ASP.NET CheckBox Value doesn't change

I have the following code :

<asp:UpdatePanel ID="UpdatePanel3" runat="server" UpdateMode="Conditional" Visible="true" RenderMode="Inline">
    <ContentTemplate> 
       <tr>
            <td>
                 <asp:CheckBox ID="CheckBoxTel" Text="Téléphone" ToolTip="N° de téléphone du client" runat="server" AutoPostBack="true" />
            </td>
       </tr>
    </ContentTemplate>
    <Triggers>
         <asp:AsyncPostBackTrigger ControlID="CheckBoxTel" EventName="CheckedChanged" />                   
    </Triggers>
</asp:UpdatePanel>

I would like to not refresh the page when a checkbox is checked or unchecked that's why I use a trigger but I'm new to update panel and trigger and I'm not sure why when I click on my submit button that refreshes the page, the checkbox keeps unchecked even if I checked it. Do I have to bind something to the button ?

Here is the button code :

<asp:Button ID="Search" runat="server" Text="Search" CssClass="btn btn-primary" OnClick="Search_OnClick" />