When I use mobile phone download .docx from my site . Android is work..but IOS can't

this is my HTML <a href="http://example/file/test.docx"></a>

when I click this in web . Android can open Browser to download ,but IOS just open this *.docx file in web

I can't to download in iphone

this is my part of nginx

`

server {
    listen       80;
    server_name  www.qingce.cc;
    location ~^/(js|css|img|fonts|file)/{
    access_log off;
    root    /home/user/public;
    expires 2h;
   }
    location /  {
    proxy_set_header   X-Real-IP $remote_addr;
    proxy_set_header   Host      $http_host;
    proxy_pass         http://127.0.0.1:3001;
    }
    }

`

How to download the file in iphone .PLZ help!