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Introduction

This guide provides information on how to solder the various phyCORE-i.MX 8M Mini modules.

Delivery Format

The modules are only shipped in reels. For more information, please contact PHYTEC Sales.

All dimensions and tolerances as per EIA 481 standard.

 i.MX 8M Mini Reel Technical Information

Production Settings

Moisture Sensitivity, Shelf Life, and Storage

The modules are rated MSL 3, so it is required that they are stored adequately before soldering (see IPC/JEDEC J-STD-033C). PHYTEC recommends storing the modules shrink-wrapped in the original packing. If the packaging is opened, store them in humidity reduced storage (rel. humidity < 10%, T < 30°C / 86°F). The shelf life for sealed packaging is 12 months at < 40°C and < 90 % rel. humidity.

Paste Printing

Stencil

• Stencil thickness: 100µm / 4mil
• Stencil alignment: 25% off the smallest pad
• For better durability for mechanical vibrations and shock, the golden edges of the module can be soldered. We did mechanical stress tests without soldered edges and no problems occurred (Shock-Test: 40g, sinusoidal vibrations: 8g at 10 - 150Hz; random noise vibrations: 4g at 10 - 500 Hz). W also did temperature shock tests (750 cycles from -40°C to 125°C) → no problems occurred.

Solder Paste

The following solder paste type has been approved for mounting the module onto a carrier:

• SAC305 (Lead-free: Alpha OM-340 Type 4 or equivalent)

Placement

Dimensions of the Module

The link “phyCORE-i.MX 8M Mini” within the category "Dimensioned Drawing" on the phyCORE‑i.MX 8M Mini download page (https://www.phytec.de/produkt/system-on-modules/phycore-imx-8m-mini-nano-phyboard-polis-download/) leads to the layout data. It is available in different file formats. Use of this data allows integrating the phyCORE-i.MX 8M Mini SOM as a single component into your design.

Coplanarity

The coplanarity measured on the i.MX 8M Mini is<0.003" bow and twist (98% confidence interval). It is important that the carrier board is also coplanar. If the carrier board is thinner then the i.MX 8M Mini, it is recommended that the assembly be supported during the reflow process, i.e. a reflow fixture should be used to minimize the potential bow of the carrier card.

SMT Pick and Place

• Placement Nozzle: Largest nozzle that is available on the machine
• Nozzle Pick Surface: Center of Shield on i.MX 8M Mini SOM
• Placement Speed: Slowest speed for the machine
• Placement alignment: 10% of pad diameter (compensating for module weight and supporting alignment). The module should be placed last as part of the assembly/mounting process to eliminate unexpected shifting.
• Place the SOM at last on the carrier board

SMT Process Parameter Reference

Soldering

Our soldering profiles for the vapor phase soldering is based on J-STD-020E (see below). The liquidus time amounts between 60 s and 90 s, and we recommend a maximum of three soldering processes. The peak body temperature of the populated parts is 260°C.

Classification Profile (J-STD-020E¹, Table 5-2, Page 8):

Note 1:  All temperatures refer to the center of the package, measured on the package body surface that is facing up during assembly reflow (e.g. live-bug). If parts are reflowed in other than the normal live bug assembly reflow orientation (i.e., dead-bug), Tp must be within±2°C of the livebug Tp and still meet the Tc requirements. Otherwise, the profile must be adjusted to achieve the latter. To accurately measure actual peak package body temperatures, refer to JEP140 for recommended thermocouple use.

Note2:  Reflow profiles in this document are for classification / preconditioning and are not meant to specify board assembly profiles. Actual board assembly profiles should be developed based on specific process needs and board designs and should not exceed the parameters in this table. For example, if Tc is 260 °C and time Tp is 30 seconds, this means the following for the supplier and the user:

• For a supplier:   The peak temperature must be at least 260 °C. The time above 255 °C must be at least 30 seconds.
• For a user:   The peak temperature must not exceed 260 °C. The time above 255 °C must not exceed 30 seconds.

Note 3:  All components in the test load must meet the classification profile requirements. 

Note 4:  SMD packages classified to a given moisture sensitivity level by using Procedures or Criteria defined within any previous version of J-STD-020, JESD22-A112 (rescinded), IPC-SM-786 (rescinded) do not need to be reclassified to the current revision unless a change in classification level or a higher peak classification temperature is desired.

Classification Profile (J-STD-020E¹, Figure 5-1, Page 8)

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