performing the recommended reflow profile of solder paste

The solder paste has its own recommend reflow profile by the manufacturer. Use the measurement tooling to make sure that the configuration of reflow oven performs the required temperature of solder paste, will let solder paste works at the appropriate temperature.

Baking process

It is a necessary step before reflow process, to eliminate outgassing of moisture which is absorbed by PCB material when storing. Any moisture will evaporate and make the void failure of the reflow process.

Documentation

We have the assembly guideline with the recommendations of the SMT process. If you need further assistance, please feel free to contact us.

Download guideline